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  • Design for object with optional and modifiable attributtes?

    - by Ikuzen
    I've been using the Builder pattern to create objects with a large number of attributes, where most of them are optional. But up until now, I've defined them as final, as recommended by Joshua Block and other authors, and haven't needed to change their values. I am wondering what should I do though if I need a class with a substantial number of optional but non-final (mutable) attributes? My Builder pattern code looks like this: public class Example { //All possible parameters (optional or not) private final int param1; private final int param2; //Builder class public static class Builder { private final int param1; //Required parameters private int param2 = 0; //Optional parameters - initialized to default //Builder constructor public Builder (int param1) { this.param1 = param1; } //Setter-like methods for optional parameters public Builder param2(int value) { param2 = value; return this; } //build() method public Example build() { return new Example(this); } } //Private constructor private Example(Builder builder) { param1 = builder.param1; param2 = builder.param2; } } Can I just remove the final keyword from the declaration to be able to access the attributes externally (through normal setters, for example)? Or is there a creational pattern that allows optional but non-final attributes that would be better suited in this case?

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  • Recommended design pattern for object with optional and modifiable attributtes? [on hold]

    - by Ikuzen
    I've been using the Builder pattern to create objects with a large number of attributes, where most of them are optional. But up until now, I've defined them as final, as recommended by Joshua Block and other authors, and haven't needed to change their values. I am wondering what should I do though if I need a class with a substantial number of optional but non-final (mutable) attributes? My Builder pattern code looks like this: public class Example { //All possible parameters (optional or not) private final int param1; private final int param2; //Builder class public static class Builder { private final int param1; //Required parameters private int param2 = 0; //Optional parameters - initialized to default //Builder constructor public Builder (int param1) { this.param1 = param1; } //Setter-like methods for optional parameters public Builder param2(int value) { param2 = value; return this; } //build() method public Example build() { return new Example(this); } } //Private constructor private Example(Builder builder) { param1 = builder.param1; param2 = builder.param2; } } Can I just remove the final keyword from the declaration to be able to access the attributes externally (through normal setters, for example)? Or is there a creational pattern that allows optional but non-final attributes that would be better suited in this case?

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  • Project compile perfectly but i get unhandled exception and have no idea why??? any clues?

    - by JB
    get unhandled exception that says: System.NullReferenceException: Object reference not set to an instance of an object. at Eagle_Eye_Class_Finder.GetSchedule.GetDataFromNumber(String ID) in C:\Users\Joshua Banks\Desktop\EET Project\Eagle Eye Class Finder\GetSchedule.cs:line 24 at Eagle_Eye_Class_Finder.Form1.button2_Click(Object sender, EventArgs e) in C:\Users\Joshua Banks\Desktop\EET Project\Eagle Eye Class Finder\Form1.cs:line 196 at System.Windows.Forms.Control.OnClick(EventArgs e) at System.Windows.Forms.Button.OnClick(EventArgs e) at System.Windows.Forms.Button.PerformClick() at System.Windows.Forms.Form.ProcessDialogKey(Keys keyData) at System.Windows.Forms.Control.ProcessDialogKey(Keys keyData) at System.Windows.Forms.TextBoxBase.ProcessDialogKey(Keys keyData) at System.Windows.Forms.Control.PreProcessMessage(Message& msg) at System.Windows.Forms.Control.PreProcessControlMessageInternal(Control target, Message& msg) at System.Windows.Forms.Application.ThreadContext.PreTranslateMessage(MSG& msg) Here is my Get Schedule Class: using System; using System.IO; using System.Data; using System.Text; using System.Drawing; using System.Data.OleDb; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Drawing.Printing; using System.Collections.Generic; namespace Eagle_Eye_Class_Finder { public class GetSchedule { public string GetDataFromNumber(string ID) { IDnumber[] IDnumbers = new IDnumber[3]; foreach (IDnumber IDCandidateMatch in IDnumbers) { if (IDCandidateMatch.ID == ID) { StringBuilder myData = new StringBuilder(); myData.AppendLine(IDCandidateMatch.Name); myData.AppendLine(": "); myData.AppendLine(IDCandidateMatch.ID); myData.AppendLine(IDCandidateMatch.year); myData.AppendLine(IDCandidateMatch.class1); myData.AppendLine(IDCandidateMatch.class2); myData.AppendLine(IDCandidateMatch.class3); myData.AppendLine(IDCandidateMatch.class4); //return myData; return myData.ToString(); } } return ""; } public GetSchedule() { IDnumber[] IDnumbers = new IDnumber[3]; IDnumbers[0] = new IDnumber() { Name = "Joshua Banks", ID = "900456317", year = "Senior", class1 = "TEET 4090", class2 = "TEET 3020", class3 = "TEET 3090", class4 = "TEET 4290" }; IDnumbers[1] = new IDnumber() { Name = "Sean Ward", ID = "900456318", year = "Junior", class1 = "ENGNR 4090", class2 = "ENGNR 3020", class3 = "ENGNR 3090", class4 = "ENGNR 4290" }; IDnumbers[2] = new IDnumber() { Name = "Terrell Johnson", ID = "900456319", year = "Sophomore", class1 = "BUS 4090", class2 = "BUS 3020", class3 = "BUS 3090", class4 = "BUS 4290" }; } public class IDnumber { public string Name { get; set; } public string ID { get; set; } public string year { get; set; } public string class1 { get; set; } public string class2 { get; set; } public string class3 { get; set; } public string class4 { get; set; } public static void ProcessNumber(IDnumber myNum) { StringBuilder myData = new StringBuilder(); myData.AppendLine(myNum.Name); myData.AppendLine(": "); myData.AppendLine(myNum.ID); myData.AppendLine(myNum.year); myData.AppendLine(myNum.class1); myData.AppendLine(myNum.class2); myData.AppendLine(myNum.class3); myData.AppendLine(myNum.class4); MessageBox.Show(myData.ToString()); } } } } Here is my Form 1 class: using System; using System.IO; using System.Data; using System.Text; using System.Drawing; using System.Data.OleDb; using System.Collections; using System.Windows.Forms; using System.ComponentModel; using System.Drawing.Printing; using System.Collections.Generic; namespace Eagle_Eye_Class_Finder { /// This form is the entry form, it is the first form the user will see when the app is run. /// public class Form1 : System.Windows.Forms.Form { private System.Windows.Forms.TextBox textBox1; private System.Windows.Forms.ProgressBar progressBar1; private System.Windows.Forms.PictureBox pictureBox1; private System.Windows.Forms.Button button2; private System.Windows.Forms.DateTimePicker dateTimePicker1; private IContainer components; private Timer timer1; private BindingSource form1BindingSource; public static Form Mainform = null; // creates new instance of second form YOURCLASSSCHEDULE SecondForm = new YOURCLASSSCHEDULE(); public Form1() { InitializeComponent(); // TODO: Add any constructor code after InitializeComponent call } /// Clean up any resources being used. protected override void Dispose(bool disposing) { if (disposing) { if (components != null) { components.Dispose(); } } base.Dispose(disposing); } #region Windows Form Designer generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { this.components = new System.ComponentModel.Container(); System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(Form1)); this.textBox1 = new System.Windows.Forms.TextBox(); this.progressBar1 = new System.Windows.Forms.ProgressBar(); this.pictureBox1 = new System.Windows.Forms.PictureBox(); this.button2 = new System.Windows.Forms.Button(); this.dateTimePicker1 = new System.Windows.Forms.DateTimePicker(); this.timer1 = new System.Windows.Forms.Timer(this.components); this.form1BindingSource = new System.Windows.Forms.BindingSource(this.components); ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).BeginInit(); ((System.ComponentModel.ISupportInitialize)(this.form1BindingSource)).BeginInit(); this.SuspendLayout(); // // textBox1 // this.textBox1.BackColor = System.Drawing.SystemColors.ActiveCaption; this.textBox1.DataBindings.Add(new System.Windows.Forms.Binding("Text", this.form1BindingSource, "Text", true, System.Windows.Forms.DataSourceUpdateMode.OnValidation, null, "900456317")); this.textBox1.Location = new System.Drawing.Point(328, 280); this.textBox1.Name = "textBox1"; this.textBox1.Size = new System.Drawing.Size(208, 20); this.textBox1.TabIndex = 2; this.textBox1.TextChanged += new System.EventHandler(this.textBox1_TextChanged); // // progressBar1 // this.progressBar1.Location = new System.Drawing.Point(258, 410); this.progressBar1.MarqueeAnimationSpeed = 10; this.progressBar1.Name = "progressBar1"; this.progressBar1.Size = new System.Drawing.Size(344, 8); this.progressBar1.TabIndex = 3; this.progressBar1.Click += new System.EventHandler(this.progressBar1_Click); // // pictureBox1 // this.pictureBox1.BackColor = System.Drawing.SystemColors.ControlLightLight; this.pictureBox1.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; this.pictureBox1.Image = ((System.Drawing.Image)(resources.GetObject("pictureBox1.Image"))); this.pictureBox1.Location = new System.Drawing.Point(680, 400); this.pictureBox1.Name = "pictureBox1"; this.pictureBox1.Size = new System.Drawing.Size(120, 112); this.pictureBox1.TabIndex = 4; this.pictureBox1.TabStop = false; this.pictureBox1.Click += new System.EventHandler(this.pictureBox1_Click); // // button2 // this.button2.Font = new System.Drawing.Font("Mistral", 15.75F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.button2.Image = ((System.Drawing.Image)(resources.GetObject("button2.Image"))); this.button2.Location = new System.Drawing.Point(699, 442); this.button2.Name = "button2"; this.button2.Size = new System.Drawing.Size(78, 28); this.button2.TabIndex = 5; this.button2.Text = "OK"; this.button2.Click += new System.EventHandler(this.button2_Click); // // dateTimePicker1 // this.dateTimePicker1.Location = new System.Drawing.Point(336, 104); this.dateTimePicker1.Name = "dateTimePicker1"; this.dateTimePicker1.Size = new System.Drawing.Size(200, 20); this.dateTimePicker1.TabIndex = 6; this.dateTimePicker1.ValueChanged += new System.EventHandler(this.dateTimePicker1_ValueChanged); // // timer1 // this.timer1.Tick += new System.EventHandler(this.timer1_Tick); // // form1BindingSource // this.form1BindingSource.DataSource = typeof(Eagle_Eye_Class_Finder.Form1); // // Form1 // this.AcceptButton = this.button2; this.AutoScaleBaseSize = new System.Drawing.Size(5, 13); this.BackgroundImage = ((System.Drawing.Image)(resources.GetObject("$this.BackgroundImage"))); this.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Stretch; this.ClientSize = new System.Drawing.Size(856, 556); this.Controls.Add(this.dateTimePicker1); this.Controls.Add(this.button2); this.Controls.Add(this.pictureBox1); this.Controls.Add(this.progressBar1); this.Controls.Add(this.textBox1); this.Name = "Form1"; this.Text = "Eagle Eye Class Finder"; this.Load += new System.EventHandler(this.Form1_Load); ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).EndInit(); ((System.ComponentModel.ISupportInitialize)(this.form1BindingSource)).EndInit(); this.ResumeLayout(false); this.PerformLayout(); } #endregion /// The main entry point for the application. [STAThread] static void Main() { Application.Run(new Form1()); } public void Form1_Load(object sender, System.EventArgs e) { } public void textBox1_TextChanged(object sender, System.EventArgs e) { //allows only numbers to be entered in textbox string Str = textBox1.Text.Trim(); double Num; bool isNum = double.TryParse(Str, out Num); if (isNum) Console.ReadLine(); else MessageBox.Show("Enter A Valid ID Number!"); } public void button2_Click(object sender, System.EventArgs e) { string text = textBox1.Text; Mainform = this; this.Hide(); GetSchedule myScheduleFinder = new GetSchedule(); string result = myScheduleFinder.GetDataFromNumber(text); if (!string.IsNullOrEmpty(result)) { MessageBox.Show(result); } else { MessageBox.Show("Enter A Valid ID Number!"); } } public void dateTimePicker1_ValueChanged(object sender, System.EventArgs e) { } public void pictureBox1_Click(object sender, System.EventArgs e) { } public void progressBar1_Click(object sender, EventArgs e) { //this.progressBar1 = new System.progressBar1(); //progressBar1.Maximum = 200; //progressBar1.Minimum = 0; //progressBar1.Step = 20; } private void timer1_Tick(object sender, EventArgs e) { //if (progressBar1.Value >= 200 ) //{ //progressBar1.Value = 0; //} //return; //} //progressBar1.Value != 20; } } } here is my form 2 class: using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; namespace Eagle_Eye_Class_Finder { /// /// Summary description for Form2. /// public class YOURCLASSSCHEDULE : System.Windows.Forms.Form { public System.Windows.Forms.LinkLabel linkLabel1; public System.Windows.Forms.LinkLabel linkLabel2; public System.Windows.Forms.LinkLabel linkLabel3; public System.Windows.Forms.LinkLabel linkLabel4; private Button button1; /// Required designer variable. public System.ComponentModel.Container components = null; public YOURCLASSSCHEDULE() { // InitializeComponent(); // TODO: Add any constructor code after InitializeComponent call } /// Clean up any resources being used. protected override void Dispose(bool disposing) { if (disposing) { if (components != null) { components.Dispose(); } } base.Dispose(disposing); } #region Windows Form Designer generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(YOURCLASSSCHEDULE)); this.linkLabel1 = new System.Windows.Forms.LinkLabel(); this.linkLabel2 = new System.Windows.Forms.LinkLabel(); this.linkLabel3 = new System.Windows.Forms.LinkLabel(); this.linkLabel4 = new System.Windows.Forms.LinkLabel(); this.button1 = new System.Windows.Forms.Button(); this.SuspendLayout(); // // linkLabel1 // this.linkLabel1.BackColor = System.Drawing.SystemColors.ActiveCaption; this.linkLabel1.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; this.linkLabel1.Font = new System.Drawing.Font("Times New Roman", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.linkLabel1.LinkArea = new System.Windows.Forms.LinkArea(0, 7); this.linkLabel1.LinkBehavior = System.Windows.Forms.LinkBehavior.HoverUnderline; this.linkLabel1.Location = new System.Drawing.Point(41, 123); this.linkLabel1.Name = "linkLabel1"; this.linkLabel1.Size = new System.Drawing.Size(288, 32); this.linkLabel1.TabIndex = 1; this.linkLabel1.TabStop = true; this.linkLabel1.Text = "Class 1"; this.linkLabel1.TextAlign = System.Drawing.ContentAlignment.MiddleCenter; this.linkLabel1.LinkClicked += new System.Windows.Forms.LinkLabelLinkClickedEventHandler(this.linkLabel1_LinkClicked); // // linkLabel2 // this.linkLabel2.BackColor = System.Drawing.SystemColors.ActiveCaption; this.linkLabel2.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; this.linkLabel2.Font = new System.Drawing.Font("Times New Roman", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.linkLabel2.LinkBehavior = System.Windows.Forms.LinkBehavior.HoverUnderline; this.linkLabel2.Location = new System.Drawing.Point(467, 123); this.linkLabel2.Name = "linkLabel2"; this.linkLabel2.Size = new System.Drawing.Size(288, 32); this.linkLabel2.TabIndex = 2; this.linkLabel2.TabStop = true; this.linkLabel2.Text = "Class 2"; this.linkLabel2.TextAlign = System.Drawing.ContentAlignment.MiddleCenter; this.linkLabel2.VisitedLinkColor = System.Drawing.Color.Navy; this.linkLabel2.LinkClicked += new System.Windows.Forms.LinkLabelLinkClickedEventHandler(this.linkLabel2_LinkClicked); // // linkLabel3 // this.linkLabel3.BackColor = System.Drawing.SystemColors.ActiveCaption; this.linkLabel3.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; this.linkLabel3.Font = new System.Drawing.Font("Times New Roman", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.linkLabel3.LinkBehavior = System.Windows.Forms.LinkBehavior.HoverUnderline; this.linkLabel3.Location = new System.Drawing.Point(41, 311); this.linkLabel3.Name = "linkLabel3"; this.linkLabel3.Size = new System.Drawing.Size(288, 32); this.linkLabel3.TabIndex = 3; this.linkLabel3.TabStop = true; this.linkLabel3.Text = "Class 3"; this.linkLabel3.TextAlign = System.Drawing.ContentAlignment.MiddleCenter; this.linkLabel3.LinkClicked += new System.Windows.Forms.LinkLabelLinkClickedEventHandler(this.linkLabel3_LinkClicked); // // linkLabel4 // this.linkLabel4.BackColor = System.Drawing.SystemColors.ActiveCaption; this.linkLabel4.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; this.linkLabel4.Font = new System.Drawing.Font("Times New Roman", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.linkLabel4.LinkBehavior = System.Windows.Forms.LinkBehavior.HoverUnderline; this.linkLabel4.Location = new System.Drawing.Point(467, 311); this.linkLabel4.Name = "linkLabel4"; this.linkLabel4.Size = new System.Drawing.Size(288, 32); this.linkLabel4.TabIndex = 4; this.linkLabel4.TabStop = true; this.linkLabel4.Text = "Class 4"; this.linkLabel4.TextAlign = System.Drawing.ContentAlignment.MiddleCenter; this.linkLabel4.LinkClicked += new System.Windows.Forms.LinkLabelLinkClickedEventHandler(this.linkLabel4_LinkClicked); // // button1 // this.button1.BackColor = System.Drawing.SystemColors.ActiveCaptionText; this.button1.FlatAppearance.BorderColor = System.Drawing.Color.FromArgb(((int)(((byte)(0)))), ((int)(((byte)(0)))), ((int)(((byte)(64))))); this.button1.FlatStyle = System.Windows.Forms.FlatStyle.Popup; this.button1.Font = new System.Drawing.Font("Pristina", 12F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.button1.ForeColor = System.Drawing.SystemColors.ActiveCaption; this.button1.ImageAlign = System.Drawing.ContentAlignment.TopCenter; this.button1.Location = new System.Drawing.Point(358, 206); this.button1.Name = "button1"; this.button1.Size = new System.Drawing.Size(101, 25); this.button1.TabIndex = 5; this.button1.Text = "Go Back"; this.button1.UseVisualStyleBackColor = false; this.button1.Click += new System.EventHandler(this.button1_Click); // // YOURCLASSSCHEDULE // this.AutoScaleBaseSize = new System.Drawing.Size(6, 15); this.BackgroundImage = ((System.Drawing.Image)(resources.GetObject("$this.BackgroundImage"))); this.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Stretch; this.ClientSize = new System.Drawing.Size(790, 482); this.Controls.Add(this.button1); this.Controls.Add(this.linkLabel4); this.Controls.Add(this.linkLabel3); this.Controls.Add(this.linkLabel2); this.Controls.Add(this.linkLabel1); this.Font = new System.Drawing.Font("OldDreadfulNo7 BT", 8.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.Name = "YOURCLASSSCHEDULE"; this.Text = "Your Classes"; this.Load += new System.EventHandler(this.Form2_Load); this.ResumeLayout(false); } #endregion public void Form2_Load(object sender, System.EventArgs e) { // if (text == "900456317") // { //} } public void linkLabel1_LinkClicked(object sender, System.Windows.Forms.LinkLabelLinkClickedEventArgs e) { System.Diagnostics.Process.Start("http://www.georgiasouthern.edu/map/"); } private void linkLabel2_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e) { System.Diagnostics.Process.Start("http://www.georgiasouthern.edu/map/"); } private void linkLabel3_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e) { System.Diagnostics.Process.Start("http://www.georgiasouthern.edu/map/"); } private void linkLabel4_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e) { System.Diagnostics.Process.Start("http://www.georgiasouthern.edu/map/"); } private void button1_Click(object sender, EventArgs e) { Form1 form1 = new Form1(); form1.Show(); this.Hide(); } } }

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  • Object Reference is required for non static field, method, or property

    - by JB
    using System; using System.IO; using System.Data; using System.Text; using System.Drawing; using System.Data.OleDb; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Drawing.Printing; using System.Collections.Generic; namespace Eagle_Eye_Class_Finder { public class GetSchedule { public GetSchedule() { IDnumber[] IDnumbers = new IDnumber[3]; IDnumbers[0] = new IDnumber() { Name = "Joshua Banks", ID = "900456317", year = "Senior", class1 = "TEET 4090", class2 = "TEET 3020", class3 = "TEET 3090", class4 = "TEET 4290" }; IDnumbers[1] = new IDnumber() { Name = "Sean Ward", ID = "900456318", year = "Junior", class1 = "ENGNR 4090", class2 = "ENGNR 3020", class3 = "ENGNR 3090", class4 = "ENGNR 4290" }; IDnumbers[2] = new IDnumber() { Name = "Terrell Johnson", ID = "900456319", year = "Sophomore", class1 = "BUS 4090", class2 = "BUS 3020", class3 = "BUS 3090", class4 = "BUS 4290" }; } public class IDnumber { public string Name { get; set; } public string ID { get; set; } public string year { get; set; } public string class1 { get; set; } public string class2 { get; set; } public string class3 { get; set; } public string class4 { get; set; } public static void ProcessNumber(IDnumber myNum) { StringBuilder myData = new StringBuilder(); myData.AppendLine(IDnumber.Name); myData.AppendLine(": "); myData.AppendLine(IDnumber.ID); myData.AppendLine(IDnumber.year); myData.AppendLine(IDnumber.class1); myData.AppendLine(IDnumber.class2); myData.AppendLine(IDnumber.class3); myData.AppendLine(IDnumber.class4); MessageBox.Show(myData); } public string GetDataFromNumber(string ID) { foreach (IDnumber idCandidateMatch in IDnumbers) { if (IDCandidateMatch.ID == ID) { StringBuilder myData = new StringBuilder(); myData.AppendLine(IDnumber.Name); myData.AppendLine(": "); myData.AppendLine(IDnumber.ID); myData.AppendLine(IDnumber.year); myData.AppendLine(IDnumber.class1); myData.AppendLine(IDnumber.class2); myData.AppendLine(IDnumber.class3); myData.AppendLine(IDnumber.class4); return myData; } } return ""; } } } }using System; using System.IO; using System.Data; using System.Text; using System.Drawing; using System.Data.OleDb; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Drawing.Printing; using System.Collections.Generic; namespace Eagle_Eye_Class_Finder { public class GetSchedule { public GetSchedule() { IDnumber[] IDnumbers = new IDnumber[3]; IDnumbers[0] = new IDnumber() { Name = "Joshua Banks", ID = "900456317", year = "Senior", class1 = "TEET 4090", class2 = "TEET 3020", class3 = "TEET 3090", class4 = "TEET 4290" }; IDnumbers[1] = new IDnumber() { Name = "Sean Ward", ID = "900456318", year = "Junior", class1 = "ENGNR 4090", class2 = "ENGNR 3020", class3 = "ENGNR 3090", class4 = "ENGNR 4290" }; IDnumbers[2] = new IDnumber() { Name = "Terrell Johnson", ID = "900456319", year = "Sophomore", class1 = "BUS 4090", class2 = "BUS 3020", class3 = "BUS 3090", class4 = "BUS 4290" }; } public class IDnumber { public string Name { get; set; } public string ID { get; set; } public string year { get; set; } public string class1 { get; set; } public string class2 { get; set; } public string class3 { get; set; } public string class4 { get; set; } public static void ProcessNumber(IDnumber myNum) { StringBuilder myData = new StringBuilder(); myData.AppendLine(IDnumber.Name); myData.AppendLine(": "); myData.AppendLine(IDnumber.ID); myData.AppendLine(IDnumber.year); myData.AppendLine(IDnumber.class1);// i get it for all of these myData.AppendLine(IDnumber.class2); myData.AppendLine(IDnumber.class3); myData.AppendLine(IDnumber.class4); MessageBox.Show(myData); } public string GetDataFromNumber(string ID) { foreach (IDnumber idCandidateMatch in IDnumbers) { if (IDCandidateMatch.ID == ID) { StringBuilder myData = new StringBuilder(); myData.AppendLine(IDnumber.Name); myData.AppendLine(": "); myData.AppendLine(IDnumber.ID); myData.AppendLine(IDnumber.year); myData.AppendLine(IDnumber.class1); myData.AppendLine(IDnumber.class2); myData.AppendLine(IDnumber.class3); myData.AppendLine(IDnumber.class4); return myData; } } return ""; } } } }

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  • Trying to inherit variable "text" from Form 1 for use in Form 2????

    - by JB
    I have a Form 1 as listed below, im trying to inherit the variable text from it so i can compare is value in an if statement so i can output the file specified for that id number in Form 2...is this possible??? Form 1, where variable is being used: public void button2_Click(object sender, System.EventArgs e) { timer1.Enabled = true; string text = textBox1.Text; Mainform = this; this.Hide(); } Form 2 where im trying to use the variable: if (text == "900456318") { System.Diagnostics.Process.Start("C:\\Users\\Joshua Banks\\Desktop\\Downtown_atlanta_night"); } }

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  • Why use I-prefix for interfaces in Java?

    - by Lars Andren
    Is there some reason why people use I-prefix for interfaces in Java? It seems to be a C#-convention spilling over. For C# it makes sense, as the answers to this question explains. However, for Java a class declaration clearly states which class that is extended and which interfaces that are implemented: public class Crow extends Animal implements Bird I think Joshua Bloch didn't suggest this in Effective Java, and I think he usually makes a lot of sense. I get the I-verbing as presented in an answer to the question above, but is there some other use with this convention for Java?

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  • Equivalent of Bloch's Effective Java for C#

    - by Elliot Vargas
    I've jumped into the C# bandwagon and was wondering if there's an equivalent of Joshua Bloch's Effective Java for the C# world. I've already being able to apply some Java knowledge to C# given their similarity but I'm interested in knowledge to make the most effective use of C# specific features. For example, Generics are not implemented equally in Java and C#, so it's not clear to me if the Java Generic "techniques" will work in C# as well. I'm mostly interested in C# 3.0. That is (of course) unless you guys think I would benefit for looking into versions 1 and 2 features.

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  • Silverlight Cream for April 08, 2010 -- #834

    - by Dave Campbell
    In this Issue: Michael Washington, Phil Middlemiss, Yochay Kiriaty, Giorgetti Alessandro, Mike Snow, John Papa, SilverLaw, smartyP, and Pete Brown. Shoutouts: Steve Wortham sent me a link to his RegEx tool that is written in Silverlight... definitely worth a look: Introducing Code Hinting for Regular Expressions Joshua Blake posted his MIX10 materials: MIX10 NUI session sample code From SilverlightCream.com: Silverlight MVVM: An (Overly) Simplified Explanation Michael Washington has a tutorial up for getting your arms (and head) around MVVM and Silverlight, and Blend too. A Chrome and Glass Theme - Part 3 Phil Middlemiss has part 3 up of his tutorial series on building an awesome theme for Silverlight... he's styling the textbox and checkbox this time around, and improving the button too Automatic Rotation Support or Automatic Multi-Orientation Layout Support for Windows Phone Yochay Kiriaty is giving up some WP7 goodness with his post on Multi-Orientation Layout Support ... yeah I had to say it twice myself :) good links and all the code in addition to the good blog post Silverlight Navigation Framework: resolve the pages using an IoC container Giorgetti Alessandro has some pretty cool code up as a proof of concept of using an IoC container with the Navigation Framework of Silverlight 4. Silverlight Tip of the Day No. 109 – Attach to Process Debugging Mike Snow is back doing Tips of the Day... and number 109 is showing how to attach the debugger to a running Silverlight app. Silverlight TV 20: Community Driven Development with WCF RIA Services In his latest Silverlight TV episode, John Papa talks with Jeff Handley about RIA Services, and how feedback from the community helped shape the product. ChildWindowMouseScrollResizeBehavior - Silverlight 3 SilverLaw has a new Behavior up at the Expression Gallery that gives you resizing on a ChildWindow using the Mouse Wheel. Creating a Windows Phone 7 Metro Style Pivot Application [Part 3] smartyP has the 3rd and final episode for his WP7 Pivot up, and this one includes not only the source but a video tutorial. Layout Rounding Pete Brown talks about Layout Rounding and it has nothing to do with rounding corners... it has to do with rounding off where your objects get placed pixel-wise ... I've blogged about this seemingly-anti-aliasing more than once... Pete has the real answer Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • Speaking at Mix11

    - by Dennis Vroegop
    In April Microsoft will hold the next MIX event. MIX was usually targeted at web designers and developers but has grown over the years to be more a general conference focused on the web and devices. In other words: everything the normal consumer might encounter. It’s not your typical developers conference, although you’ll find many developers there as well. But next to the developers you’ll probably run into designers and user experience specialists as well. This year I am proud to say that I will be one of the people presenting there. Together with all the Surface MVP’s in the world (sounds impressive, but there are only 7 of us) we’ll host a panel discussion on all things Surface, NUI and everything else that matches those subjects. Here’s what the abstract says: The Natural User Interface (NUI) is a hot topic that generates a lot of excitement, but there are only a handful of companies doing real innovation with NUIs and most of the practical experience in the NUI style of design and development is limited to a small number of experts. The Microsoft Surface MVPs are a subset of these experts that have extensive real-world experience with Microsoft Surface and other NUI devices. This session is a panel featuring the Microsoft Surface MVPs and an unfiltered discussion with each other and the audience about the state of the art in NUI design and development. We will share our experiences and ideas, discuss what we think NUI will look like in the near future, and back up our statements with cutting-edge demonstrations prepared by the panelists involving combinations of Microsoft Surface 2.0, Kinect, and Windows Phone 7. We, as Surface MVPs think we are more than just Surface oriented. We like to think we are more NUI MVP’s. But since that’s not a technology with Microsoft you can’t actually become a NUI MVP so Surface is the one that comes the closest. We are currently working on the details of our session but believe me: it will blow you away. Several people we talked to have said this could potentially be the best session of Mix. Quite a challenge, but we’re up for it! Of course I won’t be telling you exactly what we’re going to do in Las Vegas but rest assured that when you visit our session you’ll leave with a lot of new ideas and hopefully be inspired to bring into practice what you’ve seen. Even if the technology we’ll show you isn’t readily available yet. So, if you are in Las Vegas between April 12th and 14th, please join Joshua Blake, Neil Roodyn, Rick Barraza, Bart Roozendaal, Josh Santangelo, Nicolas Calvi and myself for some NUI fun! See you in Vegas! Tags van Technorati: mix11,las vegas,surface,nui,kinecct

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  • Static factory pattern with EJB3/JBoss

    - by purecharger
    I'm fairly new to EJBs and full blown application servers like JBoss, having written and worked with special purpose standalone Java applications for most of my career, with limited use of JEE. I'm wondering about the best way to adapt a commonly used design pattern to EJB3 and JBoss: the static factory pattern. In fact this is Item #1 in Joshua Bloch's Effective Java book (2nd edition) I'm currently working with the following factory: public class CredentialsProcessorFactory { private static final Log log = LogFactory.getLog(CredentialsProcessorFactory.class); private static Map<CredentialsType, CredentialsProcessor> PROCESSORS = new HashMap<CredentialsType, CredentialsProcessor>(); static { PROCESSORS.put(CredentialsType.CSV, new CSVCredentialsProcessor()); } private CredentialsProcessorFactory() {} public static CredentialsProcessor getProcessor(CredentialsType type) { CredentialsProcessor p = PROCESSORS.get(type); if(p == null) throw new IllegalArgumentException("No CredentialsProcessor registered for type " + type.toString()); return p; } However, in the implementation classes of CredentialsProcessor, I require injected resources such as a PersistenceContext, so I have made the CredentialsProcessor interface a @Local interface, and each of the impl's marked with @Stateless. Now I can look them up in JNDI and use the injected resources. But now I have a disconnect because I am not using the factory anymore. My first thought was to change the getProcessor(CredentialsType) method to do a JNDI lookup and return the SLSB instance that is required, but then I need to configure and pass the proper qualified JNDI name. Before I go down that path, I wanted to do more research on accepted practices. How is this design pattern treated in EJB3 / JEE?

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  • Why does using Collections.emptySet() with generics work in assignment but not as a method parameter

    - by Karl von L
    So, I have a class with a constructor like this: public FilterList(Set<Integer> labels) { ... } and I want to construct a new FilterList object with an empty set. Following Joshua Bloch's advice in his book Effective Java, I don't want to create a new object for the empty set; I'll just use Collections.emptySet() instead: FilterList emptyList = new FilterList(Collections.emptySet()); This gives me an error, complaining that java.util.Set<java.lang.Object> is not a java.util.Set<java.lang.Integer>. OK, how about this: FilterList emptyList = new FilterList((Set<Integer>)Collections.emptySet()); This also gives me an error! Ok, how about this: Set<Integer> empty = Collections.emptySet(); FilterList emptyList = new FilterList(empty); Hey, it works! But why? After all, Java doesn't have type inference, which is why you get an unchecked conversion warning if you do Set<Integer> foo = new TreeSet() instead of Set<Integer> foo = new TreeSet<Integer>(). But Set<Integer> empty = Collections.emptySet(); works without even a warning. Why is that?

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  • Creation of Objects: Constructors or Static Factory Methods

    - by Rachel
    I am going through Effective Java and some of my things which I consider as standard are not suggested by the book, for instance creation of object, I was under the impression that constructors are the best way of doing it and books says we should make use of static factory methods, I am not able to few some advantages and so disadvantages and so am asking this question, here are the benefits of using it. Advantages: One advantage of static factory methods is that, unlike constructors, they have names. A second advantage of static factory methods is that, unlike constructors, they are not required to create a new object each time they’re invoked. A third advantage of static factory methods is that, unlike constructors, they can return an object of any subtype of their return type. A fourth advantage of static factory methods is that they reduce the verbosity of creating parameterized type instances. I am not able to understand this advantage and would appreciate if someone can explain this point Disadvantages: The main disadvantage of providing only static factory methods is that classes without public or protected constructors cannot be subclassed. A second disadvantage of static factory methods is that they are not readily distinguishable from other static methods.I am not getting this point and so would really appreciate some explanation. Reference: Effective Java, Joshua Bloch, Edition 2, pg: 5-10 Also, How to decide to use whether to go for Constructor or Static Factory Method for Object Creation ?

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  • post increment operator java

    - by srandpersonia
    I can't make heads or tails of the following code from "java puzzlers" by joshua bloch. public class Test22{ public static void main(String args[]){ int j=0; for(int i=0;i<100;i++){ j=j++; } System.out.println(j); //prints 0 int a=0,b=0; a=b++; System.out.println(a); System.out.println(b); //prints 1 } } I can't get the part where j prints 0. According to the author, j=j++ is similar to temp=j; j=j+1; j=temp; But a=b++ makes b 1. So it should've evaluated like this, a=b b=b+1 By following the same logic, shouldn't j=j++ be evaluated as, j=j j=j+1 Where does the temp come into picture here? Any explanations would be much appreciated. << I'm breaking my head over this. ;) Thanks in advance.

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  • Why is Linux choosing the wrong source ip address

    - by Scheintod
    and what to do to let it choose the right one? This all happens inside an OpenVZ container: The Host is Debian/Wheezy with Redhat/OpenVZ Kernel: root@mycl2:~# uname -a Linux mycl2 2.6.32-openvz-042stab081.5-amd64 #1 SMP Mon Sep 30 16:40:27 MSK 2013 x86_64 GNU/Linux The container has two (virtual) network interfaces. One in public and one in private address-space: root@mycl2:~# ifconfig lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) venet0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:127.0.0.2 P-t-P:127.0.0.2 Bcast:0.0.0.0 Mask:255.255.255.255 UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1 RX packets:475 errors:0 dropped:0 overruns:0 frame:0 TX packets:775 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:32059 (31.3 KiB) TX bytes:56309 (54.9 KiB) venet0:0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:80.123.123.29 P-t-P:80.123.123.29 Bcast:80.123.123.29 Mask:255.255.255.255 UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1 venet0:1 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:10.0.1.29 P-t-P:10.0.1.29 Bcast:10.0.1.29 Mask:255.255.255.255 UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1 The route to the private network is set manually: root@mycl2:~# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 venet0 0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 venet0 Tring to ping others on the private network leads to the wrong source address been choosen: root@mycl2:~# ip route get 10.0.1.26 10.0.1.26 dev venet0 src 80.123.123.29 cache mtu 1500 advmss 1460 hoplimit 64 Why is this and what can I do about it? EDIT: If I create the route with (thanks to Joshua) ip route add 10.0.0.0/8 dev venet0 src 10.0.1.29 it is working. But according to man ip-route the src parameter should only set the source-ip if this route is chosen. But if this route is chosen then the source-ip would be that anyway.

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  • Java Builder pattern with Generic type bounds

    - by I82Much
    Hi all, I'm attempting to create a class with many parameters, using a Builder pattern rather than telescoping constructors. I'm doing this in the way described by Joshua Bloch's Effective Java, having private constructor on the enclosing class, and a public static Builder class. The Builder class ensures the object is in a consistent state before calling build(), at which point it delegates the construction of the enclosing object to the private constructor. Thus public class Foo { // Many variables private Foo(Builder b) { // Use all of b's variables to initialize self } public static final class Builder { public Builder(/* required variables */) { } public Builder var1(Var var) { // set it return this; } public Foo build() { return new Foo(this); } } } I then want to add type bounds to some of the variables, and thus need to parametrize the class definition. I want the bounds of the Foo class to be the same as that of the Builder class. public class Foo<Q extends Quantity> { private final Unit<Q> units; // Many variables private Foo(Builder<Q> b) { // Use all of b's variables to initialize self } public static final class Builder<Q extends Quantity> { private Unit<Q> units; public Builder(/* required variables */) { } public Builder units(Unit<Q> units) { this.units = units; return this; } public Foo build() { return new Foo<Q>(this); } } } This compiles fine, but the compiler is allowing me to do things I feel should be compiler errors. E.g. public static final Foo.Builder<Acceleration> x_Body_AccelField = new Foo.Builder<Acceleration>() .units(SI.METER) .build(); Here the units argument is not Unit<Acceleration> but Unit<Length>, but it is still accepted by the compiler. What am I doing wrong here? I want to ensure at compile time that the unit types match up correctly.

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  • I am using a constructor for my array but why is it saying i need a return type?

    - by JB
    using System; using System.IO; using System.Data; using System.Text; using System.Drawing; using System.Data.OleDb; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Drawing.Printing; using System.Collections.Generic; namespace Eagle_Eye_Class_Finder { public class GetSchedule { public class IDnumber { public string Name { get; set; } public string ID { get; set; } public string year { get; set; } public string class1 { get; set; } public string class2 { get; set; } public string class3 { get; set; } public string class4 { get; set; } IDnumber[] IDnumbers = new IDnumber[3]; public GetSchedule() //here i get an error saying method must have a return type??? { IDnumbers[0] = new IDnumber() { Name = "Joshua Banks",ID = "900456317", year = "Senior", class1 = "TEET 4090", class2 = "TEET 3020", class3 = "TEET 3090", class4 = "TEET 4290" }; IDnumbers[1] = new IDnumber() { Name = "Sean Ward", ID = "900456318", year = "Junior", class1 = "ENGNR 4090", class2 = "ENGNR 3020", class3 = "ENGNR 3090", class4 = "ENGNR 4290" }; IDnumbers[2] = new IDnumber() { Name = "Terrell Johnson",ID = "900456319",year = "Sophomore", class1 = "BUS 4090", class2 = "BUS 3020", class3 = "BUS 3090", class4 = "BUS 4290" }; } static void ProcessNumber(IDnumber myNum) { StringBuilder myData = new StringBuilder(); myData.AppendLine(IDnumber.Name); myData.AppendLine(": "); myData.AppendLine(IDnumber.ID); myData.AppendLine(IDnumber.year); myData.AppendLine(IDnumber.class1); myData.AppendLine(IDnumber.class2); myData.AppendLine(IDnumber.class3); myData.AppendLine(IDnumber.class4); MessageBox.Show(myData); } public string GetDataFromNumber(string ID) { foreach (IDnumber idCandidateMatch in IDnumbers) { if (IDCandidateMatch.ID == ID) { StringBuilder myData = new StringBuilder(); myData.AppendLine(IDnumber.Name); myData.AppendLine(": "); myData.AppendLine(IDnumber.ID); myData.AppendLine(IDnumber.year); myData.AppendLine(IDnumber.class1); myData.AppendLine(IDnumber.class2); myData.AppendLine(IDnumber.class3); myData.AppendLine(IDnumber.class4); return myData; } } return ""; } } } }

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  • DKIMPROXY signing wrong domain

    - by user64566
    Just.... wont sign a thing... The dkimproxy_out.conf: # specify what address/port DKIMproxy should listen on listen 127.0.0.1:10028 # specify what address/port DKIMproxy forwards mail to relay 127.0.0.1:10029 # specify what domains DKIMproxy can sign for (comma-separated, no spaces) domain tinymagnet.com,hypnoenterprises.com # specify what signatures to add signature dkim(c=relaxed) signature domainkeys(c=nofws) # specify location of the private key keyfile /etc/postfix/dkim/private.key # specify the selector (i.e. the name of the key record put in DNS) selector mail The direct connection straight to the server, making it clear that this is a problem with dkimproxy and not postfix... mmxbass@hypno1:~$ telnet localhost 10028 Trying 127.0.0.1... Connected to localhost.localdomain. Escape character is '^]'. 220 hypno1.hypnoenterprises.com ESMTP Postfix (Debian/GNU) EHLO hypno1.hypnoenterprises.com 250-hypno1.hypnoenterprises.com 250-PIPELINING 250-SIZE 250-ETRN 250-STARTTLS 250-AUTH PLAIN LOGIN 250-AUTH=PLAIN LOGIN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN MAIL FROM:<[email protected]> 250 2.1.0 Ok RCPT TO:<[email protected]> 250 2.1.5 Ok DATA 354 End data with <CR><LF>.<CR><LF> SUBJECT:test . 250 2.0.0 Ok: queued as B62A78D94F QUIT 221 2.0.0 Bye Now lets look at the mail headers as reported by myiptest.com: From [email protected] Thu Dec 23 18:57:14 2010 Return-path: Envelope-to: [email protected] Delivery-date: Thu, 23 Dec 2010 18:57:14 +0000 Received: from [184.82.95.154] (helo=hypno1.hypnoenterprises.com) by myiptest.com with esmtp (Exim 4.69) (envelope-from ) id 1PVqLi-0004YR-5f for [email protected]; Thu, 23 Dec 2010 18:57:14 +0000 Received: from hypno1.hypnoenterprises.com (localhost.localdomain [127.0.0.1]) by hypno1.hypnoenterprises.com (Postfix) with ESMTP id 878418D902 for ; Thu, 23 Dec 2010 13:57:26 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha1; c=simple; d=hypnoenterprises.com; h= from:to:subject:date:mime-version:content-type :content-transfer-encoding:message-id; s=mail; bh=uoq1oCgLlTqpdD X/iUbLy7J1Wic=; b=HxBKTGjzTpZSZU8xkICtARCKxqriqZK+qHkY1U8qQlOw+S S1wlZxzTeDGIOgeiTviGDpcKWkLLTMlUvx8dY4FuT8K1/raO9nMC7xjG2uLayPX0 zLzm4Srs44jlfRQIjrQd9tNnp35Wkry6dHPv1u21WUvnDWaKARzGGHRLfAzW4= Received: from localhost (localhost.localdomain [127.0.0.1]) by hypno1.hypnoenterprises.com (Postfix) with ESMTP id 2A04A8D945 for ; Thu, 23 Dec 2010 13:57:26 -0500 (EST) X-Virus-Scanned: Debian amavisd-new at hypno1.hypnoenterprises.com Received: from hypno1.hypnoenterprises.com ([127.0.0.1]) by localhost (hypno1.hypnoenterprises.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Ua7BnnzmIaUO for ; Thu, 23 Dec 2010 13:57:25 -0500 (EST) Received: from phoenix.localnet (c-76-23-245-211.hsd1.ma.comcast.net [76.23.245.211]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by hypno1.hypnoenterprises.com (Postfix) with ESMTPSA id 48A0D8D90D for ; Thu, 23 Dec 2010 13:57:25 -0500 (EST) From: Joshua Pech To: [email protected] Subject: test Date: Thu, 23 Dec 2010 13:57:25 -0500 User-Agent: KMail/1.13.5 (Linux/2.6.32-5-amd64; KDE/4.4.5; x86_64; ; ) MIME-Version: 1.0 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: DomainKey-Status: no signature Received-SPF: pass (myiptest.com: domain of tinymagnet.com designates 184.82.95.154 as permitted sender) Notice how the dkim signature specifies the d=hypnoenterprises.com.... why?

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  • Managing highly repetitive code and documentation in Java

    - by polygenelubricants
    Highly repetitive code is generally a bad thing, and there are design patterns that can help minimize this. However, sometimes it's simply inevitable due to the constraints of the language itself. Take the following example from java.util.Arrays: /** * Assigns the specified long value to each element of the specified * range of the specified array of longs. The range to be filled * extends from index <tt>fromIndex</tt>, inclusive, to index * <tt>toIndex</tt>, exclusive. (If <tt>fromIndex==toIndex</tt>, the * range to be filled is empty.) * * @param a the array to be filled * @param fromIndex the index of the first element (inclusive) to be * filled with the specified value * @param toIndex the index of the last element (exclusive) to be * filled with the specified value * @param val the value to be stored in all elements of the array * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt> * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or * <tt>toIndex &gt; a.length</tt> */ public static void fill(long[] a, int fromIndex, int toIndex, long val) { rangeCheck(a.length, fromIndex, toIndex); for (int i=fromIndex; i<toIndex; i++) a[i] = val; } The above snippet appears in the source code 8 times, with very little variation in the documentation/method signature but exactly the same method body, one for each of the root array types int[], short[], char[], byte[], boolean[], double[], float[], and Object[]. I believe that unless one resorts to reflection (which is an entirely different subject in itself), this repetition is inevitable. I understand that as a utility class, such high concentration of repetitive Java code is highly atypical, but even with the best practice, repetition does happen! Refactoring doesn't always work because it's not always possible (the obvious case is when the repetition is in the documentation). Obviously maintaining this source code is a nightmare. A slight typo in the documentation, or a minor bug in the implementation, is multiplied by however many repetitions was made. In fact, the best example happens to involve this exact class: Google Research Blog - Extra, Extra - Read All About It: Nearly All Binary Searches and Mergesorts are Broken (by Joshua Bloch, Software Engineer) The bug is a surprisingly subtle one, occurring in what many thought to be just a simple and straightforward algorithm. // int mid =(low + high) / 2; // the bug int mid = (low + high) >>> 1; // the fix The above line appears 11 times in the source code! So my questions are: How are these kinds of repetitive Java code/documentation handled in practice? How are they developed, maintained, and tested? Do you start with "the original", and make it as mature as possible, and then copy and paste as necessary and hope you didn't make a mistake? And if you did make a mistake in the original, then just fix it everywhere, unless you're comfortable with deleting the copies and repeating the whole replication process? And you apply this same process for the testing code as well? Would Java benefit from some sort of limited-use source code preprocessing for this kind of thing? Perhaps Sun has their own preprocessor to help write, maintain, document and test these kind of repetitive library code? A comment requested another example, so I pulled this one from Google Collections: com.google.common.base.Predicates lines 276-310 (AndPredicate) vs lines 312-346 (OrPredicate). The source for these two classes are identical, except for: AndPredicate vs OrPredicate (each appears 5 times in its class) "And(" vs Or(" (in the respective toString() methods) #and vs #or (in the @see Javadoc comments) true vs false (in apply; ! can be rewritten out of the expression) -1 /* all bits on */ vs 0 /* all bits off */ in hashCode() &= vs |= in hashCode()

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  • XSLT Select all nodes containing a specific substing

    - by Mike
    I'm trying to write an XPath that will select certain nodes that contain a specific word. In this case the word is, "Lockwood". The correct answer is 3. Both of these paths give me 3. count(//*[contains(./*,'Lockwood')]) count(BusinessLetter/*[contains(../*,'Lockwood')]) But when I try to output the text of each specific node //*[contains(./*,'Lockwood')][1] //*[contains(./*,'Lockwood')][2] //*[contains(./*,'Lockwood')][3] Node 1 ends up containing all the text and nodes 2 and 3 are blank. Can some one please tell me what's happening or what I'm doing wrong. Thanks. <?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="XPathFunctions.xsl"?> <BusinessLetter> <Head> <SendDate>November 29, 2005</SendDate> <Recipient> <Name Title="Mr."> <FirstName>Joshua</FirstName> <LastName>Lockwood</LastName> </Name> <Company>Lockwood &amp; Lockwood</Company> <Address> <Street>291 Broadway Ave.</Street> <City>New York</City> <State>NY</State> <Zip>10007</Zip> <Country>United States</Country> </Address> </Recipient> </Head> <Body> <List> <Heading>Along with this letter, I have enclosed the following items:</Heading> <ListItem>two original, execution copies of the Webucator Master Services Agreement</ListItem> <ListItem>two original, execution copies of the Webucator Premier Support for Developers Services Description between Lockwood &amp; Lockwood and Webucator, Inc.</ListItem> </List> <Para>Please sign and return all four original, execution copies to me at your earliest convenience. Upon receipt of the executed copies, we will immediately return a fully executed, original copy of both agreements to you.</Para> <Para>Please send all four original, execution copies to my attention as follows: <Person> <Name> <FirstName>Bill</FirstName> <LastName>Smith</LastName> </Name> <Address> <Company>Webucator, Inc.</Company> <Street>4933 Jamesville Rd.</Street> <City>Jamesville</City> <State>NY</State> <Zip>13078</Zip> <Country>USA</Country> </Address> </Person> </Para> <Para>If you have any questions, feel free to call me at <Phone>800-555-1000 x123</Phone> or e-mail me at <Email>[email protected]</Email>.</Para> </Body> <Foot> <Closing> <Name> <FirstName>Bill</FirstName> <LastName>Smith</LastName> </Name> <JobTitle>VP of Operations</JobTitle> </Closing> </Foot> </BusinessLetter>

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  • Why does one of two identical Javascripts work in Firefox?

    - by Gigpacknaxe
    Hi, I have two image swap functions and one works in Firefox and the other does not. The swap functions are identical and both work fine in IE. Firefox does not even recognize the images as hyperlinks. I am very confused and I hope some one can shed some light on this for me. Thank you very much in advance for any and all help. FYI: the working script swaps by onClick via DIV elements and the non-working script swaps onMouseOver/Out via "a" elements. Remember both of these work just fine in IE. Joshua Working Javascript in FF: <script type="text/javascript"> var aryImages = new Array(); aryImages[1] = "/tires/images/mich_prim_mxv4_profile.jpg"; aryImages[2] = "/tires/images/mich_prim_mxv4_tread.jpg"; aryImages[3] = "/tires/images/mich_prim_mxv4_side.jpg"; for (i=0; i < aryImages.length; i++) { var preload = new Image(); preload.src = aryImages[i]; } function swap(imgIndex, imgTarget) { document[imgTarget].src = aryImages[imgIndex]; } <div id="image-container"> <div style="text-align: right">Click small images below to view larger.</div> <div class="thumb-box" onclick="swap(1, 'imgColor')"><img src="/tires/images/thumbs/mich_prim_mxv4_profile_thumb.jpg" width="75" height="75" /></div> <div class="thumb-box" onclick="swap(2, 'imgColor')"><img src="/tires/images/thumbs/mich_prim_mxv4_tread_thumb.jpg" width="75" height="75" /></div> <div class="thumb-box" onclick="swap(3, 'imgColor')"><img src="/tires/images/thumbs/mich_prim_mxv4_side_thumb.jpg" width="75" height="75" /></div> <div><img alt="" name="imgColor" src="/tires/images/mich_prim_mxv4_profile.jpg" /></div> <div><a href="mich-prim-102-large.php"><img src="/tires/images/super_view.jpg" border="0" /></a></div> Not Working in FF: <script type="text/javascript"> var aryImages = new Array(); aryImages[1] = "/images/home-on.jpg"; aryImages[2] = "/images/home-off.jpg"; aryImages[3] = "/images/services-on.jpg"; aryImages[4] = "/images/services-off.jpg"; aryImages[5] = "/images/contact_us-on.jpg"; aryImages[6] = "/images/contact_us-off.jpg"; aryImages[7] = "/images/about_us-on.jpg"; aryImages[8] = "/images/about_us-off.jpg"; aryImages[9] = "/images/career-on.jpg"; aryImages[10] = "/images/career-off.jpg"; for (i=0; i < aryImages.length; i++) { var preload = new Image(); preload.src = aryImages[i]; } function swap(imgIndex, imgTarget) { document[imgTarget].src = aryImages[imgIndex]; } <td> <a href="home.php" onMouseOver="swap(1, 'home')" onMouseOut="swap(2, 'home')"><img name="home" src="/images/home-off.jpg" alt="Home Button" border="0px" /></a> </td>

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  • Looking Back at MIX10

    - by WeigeltRo
    It’s the sad truth of my life that even though I’m fascinated by airplanes and flight in general since my childhood days, my body doesn’t like flying. Even the ridiculously short flights inside Germany are taking their toll on me each time. Now combine this with sitting in the cramped space of economy class for many hours on a transatlantic flight from Germany to Las Vegas and back, and factor in some heavy dose of jet lag (especially on my way eastwards), and you get an idea why after coming back home I had this question on my mind: Was it really worth it to attend MIX10? This of course is a question that will also be asked by my boss at Comma Soft (for other reasons, obviously), who decided to send me and my colleague Jens Schaller, to the MIX10 conference. (A note to my German readers: An dieser Stelle der Hinweis, dass Comma Soft noch Silverlight-Entwickler und/oder UI-Designer für den Standort Bonn sucht – aussagekräftige Bewerbungen bitte an [email protected]) Too keep things short: My answer is yes. Before I’ll go into detail, let me ask the heretical questions whether tech conferences in general still make sense. There was a time, where actually being at a tech conference gave you a head-start in regard to learning about new technologies. Nowadays this is no longer true, where every bit of information and every detail is immediately twittered, blogged and whatevered to death. In the case of MIX10 you even can download the video-taped sessions shortly after. So: Does visiting a conference still make sense? It depends on what you expect from a conference. It should be clear to everybody that you’ll neither get exclusive information, nor receive training in a small group. What a conference does offer that sitting in front of your computer does not can be summarized as follows: Focus Being away from work and home will help you to focus on the presented information. Of course there are always the poor guys who are haunted by their work (with mails and short text messages reporting the latest showstopper problem), but in general being out of your office makes a huge difference. Inspiration With the focus comes the emotional involvement. I find it much easier to absorb information if I feel that certain vibe when sitting in a session. This still means that I have put work into reviewing the information later, but it’s a better starting point. And all the impressions collected at a (good) conference combined lead to a higher motivation – be it by the buzz (“this is gonna be sooo cool!”) or by the fear to fall behind (“man, we’ll have work on this, or else…”). People At a conference it’s pretty easy to get into contact with other people during breakfast, lunch and other breaks. This is a good opportunity to get a feel for what other development teams are doing (on a very general level of course, nobody will tell you about their secret formula) and what they are thinking about specific technologies. So MIX10 did offer focus, inspiration and people, but that would have meant nothing without valuable content. When I (being a frontend developer with a strong interest in UI/UX) planned my visit to MIX10, I made the decision to focus on the "soft" topics of design, interaction and user experience. I figured that I would be bombarded with all the technical details about Silverlight 4 anyway in the weeks and months to come. Actually, I would have liked to catch a few technical sessions, but the agenda wasn’t exactly in favor of people interested in any kind of Silverlight and UI/UX/Design topics. That’s one of my few complaints about the conference – I would have liked one more day and/or more sessions per day. Overall, the quality of the workshops and sessions was pretty high. In fact, looking back at my collection of conferences I’ve visited in the past I’d say that MIX10 ranks somewhere near the top spot. Here’s an overview of the workshops/sessions I attended (I’ll leave out the keynotes): Day 0 (Workshops on Sunday) Design Fundamentals for Developers Robby Ingebretsen is the man! Great workshop in three parts with the perfect mix of examples, well-structured definition of terminology and the right dose of humor. Robby was part of the WPF team before founding his own company so he not only has a strong interest in design (and the skillz!) but also the technical background.   Design Tools and Techniques Originally announced to be held by Arturo Toledo, the Rosso brothers from ArcheType filled in for the first two parts, and Corrina Black had a pretty general part about the Windows Phone UI. The first two thirds were a mixed bag; the two guys definitely knew what they were talking about, and the demos were great, but the talk lacked the preparation and polish of a truly great presentation. Corrina was not allowed to go into too much detail before the keynote on Monday, but the session was still very interesting as it showed how much thought went into the Windows Phone UI (and there’s always a lot to learn when people talk about their thought process). Day 1 (Monday) Designing Rich Experiences for Data-Centric Applications I wonder whether there was ever a test-run for this session, but what Ken Azuma and Yoshihiro Saito delivered in the first 15 minutes of a 30-minutes-session made me walk out. A commercial for a product (just great: a video showing a SharePoint plug-in in an all-Japanese UI) combined with the most generic blah blah one could imagine. EPIC FAIL.   Great User Experiences: Seamlessly Blending Technology & Design I switched to this session from the one above but I guess I missed the interesting part – what I did catch was what looked like a “look at the cool stuff we did” without being helpful. Or maybe I was just in a bad mood after the other session.   The Art, Technology and Science of Reading This talk by Kevin Larson was very interesting, but was more a presentation of what Microsoft is doing in research (pretty impressive) and in the end lacked a bit the helpful advice one could have hoped for.   10 Ways to Attack a Design Problem and Come Out Winning Robby Ingebretsen again, and again a great mix of theory and practice. The clean and simple, yet effective, UI of the reader app resulted in a simultaneous “wow” of Jens and me. If you’d watch only one session video, this should be it. Microsoft has to bring Robby back next year! Day 2 (Tuesday) Touch in Public: Multi-touch Interaction Design for Kiosks & Architectural Experiences Very interesting session by Jason Brush, a great inspiration with many details to look out for in the examples. Exactly what I was hoping for – and then some!   Designing Bing: Heart and Science How hard can it be to design the UI for a search engine? An input field and a list of results, that should be it, right? Well, not so fast! The talk by Paul Ray showed the many iterations to finally get it right (up to the choice of a specific blue for the links). And yes, I want an eye-tracking device to play around with!   The Elephant in the Room When Nishant Kothary presented a long list of what his session was not about, I told to myself (not having the description text present) “Am I in the wrong talk? Should I leave?”. Boy, was I wrong. A great talk about human factors in the process of designing stuff.   An Hour with Bill Buxton Having seen Bill Buxton’s presentation in the keynote, I just had to see this man again – even though I didn’t know what to expect. Being more or less unplanned and intended to be more of a conversation, the session didn’t provide a wealth of immediately useful information. Nevertheless Bill Buxton was impressive with his huge knowledge of seemingly everything. But this could/should have been a session some when in the evening and not in parallel to at least two other interesting talks. Day 3 (Wednesday) Design the Ordinary, Like the Fixie This session by DL Byron and Kevin Tamura started really well and brought across the message to keep things simple. But towards the end the talk lost some of its steam. And, as a member of the audience pointed out, they kind of ignored their own advice when they used a fancy presentation software other then PowerPoint that sometimes got in the way of showing things.   Developing Natural User Interfaces Speaking of alternative presentation software, Joshua Blake definitely had the most remarkable alternative to PowerPoint, a self-written program called NaturalShow that was controlled using multi-touch on a touch screen. Not a PowerPoint-killer, but impressive nevertheless. The (excellent) talk itself was kind of eye-opening in regard to what “multi-touch support” on various platforms (WPF, Silverlight, Windows Phone) actually means.   Treat your Content Right The talk by Tiffani Jones Brown wasn’t even on my planned schedule, but somehow I ended up in that session – and it was great. And even for people who don’t necessarily have to write content for websites, some points made by Tiffani are valid in many places, notably wherever you put texts with more than a single word into your UI. Creating Effective Info Viz in Microsoft Silverlight The last session of MIX10 I attended was kind of disappointing. At first things were very promising, with Matthias Shapiro giving a brief but well-structured introduction to info graphics and interactive visualizations. Then the live-coding began and while the result was interesting, too much time was spend on wrestling to get the code working. Ending earlier than planned, the talk was a bit light on actual content, but at least it included a nice list of resources. Conclusion It could be felt all across MIX10, UIs will take a huge leap forward; in fact, there are enough examples that have already. People who both have the technical know-how and at least a basic understanding of design (“literacy” as Bill Buxton called it) are in high demand. The concept of the MIX conference and initiatives like design.toolbox shows that Microsoft understands very well that frontend developers have to acquire new knowledge besides knowing how to hack code and putting buttons on a form. There are extremely exciting times before us, with lots of opportunity for those who are eager to develop their skills, that is for sure.

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers. Originally published on blogs.oracle.com/javaone.

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers.

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  • Implementation question involving implementing an interface

    - by Vivin Paliath
    I'm writing a set of collection classes for different types of Trees. I'm doing this as a learning exercise and I'm also hoping it turns out to be something useful. I really want to do this the right way and so I've been reading Effective Java and I've also been looking at the way Joshua Bloch implemented the collection classes by looking at the source. I seem to have a fair idea of what is being done, but I still have a few things to sort out. I have a Node<T> interface and an AbstractNode<T> class that implements the Node interface. I then created a GenericNode<T> (a node that can have 0 to n children, and that is part of an n-ary tree) class that extends AbstractNode<T> and implements Node<T>. This part was easy. Next, I created a Tree<T> interface and an AbstractTree<T> class that implements the Tree<T> interface. After that, I started writing a GenericTree<T> class that extends AbstractTree<T> and implements Tree<T>. This is where I started having problems. As far as the design is concerned, a GenericTree<T> can only consist of nodes of type GenericTreeNode<T>. This includes the root. In my Tree<T> interface I have: public interface Tree<T> { void setRoot(Node<T> root); Node<T> getRoot(); List<Node<T>> postOrder(); ... rest omitted ... } And, AbstractTree<T> implements this interface: public abstract class AbstractTree<T> implements Tree<T> { protected Node<T> root; protected AbstractTree() { } protected AbstractTree(Node<T> root) { this.root = root; } public void setRoot(Node<T> root) { this.root = root; } public Node<T> getRoot() { return this.root; } ... rest omitted ... } In GenericTree<T>, I can have: public GenericTree(Node<T> root) { super(root); } But what this means is that you can create a generic tree using any subtype of Node<T>. You can also set the root of a tree to any subtype of Node<T>. I want to be able to restrict the type of the node to the type of the tree that it can represent. To fix this, I can do this: public GenericTree(GenericNode<T> root) { super(root); } However, setRoot still accepts a parameter of type Node<T>. Which means a user can still create a tree with the wrong type of root node. How do I enforce this constraint? The only way I can think of doing is either: Do an instanceof which limits the check to runtime. I'm not a huge fan of this. Remove setRoot from the interface and have the base class implement this method. This means that it is not part of the contract and anyone who wants to make a new type of tree needs to remember to implement this method. Is there a better way? The second question I have concerns the return type of postOrder which is List<Node<T>>. This means that if a user is operating on a GenericTree<T> object and calls postOrder, he or she receives a list that consists of Node<T> objects. This means when iterating through (using a foreach construct) they would have perform an explicit cast to GenericNode<T> if they want to use methods that are only defined in that class. I don't like having to place this burden on the user. What are my options in this case? I can only think of removing the method from the interface and have the subclass implement this method making sure that it returns a list of appropriate subtype of Node<T>. However, this once again removes it from the contract and it's anyone who wants to create a new type of tree has to remember to implement this method. Is there a better way?

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  • Winform/Program and how to write class 1, class 2, class 3, class 4 in array to linklabels?!!?

    - by JB
    So my program works like this: using winforms, user enters ID number, using an array, based on the right id number, that student information and class schedule outputs in a message box! My question is how to take the 4 classes in the message box/array and write them to the linklabel text in form 2???? My Getschedule class contains the array and is listed below: namespace Eagle_Eye_Class_Finder { public class GetSchedule { IDnumber[] IDnumbers = new IDnumber[3]; public string GetDataFromNumber(string ID) { foreach (IDnumber IDCandidateMatch in IDnumbers) { if (IDCandidateMatch.ID == ID) { StringBuilder myData = new StringBuilder(); myData.AppendLine(IDCandidateMatch.Name); myData.AppendLine(": "); myData.AppendLine(IDCandidateMatch.ID); myData.AppendLine(IDCandidateMatch.year); myData.AppendLine(IDCandidateMatch.class1); myData.AppendLine(IDCandidateMatch.class2); myData.AppendLine(IDCandidateMatch.class3); myData.AppendLine(IDCandidateMatch.class4); //return myData; return myData.ToString(); } } return ""; } public GetSchedule() { IDnumbers[0] = new IDnumber() { Name = "Joshua Banks", ID = "900456317", year = "Senior", class1 = "TEET 4090", class2 = "TEET 3020", class3 = "TEET 3090", class4 = "TEET 4290" }; IDnumbers[1] = new IDnumber() { Name = "Sean Ward", ID = "900456318", year = "Junior", class1 = "ENGNR 4090", class2 = "ENGNR 3020", class3 = "ENGNR 3090", class4 = "ENGNR 4290" }; IDnumbers[2] = new IDnumber() { Name = "Terrell Johnson", ID = "900456319", year = "Sophomore", class1 = "BUS 4090", class2 = "BUS 3020", class3 = "BUS 3090", class4 = "BUS 4290" }; } public class IDnumber { public string Name { get; set; } public string ID { get; set; } public string year { get; set; } public string class1 { get; set; } public string class2 { get; set; } public string class3 { get; set; } public string class4 { get; set; } public static void ProcessNumber(IDnumber myNum) { StringBuilder myData = new StringBuilder(); myData.AppendLine(myNum.Name); myData.AppendLine(": "); myData.AppendLine(myNum.ID); myData.AppendLine(myNum.year); myData.AppendLine(myNum.class1); myData.AppendLine(myNum.class2); myData.AppendLine(myNum.class3); myData.AppendLine(myNum.class4); MessageBox.Show(myData.ToString()); } } } } My form 2 which will contain the linklabels is listed below: public class YOURCLASSSCHEDULE : System.Windows.Forms.Form { public System.Windows.Forms.LinkLabel linkLabel1; public System.Windows.Forms.LinkLabel linkLabel2; public System.Windows.Forms.LinkLabel linkLabel3; public System.Windows.Forms.LinkLabel linkLabel4; private Button button1; /// Required designer variable. public System.ComponentModel.Container components = null; public YOURCLASSSCHEDULE() { // InitializeComponent(); // TODO: Add any constructor code after InitializeComponent call } /// Clean up any resources being used. protected override void Dispose(bool disposing) { if (disposing) { if (components != null) { components.Dispose(); } } base.Dispose(disposing); } #region Windows Form Designer generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(YOURCLASSSCHEDULE)); this.linkLabel1 = new System.Windows.Forms.LinkLabel(); this.linkLabel2 = new System.Windows.Forms.LinkLabel(); this.linkLabel3 = new System.Windows.Forms.LinkLabel(); this.linkLabel4 = new System.Windows.Forms.LinkLabel(); this.button1 = new System.Windows.Forms.Button(); this.SuspendLayout(); // // linkLabel1 // this.linkLabel1.BackColor = System.Drawing.SystemColors.ActiveCaption; this.linkLabel1.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; this.linkLabel1.Font = new System.Drawing.Font("Times New Roman", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.linkLabel1.LinkArea = new System.Windows.Forms.LinkArea(0, 7); this.linkLabel1.LinkBehavior = System.Windows.Forms.LinkBehavior.HoverUnderline; this.linkLabel1.Location = new System.Drawing.Point(41, 123); this.linkLabel1.Name = "linkLabel1"; this.linkLabel1.Size = new System.Drawing.Size(288, 32); this.linkLabel1.TabIndex = 1; this.linkLabel1.TabStop = true; this.linkLabel1.Text = "Class 1"; this.linkLabel1.TextAlign = System.Drawing.ContentAlignment.MiddleCenter; this.linkLabel1.LinkClicked += new System.Windows.Forms.LinkLabelLinkClickedEventHandler(this.linkLabel1_LinkClicked); // // linkLabel2 // this.linkLabel2.BackColor = System.Drawing.SystemColors.ActiveCaption; this.linkLabel2.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; this.linkLabel2.Font = new System.Drawing.Font("Times New Roman", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.linkLabel2.LinkBehavior = System.Windows.Forms.LinkBehavior.HoverUnderline; this.linkLabel2.Location = new System.Drawing.Point(467, 123); this.linkLabel2.Name = "linkLabel2"; this.linkLabel2.Size = new System.Drawing.Size(288, 32); this.linkLabel2.TabIndex = 2; this.linkLabel2.TabStop = true; this.linkLabel2.Text = "Class 2"; this.linkLabel2.TextAlign = System.Drawing.ContentAlignment.MiddleCenter; this.linkLabel2.VisitedLinkColor = System.Drawing.Color.Navy; this.linkLabel2.LinkClicked += new System.Windows.Forms.LinkLabelLinkClickedEventHandler(this.linkLabel2_LinkClicked); // // linkLabel3 // this.linkLabel3.BackColor = System.Drawing.SystemColors.ActiveCaption; this.linkLabel3.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; this.linkLabel3.Font = new System.Drawing.Font("Times New Roman", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.linkLabel3.LinkBehavior = System.Windows.Forms.LinkBehavior.HoverUnderline; this.linkLabel3.Location = new System.Drawing.Point(41, 311); this.linkLabel3.Name = "linkLabel3"; this.linkLabel3.Size = new System.Drawing.Size(288, 32); this.linkLabel3.TabIndex = 3; this.linkLabel3.TabStop = true; this.linkLabel3.Text = "Class 3"; this.linkLabel3.TextAlign = System.Drawing.ContentAlignment.MiddleCenter; this.linkLabel3.LinkClicked += new System.Windows.Forms.LinkLabelLinkClickedEventHandler(this.linkLabel3_LinkClicked); // // linkLabel4 // this.linkLabel4.BackColor = System.Drawing.SystemColors.ActiveCaption; this.linkLabel4.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; this.linkLabel4.Font = new System.Drawing.Font("Times New Roman", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.linkLabel4.LinkBehavior = System.Windows.Forms.LinkBehavior.HoverUnderline; this.linkLabel4.Location = new System.Drawing.Point(467, 311); this.linkLabel4.Name = "linkLabel4"; this.linkLabel4.Size = new System.Drawing.Size(288, 32); this.linkLabel4.TabIndex = 4; this.linkLabel4.TabStop = true; this.linkLabel4.Text = "Class 4"; this.linkLabel4.TextAlign = System.Drawing.ContentAlignment.MiddleCenter; this.linkLabel4.LinkClicked += new System.Windows.Forms.LinkLabelLinkClickedEventHandler(this.linkLabel4_LinkClicked); // // this.AutoScaleBaseSize = new System.Drawing.Size(6, 15); this.BackgroundImage = ((System.Drawing.Image)(resources.GetObject("$this.BackgroundImage"))); this.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Stretch; this.ClientSize = new System.Drawing.Size(790, 482); this.Controls.Add(this.button1); this.Controls.Add(this.linkLabel4); this.Controls.Add(this.linkLabel3); this.Controls.Add(this.linkLabel2); this.Controls.Add(this.linkLabel1); this.Font = new System.Drawing.Font("OldDreadfulNo7 BT", 8.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0))); this.Name = "YOURCLASSSCHEDULE"; this.Text = "Your Classes"; this.Load += new System.EventHandler(this.Form2_Load); this.ResumeLayout(false); } #endregion public void Form2_Load(object sender, System.EventArgs e) { // if (text == "900456317") // { //} } public void linkLabel1_LinkClicked(object sender, System.Windows.Forms.LinkLabelLinkClickedEventArgs e) { System.Diagnostics.Process.Start("http://www.georgiasouthern.edu/map/"); } private void linkLabel2_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e) { } private void linkLabel3_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e) { } private void linkLabel4_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e) { } private void button1_Click(object sender, EventArgs e) { Form1 form1 = new Form1(); form1.Show(); this.Hide(); } } }

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