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  • Do you use logical negation operator (!) in "if" statement or check on "== false"

    - by Taras Terebkov
    Hello everyone, I just want to conduct a little survey about code style developers prefer. For me there are two ways to write "if" in such languages as Java, C#, C++, etc. (1) Logical negation operator public void foo() { if (!SessionManager.getInstance().hasActiveSession()) { . . . . . } } (2) Check on "false" public void foo() { if (SessionManager.getInstance().hasActiveSession() == false) { . . . . . } } I always believe that first way is much worst then the second one. Cause usually you don't "read" the code, but "recognize" it in one brief look. And exclamation symbol slipped from your mind, just disturbing you somewhere on the bottom of your unconscious. And only during reading the "if" block below you understand, that the logic is opposite - no sessions in "if" On the other hand in the second way of writing, an eye immediately catches words "SessionManager", "hasActiveSession" and "false". Also for me, the situation with "true" is different. In code like class SessionManager { private bool hasSession; public void foo() { if (hasSession == true) { . . . . . } else { . . . . . } } } I find "true" superfluous. why we repeating the sentence two times? The following is shorter and quicker to catch. class SessionManager { private bool hasSession; public void foo() { if (hasSession) { . . . . . } else { . . . . . } } } What do YOU think, guys?

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  • Save/Load jFreechart TimeSeriesCollection chart from XML

    - by IMAnis_tn
    I'm working with this exemple wich put rondom dynamic data into a TimeSeriesCollection chart. My problem is that i can't find how to : 1- Make a track of the old data (of the last hour) when they pass the left boundary (because the data point move from the right to the left ) of the view area just by implementing a horizontal scroll bar. 2- Is XML a good choice to save my data into when i want to have all the history of the data? public class DynamicDataDemo extends ApplicationFrame { /** The time series data. */ private TimeSeries series; /** The most recent value added. */ private double lastValue = 100.0; public DynamicDataDemo(final String title) { super(title); this.series = new TimeSeries("Random Data", Millisecond.class); final TimeSeriesCollection dataset = new TimeSeriesCollection(this.series); final JFreeChart chart = createChart(dataset); final ChartPanel chartPanel = new ChartPanel(chart); final JPanel content = new JPanel(new BorderLayout()); content.add(chartPanel); chartPanel.setPreferredSize(new java.awt.Dimension(500, 270)); setContentPane(content); } private JFreeChart createChart(final XYDataset dataset) { final JFreeChart result = ChartFactory.createTimeSeriesChart( "Dynamic Data Demo", "Time", "Value", dataset, true, true, false ); final XYPlot plot = result.getXYPlot(); ValueAxis axis = plot.getDomainAxis(); axis.setAutoRange(true); axis.setFixedAutoRange(60000.0); // 60 seconds axis = plot.getRangeAxis(); axis.setRange(0.0, 200.0); return result; } public void go() { final double factor = 0.90 + 0.2 * Math.random(); this.lastValue = this.lastValue * factor; final Millisecond now = new Millisecond(); System.out.println("Now = " + now.toString()); this.series.add(new Millisecond(), this.lastValue); } public static void main(final String[] args) throws InterruptedException { final DynamicDataDemo demo = new DynamicDataDemo("Dynamic Data Demo"); demo.pack(); RefineryUtilities.centerFrameOnScreen(demo); demo.setVisible(true); while(true){ demo.go(); Thread.currentThread().sleep(1000); } } }

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  • Another Spring + Hibernate + JPA question

    - by Albinoswordfish
    I'm still struggling with changing my Spring Application to use Hibernate with JPA to do database activities. Well apparently from a previous post I need an persistence.xml file. However do I need to make changes to my current DAO class? public class JdbcProductDao extends Dao implements ProductDao { /** Logger for this class and subclasses */ protected final Log logger = LogFactory.getLog(getClass()); public List<Product> getProductList() { logger.info("Getting products!"); List<Product> products = getSimpleJdbcTemplate().query( "select id, description, price from products", new ProductMapper()); return products; } public void saveProduct(Product prod) { logger.info("Saving product: " + prod.getDescription()); int count = getSimpleJdbcTemplate().update( "update products set description = :description, price = :price where id = :id", new MapSqlParameterSource().addValue("description", prod.getDescription()) .addValue("price", prod.getPrice()) .addValue("id", prod.getId())); logger.info("Rows affected: " + count); } private static class ProductMapper implements ParameterizedRowMapper<Product> { public Product mapRow(ResultSet rs, int rowNum) throws SQLException { Product prod = new Product(); prod.setId(rs.getInt("id")); prod.setDescription(rs.getString("description")); prod.setPrice(new Double(rs.getDouble("price"))); return prod; } } } Also my Product.Java is below public class Product implements Serializable { private int id; private String description; private Double price; public void setId(int i) { id = i; } public int getId() { return id; } public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } public Double getPrice() { return price; } public void setPrice(Double price) { this.price = price; } public String toString() { StringBuffer buffer = new StringBuffer(); buffer.append("Description: " + description + ";"); buffer.append("Price: " + price); return buffer.toString(); } } I guess my question would be, How would my current classes change after using Hibernate + JPA with an Entity Manager

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  • I am unsure of how to access a persistence entity from a JSP page?

    - by pharma_joe
    Hi, I am just learning Java EE, I have created a Persistence entity for a User object, which is stored in the database. I am now trying to create a JSP page that will allow a client to enter a new User object into the System. I am unsure of how the JSP page interacts with the User facade, the tutorials are confusing me a little. This is the code for the facade: <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Add User to System</title> </head> <body> <h2>Add User</h2> <h3>Please fill out the details to add a user to the system</h3> <form action=""> <label>Email:</label> <input type="text" name="email"><br /> <label>Password:</label> <input type="password" name="name"><br /> <label>Name:</label> <input type="text" name="name"><br /> <label>Address:</label> <input type="text" name="address"><br /> <label>Type:</label> <select name="type"> <option>Administrator</option> <option>Member</option> </select><br /> <input type="submit" value="Add" name="add"/> <input type="reset" value="clear" /> </form> </body> This is the code I have to add a new User object within the User facade class: @Stateless public class CinemaUserFacade { @PersistenceContext(unitName = "MonashCinema-warPU") private EntityManager em; public void create(CinemaUser cinemaUser) { em.persist(cinemaUser); } I am finding it a little difficult to get my head around the whole MVC thing, getting there but would appreciate it if someone could turn the light on for me!

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  • How can a button click method find out which item is selected in a ListView?

    - by Ian Bayley
    I have a single screen with a bank of buttons below a ListView. Entries on the ListView light up in orange when I scroll so I assume that are selected. When I then press the "Delete" button I want the onClickListener to remove the currently selected entry. But getSelectedItemPosition() always gives me -1. If I can't hope to use the GUI controls in this way, please give me another way of getting the same result. I have even tried setting the onClickListener of the List View to store the index before the button is pressed (in case pressing the button unselects the entry) but even that is always -1 it seems. Here's the code (without the modification which didn't work) package com.bayley; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.EditText; import android.widget.ListView; import java.util.ArrayList; /** * * @author p0074564 */ public class September extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.main); final ListView myListView = (ListView) findViewById(R.id.myListView); Button addButton = (Button) findViewById(R.id.AddButton); Button deleteButton = (Button) findViewById(R.id.DeleteButton); final EditText editText = (EditText) findViewById(R.id.myEditText); final ArrayList<String> todoItems = new ArrayList<String>(); todoItems.add("Monday"); todoItems.add("Tuesday"); todoItems.add("Wednesday"); final ArrayAdapter<String> aa = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, todoItems); myListView.setAdapter(aa); addButton.setOnClickListener(new Button.OnClickListener() { public void onClick(View v) { todoItems.add(editText.getText().toString()); aa.notifyDataSetChanged(); } }); deleteButton.setOnClickListener(new Button.OnClickListener() { public void onClick(View v) { // always returns -1 unfortunately ie nothing is ever selected int index = myListView.getSelectedItemPosition(); if (index >= 0) { todoItems.remove(index); } aa.notifyDataSetChanged(); } }); } }

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  • JList with JScrollPane and prototype cell value wraps element names (replaces with dots instead of s

    - by Tom
    I've got a Jlist inside a JScrollPane and I've set a prototype value so that it doesn't have to calculate the width for big lists, but just uses this default width. Now, the problem is that the Jlist is for some reason replacing the end of an element with dots (...) so that a horizontal scrollbar will never be shown. How do I disable with "wrapping"? So that long elements are not being replaced with dots if they are wider than the Jlist's width? I've reproduced the issue in a small example application. Please run it if you don't understand what I mean: import javax.swing.*; import java.awt.*; public class Test { //window private static final int windowWidth = 450; private static final int windowHeight = 500; //components private JFrame frame; private JList classesList; private DefaultListModel classesListModel; public Test() { load(); } private void load() { //create window frame = new JFrame("Test"); frame.setSize(windowWidth, windowHeight); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setUndecorated(true); frame.getRootPane().setWindowDecorationStyle(JRootPane.PLAIN_DIALOG); //classes list classesListModel = new DefaultListModel(); classesList = new JList(classesListModel); classesList.setPrototypeCellValue("prototype value"); classesList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); classesList.setVisibleRowCount(20); JScrollPane scrollClasses = new JScrollPane(classesList, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED); for (int i = 0; i < 200; i++) { classesListModel.addElement("this is a long string, does not fit in width"); } //panel JPanel drawingArea = new JPanel(); drawingArea.setBackground(Color.white); drawingArea.add(scrollClasses); frame.add(drawingArea); //set visible frame.setVisible(true); } } Even if you force horizontal scrollbar, you still won't be able to scroll because the element is actually not wider than the width because of the dot (...) wrapping. Thanks in advance.

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  • How can i access or execute .java file in another javafile in android app development?

    - by Srikanth Naidu
    i got 2 java files app.java and gallaery.java App.java public class App extends Activity implements OnClickListener { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Button Listvideo = (Button) findViewById(R.id.Listvideo); Listvideo.setOnClickListener(this); public void onClick(View view) { if (view == findViewById(R.id.Listvideo)) { // i have to call gallery.java here which executes list of images in the android pone } }

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  • How can I store large amount of data from a database to XML (speed problem, part three)?

    - by Andrija
    After getting some responses, the current situation is that I'm using this tip: http://www.ibm.com/developerworks/xml/library/x-tipbigdoc5.html (Listing 1. Turning ResultSets into XML), and XMLWriter for Java from http://www.megginson.com/downloads/ . Basically, it reads date from the database and writes them to a file as characters, using column names to create opening and closing tags. While doing so, I need to make two changes to the input stream, namely to the dates and numbers. // Iterate over the set while (rs.next()) { w.startElement("row"); for (int i = 0; i < count; i++) { Object ob = rs.getObject(i + 1); if (rs.wasNull()) { ob = null; } String colName = meta.getColumnLabel(i + 1); if (ob != null ) { if (ob instanceof Timestamp) { w.dataElement(colName, Util.formatDate((Timestamp)ob, dateFormat)); } else if (ob instanceof BigDecimal){ w.dataElement(colName, Util.transformToHTML(new Integer(((BigDecimal)ob).intValue()))); } else { w.dataElement(colName, ob.toString()); } } else { w.emptyElement(colName); } } w.endElement("row"); } The SQL that gets the results has the to_number command (e.g. to_number(sif.ID) ID ) and the to_date command (e.g. TO_DATE (sif.datum_do, 'DD.MM.RRRR') datum_do). The problems are that the returning date is a timestamp, meaning I don't get 14.02.2010 but rather 14.02.2010 00:00:000 so I have to format it to the dd.mm.yyyy format. The second problem are the numbers; for some reason, they are in database as varchar2 and can have leading zeroes that need to be stripped; I'm guessing I could do that in my SQL with the trim function so the Util.transformToHTML is unnecessary (for clarification, here's the method): public static String transformToHTML(Integer number) { String result = ""; try { result = number.toString(); } catch (Exception e) {} return result; } What I'd like to know is a) Can I get the date in the format I want and skip additional processing thus shortening the processing time? b) Is there a better way to do this? We're talking about XML files that are in the 50 MB - 250 MB filesize category.

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  • driver.findElement() with iframe and elements without ID

    - by user1864657
    Java Code: driver.switchTo().frame(0); WebElement elemText = driver.findElement(By.xpath("/html/body[contains(@class='forum')]")); //WebElement elemText = driver.findElement(By.xpath("//td[@id='cke_contents_vB_Editor_001_editor']/textarea")); elemText.sendKeys(message); elemText.submit(); forumLink = driver.getCurrentUrl(); HTML Code: <td id="cke_contents_vB_Editor_001_editor" class="cke_contents" style="height:1726px" role="presentation"> <iframe style="width:100%;height:100%" frameborder="0" title="Rich text editor, vB_Editor_001_editor, press ALT 0 for help." src="" tabindex="-1" allowtransparency="true"> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html dir="ltr" lang="en" contenteditable="true"> <head> <title data-cke-title="Rich text editor, vB_Editor_001_editor, press ALT 0 for help.">Rich text editor, vB_Editor_001_editor, press ALT 0 for help.</title> <base href="http://fairplay.garena.com/" data-cke-temp="1"> <link type="text/css" rel="stylesheet" href="http://fairplay.garena.com/clientscript/vbulletin_css/style00008l/editor_contents.css"> <style type="text/css" data-cke-temp="1"> form{border: 1px dotted #FF0000;padding: 2px;} img.cke_hidden{background-image: url(http://fairplay.garena.com/clientscript/ckeditor/plugins/forms/images/hiddenfield.gif?t=B37D54V);background-position: center center;background-repeat: no-repeat;border: 1px solid #a9a9a9;width: 16px !important;height: 16px !important;} img.cke_iframe{background-image: url(http://fairplay.garena.com/clientscript/ckeditor/plugins/iframe/images/placeholder.png?t=B37D54V);background-position: center center;background-repeat: no-repeat;border: 1px solid #a9a9a9;width: 80px;height: 80px;} img.cke_anchor{background-image: url(http://fairplay.garena.com/clientscript/ckeplugins/vblink/images/anchor.gif?t=B37D54V);background-position: center center;background-repeat: no-repeat;border: 1px solid #a9a9a9;width: 18px !important;height: 18px !important;} a.cke_anchor{background-image: url(http://fairplay.garena.com/clientscript/ckeplugins/vblink/images/anchor.gif?t=B37D54V);background-position: left center;background-repeat: no-repeat;border: 1px solid #a9a9a9;padding-left: 18px;} </style> </head> <body class="forum" spellcheck="true"> </body> </html> </iframe> </td> Image: http://s9.postimage.org/nwyvq3san/Screen_Shot038.jpg I can't find a way to get elements inside a iframe and without id. Can you help me?

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  • Which work process in my company should I Improve first?

    - by shoren
    I've just started to work in a new place, and I see several things they do that I find really terrible, and I want to know if they are indeed so wrong, or I am just too strict. Please let me know if my criticism is in place, and your opinion on which problem is the worst and should be fixed first. The developement is all in Java. 1) Not using svnignore. This means svn stat can't be used, and developers forget to add files and break the build. 2) Generated files go to same folders as committed files. Can't use simple maven clean, have to find them one by one. Maven clean doesn't remove all of them. 3) Not fixing IDE analyze warnings. Analyze code returns about 5,000 warning, of many different kinds. 4) Not following conventions: spring beans names sometimes start with uppercase and sometimes not, ant properties sometimes with underline and sometimes with dots delimiter, etc. 5) Incremental build takes 6 minutes, even when nothing is changed. 6) Developers only use remote debug, and don't know how to run the Tomcat server internally from the IDE. 7) Developers always restart the server after every compilation, instead of dynamically reloading the class and saving the server's state. It takes them at least 10 minutes to start checking any change in the code. 8) Developers only compile from command line. When there are compilation errors, they manually open the file and go the the problematic line. 9) A complete mess in project dependencies. Over 200 open sources are depended on, and no one knows what is indeed needed and why. They do know that not all dependencies are necessary. 10) Mixing Maven and Ant in a way that disables the benefits of both. In one case, even dependency checks are not done by Maven. 11) Not using generics properly. 12) Developers don't use Subversion integration with IDE (Eclipse, Intellij Idea). What do you think? Where should I start? Is any of the things I mentioned not really a problem?

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  • Hot to get rid of memory allocations/deallocations in swig wrappers?

    - by Dmitriy Matveev
    I want to use swig for generation of read-only wrappers for a complex object. The object which I want to wrap will always be existent while I will read it. And also I will only use my wrappers at the time that object is existent, thus I don't need any memory management from SWIG. For following swig interface: %module test %immutable; %inline %{ struct Foo { int a; }; struct Bar { int b; Foo f; }; %} I will have a wrappers which will have a lot of garbage in generated interfaces and do useless work which will reduce performance in my case. Generated java wrapper for Bar class will be like this: public class Bar { private long swigCPtr; protected boolean swigCMemOwn; protected Bar(long cPtr, boolean cMemoryOwn) { swigCMemOwn = cMemoryOwn; swigCPtr = cPtr; } protected static long getCPtr(Bar obj) { return (obj == null) ? 0 : obj.swigCPtr; } protected void finalize() { delete(); } public synchronized void delete() { if (swigCPtr != 0) { if (swigCMemOwn) { swigCMemOwn = false; testJNI.delete_Bar(swigCPtr); } swigCPtr = 0; } } public int getB() { return testJNI.Bar_b_get(swigCPtr, this); } public Foo getF() { return new Foo(testJNI.Bar_f_get(swigCPtr, this), true); } public Bar() { this(testJNI.new_Bar(), true); } } I don't need 'swigCMemOwn' field in my wrapper since it always will be false. All code related to this field will also be useless. There are also unnecessary logic in native code: SWIGEXPORT jlong JNICALL Java_some_testJNI_Bar_1f_1get(JNIEnv *jenv, jclass jcls, jlong jarg1, jobject jarg1_) { jlong jresult = 0 ; struct Bar *arg1 = (struct Bar *) 0 ; Foo result; (void)jenv; (void)jcls; (void)jarg1_; arg1 = *(struct Bar **)&jarg1; result = ((arg1)->f); { Foo * resultptr = (Foo *) malloc(sizeof(Foo)); memmove(resultptr, &result, sizeof(Foo)); *(Foo **)&jresult = resultptr; } return jresult; } I don't need these calls to malloc and memmove. I want to force swig to resolve both of these problems, but don't know how. Is it possible?

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  • How to update a TextView on ButtonClick with Spinner(s) values

    - by source.rar
    Hi, I am trying to populate a TextView based on the current selected options in 3 Spinner(s) but cant seem to figure out how to retrieve the selected values from the Spinners to invoke the update function with. Here is my current code (quite messy but I'm just learning Java :)), public class AgeFun extends Activity { private String[] dayNames; private String[] yearArray; private final static int START_YEAR = 1990; private static TextView textDisp; private Button calcButton; private static Spinner spinnerDay, spinnerYear, spinnerMonth; private static ArrayAdapter<?> monthAdapter, dayAdapter, yearAdapter; private int year, month, day; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); year = 2000; month = 1; day = 1; textDisp = (TextView) findViewById(R.id.textView1); calcButton = (Button) findViewById(R.id.button); calcButton.setOnClickListener(new OnClickListener() { public void onClick(View v) { // Perform action on clicks AgeFun.updateAge(year, month, day); } }); // Month spinner spinnerMonth = (Spinner) findViewById(R.id.spinnerFirst); monthAdapter = ArrayAdapter.createFromResource( this, R.array.monthList, android.R.layout.simple_spinner_item); monthAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); spinnerMonth.setAdapter(monthAdapter); // Day spinner dayNames = new String[31]; for(int i =1; i <= 31; ++i) { dayNames[i-1] = Integer.toString(i); } spinnerDay = (Spinner) findViewById(R.id.spinnerSecond); dayAdapter = new ArrayAdapter<CharSequence>(this, android.R.layout.simple_spinner_item, dayNames); spinnerDay.setAdapter(dayAdapter); // Year spinner yearArray = new String[40]; for(int i =0; i < 40; ++i) { yearArray[i] = Integer.toString(START_YEAR+i); } spinnerYear = (Spinner) findViewById(R.id.spinnerThird); yearAdapter = new ArrayAdapter<CharSequence>(this, android.R.layout.simple_spinner_item, yearArray); spinnerYear.setAdapter(yearAdapter); updateAge(2000,1,1); } private static void updateAge(int year, int month, int day) { Date dob = new GregorianCalendar(year, month, day).getTime(); Date currDate = new Date(); long age = (currDate.getTime() - dob.getTime()) / (1000 * 60 * 60 * 24) / 365; textDisp.setText("Your are " + Long.toString(age) + " years old"); } } Any help with this would be great. TIA

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  • Why does JAXB not create a member variable in its generated code when an XML schema base type and subtype have the same element declared in them?

    - by belltower
    I have a question regarding with regard to JAXB generated classes. As you can I see, I have a complex type, DG_PaymentIdentification1, declared in my schema. Its a restriction of PaymentIdentification1. DG_PaymentIdentification1 is also identical to PaymentIdentification1. I also have a type called DG_CreditTransferTransactionInformation10 which has a base type of CreditTransferTransactionInformation10 and is identical to it. I have included the relevant XML schema snippets below. <xs:complexType name="DG_PaymentIdentification1"> <xs:complexContent> <xs:restriction base="PaymentIdentification1"> <xs:sequence> <xs:element name="InstrId" type="DG_Max35Text_REF" minOccurs="0"/> <xs:element name="EndToEndId" type="DG_Max35Text_REF" id="DG-41"/> </xs:sequence> </xs:restriction> </xs:complexContent> </xs:complexType> <xs:complexType name="PaymentIdentification1"> <xs:sequence> <xs:element name="InstrId" type="Max35Text" minOccurs="0"/> <xs:element name="EndToEndId" type="Max35Text"/> </xs:sequence> </xs:complexType> <xs:complexType name="DG_CreditTransferTransactionInformation10"> <xs:complexContent> <xs:restriction base="CreditTransferTransactionInformation10"> <xs:sequence> <xs:element name="PmtId" type="DG_PaymentIdentification1"/> <xs:simpleType name="DG_Max35Text_REF"> <xs:restriction base="DG_NotEmpty35"> <xs:pattern value="[\-A-Za-z0-9\+/\?:\(\)\.,'&#x20;]*"/> </xs:restriction> </xs:simpleType> <xs:simpleType name="Max35Text"> <xs:restriction base="xs:string"> <xs:minLength value="1"/> <xs:maxLength value="35"/> </xs:restriction> </xs:simpleType> JAXB generates the following java class for DG_PaymentIdentification1: @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "DG_CreditTransferTransactionInformDGion10") public class DGCreditTransferTransactionInformation10 extends CreditTransferTransactionInformation10 { } My question is why doesnt the DGCreditTransferTransactionInformation10 generated class have a variable of type DG_PaymentIdentification1 in the generated code? The base class CreditTransferTransactionInformation10 does have a type PaymentIdentification1 declared in it. Is there any way of ensuring that DGCreditTransferTransactionInformation10 will have a DG_PaymentIdentification1 in it?

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  • I need to modify a program to use arrays and a method call. Should I modify the running file, the data collection file, or both?

    - by g3n3rallyl0st
    I have to have multiple classes for this program. The problem is, I don't fully understand arrays and how they work, so I'm a little lost. I will post my program I have written thus far so you can see what I'm working with, but I don't expect anyone to DO my assignment for me. I just need to know where to start and I'll try to go from there. I think I need to use a double array since I will be working with decimals since it deals with money, and my method call needs to calculate total price for all items entered by the user. Please help: RUNNING FILE package inventory2; import java.util.Scanner; public class RunApp { public static void main(String[] args) { Scanner input = new Scanner( System.in ); DataCollection theProduct = new DataCollection(); String Name = ""; double pNumber = 0.0; double Units = 0.0; double Price = 0.0; while(true) { System.out.print("Enter Product Name: "); Name = input.next(); theProduct.setName(Name); if (Name.equalsIgnoreCase("stop")) { return; } System.out.print("Enter Product Number: "); pNumber = input.nextDouble(); theProduct.setpNumber(pNumber); System.out.print("Enter How Many Units in Stock: "); Units = input.nextDouble(); theProduct.setUnits(Units); System.out.print("Enter Price Per Unit: "); Price = input.nextDouble(); theProduct.setPrice(Price); System.out.print("\n Product Name: " + theProduct.getName()); System.out.print("\n Product Number: " + theProduct.getpNumber()); System.out.print("\n Amount of Units in Stock: " + theProduct.getUnits()); System.out.print("\n Price per Unit: " + theProduct.getPrice() + "\n\n"); System.out.printf("\n Total cost for %s in stock: $%.2f\n\n\n", theProduct.getName(), theProduct.calculatePrice()); } } } DATA COLLECTION FILE package inventory2; public class DataCollection { String productName; double productNumber, unitsInStock, unitPrice, totalPrice; public DataCollection() { productName = ""; productNumber = 0.0; unitsInStock = 0.0; unitPrice = 0.0; } //setter methods public void setName(String name) { productName = name; } public void setpNumber(double pNumber) { productNumber = pNumber; } public void setUnits(double units) { unitsInStock = units; } public void setPrice(double price) { unitPrice = price; } //getter methods public String getName() { return productName; } public double getpNumber() { return productNumber; } public double getUnits() { return unitsInStock; } public double getPrice() { return unitPrice; } public double calculatePrice() { return (unitsInStock * unitPrice); } }

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  • Illegal Start of Expression

    - by Kraivyne
    Hello there, I have just started to learn the very basics of Java programming. Using a book entitled "Programming Video Games for the Evil Genius". I have had an Illegal Start of Expression error that I can't for the life of me get rid of. I have checked the sample code from the book and mine is identical. The error is coming from the for(int i = difficulty; i = 0; i- - ) line. Thanks for helping a newbie out. import javax.swing.*; public class S1P4 {public static void main(String[] args) throws Exception { int difficulty; difficulty = Integer.parseInt(JOptionPane.showInputDialog("How good are you?\n"+ "1 = Great\n"+"10 = Terrible")); boolean cont = false; do { cont = false; double num1 = (int)(Math.round(Math.random()*10)); double num2; do { num2 = (int)(Math.round(Math.random()*10)); } while(num2==0.0); int sign = (int)(Math.round(Math.random()*3)); double answer; System.out.println("\n\n*****"); if(sign==0) { System.out.println(num1+" times "+num2); answer = num1*num2; } else if(sign==1) { System.out.println(num1+" divided by"+num2); answer = num1/num2; } else if(sign==1) { System.out.println(num1+" plus "+num2); answer = num1+num2; } else if(sign==1) { System.out.println(num1+" minus "+num2); answer = num1-num2; } else { System.out.println(num1+" % "+num2); answer = num1%num2; } System.out.println("*****\n"); for(int i = difficulty; i >= 0; i- - ) { System.out.println(i+"..."); Thread.sleep(500); } System.out.println("ANSWER: "+answer); String again; again = JOptionPane.showInputDialog("Play again?"); if(again.equals("yes")) cont = true; } while(cont); } }

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  • SwingWorker exceptions lost even when using wrapper classes

    - by Ti Strga
    I've been struggling with the usability problem of SwingWorker eating any exceptions thrown in the background task, for example, described on this SO thread. That thread gives a nice description of the problem, but doesn't discuss recovering the original exception. The applet I've been handed needs to propagate the exception upwards. But I haven't been able to even catch it. I'm using the SimpleSwingWorker wrapper class from this blog entry specifically to try and address this issue. It's a fairly small class but I'll repost it at the end here just for reference. The calling code looks broadly like try { // lots of code here to prepare data, finishing with SpecialDataHelper helper = new SpecialDataHelper(...stuff...); helper.execute(); } catch (Throwable e) { // used "Throwable" here in desperation to try and get // anything at all to match, including unchecked exceptions // // no luck, this code is never ever used :-( } The wrappers: class SpecialDataHelper extends SimpleSwingWorker { public SpecialDataHelper (SpecialData sd) { this.stuff = etc etc etc; } public Void doInBackground() throws Exception { OurCodeThatThrowsACheckedException(this.stuff); return null; } protected void done() { // called only when successful // never reached if there's an error } } The feature of SimpleSwingWorker is that the actual SwingWorker's done()/get() methods are automatically called. This, in theory, rethrows any exceptions that happened in the background. In practice, nothing is ever caught, and I don't even know why. The SimpleSwingWorker class, for reference, and with nothing elided for brevity: import java.util.concurrent.ExecutionException; import javax.swing.SwingWorker; /** * A drop-in replacement for SwingWorker<Void,Void> but will not silently * swallow exceptions during background execution. * * Taken from http://jonathangiles.net/blog/?p=341 with thanks. */ public abstract class SimpleSwingWorker { private final SwingWorker<Void,Void> worker = new SwingWorker<Void,Void>() { @Override protected Void doInBackground() throws Exception { SimpleSwingWorker.this.doInBackground(); return null; } @Override protected void done() { // Exceptions are lost unless get() is called on the // originating thread. We do so here. try { get(); } catch (final InterruptedException ex) { throw new RuntimeException(ex); } catch (final ExecutionException ex) { throw new RuntimeException(ex.getCause()); } SimpleSwingWorker.this.done(); } }; public SimpleSwingWorker() {} protected abstract Void doInBackground() throws Exception; protected abstract void done(); public void execute() { worker.execute(); } }

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  • Why is Dictionary.First() so slow?

    - by Rotsor
    Not a real question because I already found out the answer, but still interesting thing. I always thought that hash table is the fastest associative container if you hash properly. However, the following code is terribly slow. It executes only about 1 million iterations and takes more than 2 minutes of time on a Core 2 CPU. The code does the following: it maintains the collection todo of items it needs to process. At each iteration it takes an item from this collection (doesn't matter which item), deletes it, processes it if it wasn't processed (possibly adding more items to process), and repeats this until there are no items to process. The culprit seems to be the Dictionary.Keys.First() operation. The question is why is it slow? Stopwatch watch = new Stopwatch(); watch.Start(); HashSet<int> processed = new HashSet<int>(); Dictionary<int, int> todo = new Dictionary<int, int>(); todo.Add(1, 1); int iterations = 0; int limit = 500000; while (todo.Count > 0) { iterations++; var key = todo.Keys.First(); var value = todo[key]; todo.Remove(key); if (!processed.Contains(key)) { processed.Add(key); // process item here if (key < limit) { todo[key + 13] = value + 1; todo[key + 7] = value + 1; } // doesn't matter much how } } Console.WriteLine("Iterations: {0}; Time: {1}.", iterations, watch.Elapsed); This results in: Iterations: 923007; Time: 00:02:09.8414388. Simply changing Dictionary to SortedDictionary yields: Iterations: 499976; Time: 00:00:00.4451514. 300 times faster while having only 2 times less iterations. The same happens in java. Used HashMap instead of Dictionary and keySet().iterator().next() instead of Keys.First().

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  • Painting component inside another component

    - by mike_hornbeck
    I've got a task to display painted 'eyes' with menu buttons to change their colors, and background color. Next animate them. But currently I'm stuck at painting, sinc in my JFrame I've Created JPanel containing panels with drawn eyes and buttons. Buttons are rendered properly but my eyes canvas is not shown. I've tried changing paint to paintComponent, setting contentPane differently but still nothing works. import java.awt.*; import javax.swing.*; public class Main extends JFrame { public static void main(String[] args) { final JFrame frame = new JFrame("Eyes"); frame.setPreferredSize(new Dimension(600, 450)); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JPanel players = new JPanel(new GridLayout(1, 3)); players.add(new JButton("Eyes color")); players.add(new JButton("Eye pupil")); players.add(new JButton("Background color")); JPanel eyes = new JPanel(); Eyes e = new Eyes(); eyes.add(e); eyes.setPreferredSize(new Dimension(600, 400)); JPanel content = new JPanel(); content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS)); frame.setContentPane(content); content.add(players); content.add(eyes); // frame.getContentPane().add(content); frame.pack(); frame.setVisible(true); } } class Eyes extends JPanel { public Eyes(){ } public void paint(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g; g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON); BasicStroke bs = new BasicStroke(3.0f); g2d.setBackground(Color.green); g2d.setStroke(bs); g2d.setColor(Color.yellow); g2d.fillOval(50, 150, 200, 200); g2d.fillOval( 350, 150, 200, 200); g2d.setColor(Color.BLACK); g2d.drawOval(49, 149, 201, 201); g2d.drawOval(349, 149, 201, 201); g2d.fillOval(125, 225, 50, 50); g2d.fillOval(425, 225, 50, 50); } } This is what I should get : This is what I have : When I've tried painting it directly in JFrame it works almost perfect, apart of background not being set. Why setBackgroundColor doesn't influence my drawing in any way ?

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  • File sorting, Comparison method violates its general contract

    - by user2677383
    My file sorting comparator sometimes invoke java.lang.IllegalArgumentException in android app. I cannot figure out the reason. could you explain that? here is my code block: Comparator cc = new Comparator<File>() { @Override public int compare(File f1, File f2) { if (f1.isDirectory() && !f2.isDirectory()) { return 1; } if (f2.isDirectory() && !f1.isDirectory()) { return -1; } if ((f1.isFile() && f2.isFile()) || (f1.isDirectory() && f2.isDirectory())) { if (sort == 1) { return Util.compareFileName(f2.getName(), f1.getName()); } else if (sort == 2) { return (int) (f1.lastModified() - f2.lastModified()); } else if (sort == 3) { return (int) (f2.lastModified() - f1.lastModified()); } else if (sort == 4) { return (int) (f1.length() - f2.length()); } else if (sort == 5) { return (int) (f2.length() - f1.length()); } else return Util.compareFileName(f1.getName(), f2.getName()); } return f1.compareTo(f2); } }; Util.compareFileName is as followings: public static int compareFileName(String s1, String s2) { int thisMarker = 0; int thatMarker = 0; int s1Length = s1.length(); int s2Length = s2.length(); while (thisMarker < s1Length && thatMarker < s2Length) { String thisChunk = getChunk(s1, s1Length, thisMarker); thisMarker += thisChunk.length(); String thatChunk = getChunk(s2, s2Length, thatMarker); thatMarker += thatChunk.length(); // If both chunks contain numeric characters, sort them numerically int result = 0; if (isDigit(thisChunk.charAt(0)) && isDigit(thatChunk.charAt(0))) { // Simple chunk comparison by length. int thisChunkLength = thisChunk.length(); result = thisChunkLength - thatChunk.length(); // If equal, the first different number counts if (result == 0) { for (int i = 0; i < thisChunkLength; i++) { result = thisChunk.charAt(i) - thatChunk.charAt(i); if (result != 0) { return result; } } } } else { result = thisChunk.compareTo(thatChunk); } if (result != 0) return result; } return s1Length - s2Length; }

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  • How solve consumer/producer task using semaphores

    - by user1074896
    I have SimpleProducerConsumer class that illustrate consumer/producer problem (I am not sure that it's correct). public class SimpleProducerConsumer { private Stack<Object> stack = new Stack<Object>(); private static final int STACK_MAX_SIZE = 10; public static void main(String[] args) { SimpleProducerConsumer pc = new SimpleProducerConsumer(); new Thread(pc.new Producer(), "p1").start(); new Thread(pc.new Producer(), "p2").start(); new Thread(pc.new Consumer(), "c1").start(); new Thread(pc.new Consumer(), "c2").start(); new Thread(pc.new Consumer(), "c3").start(); } public synchronized void push(Object d) { while (stack.size() >= STACK_MAX_SIZE) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } stack.push(new Object()); System.out.println("push " + Thread.currentThread().getName() + " " + stack.size()); notify(); } public synchronized Object pop() { while (stack.size() == 0) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(50); } catch (InterruptedException e) { e.printStackTrace(); } stack.pop(); System.out.println("pop " + Thread.currentThread().getName() + " " + stack.size()); notify(); return null; } class Consumer implements Runnable { @Override public void run() { while (true) { pop(); } } } class Producer implements Runnable { @Override public void run() { while (true) { push(new Object()); } } } } I found simple realization of semaphore(here:http://docs.oracle.com/javase/tutorial/essential/concurrency/guardmeth.html I know that there is concurrency package) How I need to change code to exchange java objects monitors to my custom semaphore. (To illustrate C/P problem using semaphores) Semaphore: class Semaphore { private int counter; public Semaphore() { this(0); } public Semaphore(int i) { if (i < 0) throw new IllegalArgumentException(i + " < 0"); counter = i; } public synchronized void release() { if (counter == 0) { notify(); } counter++; } public synchronized void acquire() throws InterruptedException { while (counter == 0) { wait(); } counter--; } }

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  • Extending struts 2 "property" data tag

    - by John B.
    Hi, We are currently developing a project with Struts2. We have a module on which we display a large amount of data on read-only fields from a group of beans via the "property" Struts 2 data tag (i.e. <s:property value="aBeanProperty" /) on a jsp file. In some cases most of the fields might come empty, so a blank is being displayed on screen. Our customer is now requesting us to display default string (i.e. "N/A") whenever a property comes empty, so that it is displayed in place of the blank spaces currently shown. We are looking for a way to achieve this in a clean and maintainable way. The 'property' tag comes with a 'default' attribute on which one can define a default value in cases when the accessed property comes as null. However, most of our properties are empty strings, therefore it does not work in our case. Another solution we are thinking of is to define a base class for all of our beans, and define a util method which will validate if a string is null or empty and then return the default value. Then we would call this method from each bean getter. And yes this would be tiresome and kind of ugly :), therefore we are holding out on this one in case of a better solution. Now, we have in mind a solution which we think would be the best but have not had luck on how implement it. We are planning on extending the 'property' tag some way, defining a new 'default' attribute so that besides working on null properties, it also do so on empty strings ("", " ", etc). Therefore we would only need to replace the original s:property tag with our new custom tag, and the desired result would be achieved without touching java code. Do you have an idea on how to do this? Also, any other clever solution (maybe some sort of design pattern?) on how to default the values of a large amount of property beans are welcome too! (Or maybe, even there might be some tag that does this already in Struts2??) Thanks in advance.

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  • Displaying individual elements of an object in an Arraylist through a for loop?

    - by user1180888
    I'm trying to Display individual elements of an Object I have created. It is a simple Java program that allows users to add and keep track of Player Details. I'm just stumped when it comes to displaying the details after they have been added already. here is what my code looks like I can create the object and input it into the arraylist no problem using the case 2, but when I try to print it out I want to do something like System.out.println("Player Name" + myPlayersArrayList.PlayerName + "Player Position" + myPlayerArrayList.PlayerPosition + "Player Age" + "Player Age"); I know that is not correct, but I dont really know what to do, if anyone can be of any help it would be greatly appreciated. Thanks System.out.println("Welcome to the Football Player database"); System.out.print(System.getProperty("line.separator")); UserInput myFirstUserInput = new UserInput(); int selection; ArrayList<Player> myPlayersArrayList = new ArrayList<Player>(); while (true) { System.out.println("1. View The Players"); System.out.println("2. Add A Player"); System.out.println("3. Edit A Player"); System.out.println("4. Delete A Player"); System.out.println("5. Exit ") ; System.out.print(System.getProperty("line.separator")); selection = myFirstUserInput.getInt("Please select an option"); System.out.print(System.getProperty("line.separator")); switch(selection){ case 1: if (myPlayersArrayList.isEmpty()) { System.out.println("No Players Have Been Entered Yet"); System.out.print(System.getProperty("line.separator")); break;} else {for(int i = 0; i < myPlayersArrayList.size(); i++){ System.out.println(myPlayersArrayList); } break; case 2: { String playerName,playerPos; int playerAge; playerName = (myFirstUserInput.getString("Enter Player name")); playerPos = (myFirstUserInput.getString("Enter Player Position")); playerAge = (myFirstUserInput.getInt("Enter Player Age")); myPlayersArrayList.add(new Player(playerName, playerPos, playerAge)); ; break; }

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  • How to create a Link that supplies its own Markup?

    - by Aranian
    I'm trying to create a link that will hide or show a part of my page. The link should be reusable and display one of two images, depending on state. Adding the two subcomponents on every page where I use the link is kind of clunky so I wanted to create a component that behaves like a link while automatically adding its content. This is the Link component: public class ToggleVisibilityLink extends AjaxFallbackLink<Boolean> { public ToggleVisibilityLink(final String id, final IModel<Boolean> model) { super(id, model); setOutputMarkupId(true); add(new Image("collapseImage") { @Override public boolean isVisible() { return !getModelObject(); } }); add(new Image("expandImage") { @Override public boolean isVisible() { return getModelObject(); } }); } @Override public void onClick(final AjaxRequestTarget target) { setModelObject(!getModelObject()); if (target != null) { target.add(this); send(this.getParent(), Broadcast.EXACT, target); } } } And this is how I currently use it in HTML (this is added to the page or panel where I use the link): <a href="#" wicket:id="collapseExpandLink" class="collapseExpandLink"> <wicket:link> <img src="collapse.png" wicket:id="collapseImage" class="collapseExpandImage collapse"> </wicket:link> <wicket:link> <img src="expand.png" wicket:id="expandImage" class="collapseExpandImage expand"> </wicket:link> </a> And the corresponding Java call: add(new ToggleVisibilityLink("collapseExpandLink", new PropertyModel(this, "hidden"))); But I want to be able to skip the body inside the link as one would have to know about the internals of ToggleVisibilityLink. I experimented with IMarkupResourceStreamProvider, using Dynamic markup in Wicket as a starting point. By googling I found another example where the poster was only able to get that to work when using a Panel, and I was able to do that as well. But I'd really like to keep the link and not package it inside a Panel, as I would not be able to style the link in the markup. I'm also open to alternatives to encapsulate the link and its body.

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  • Terminating a long-executing thread and then starting a new one in response to user changing parameters via UI in an applet

    - by user1817170
    I have an applet which creates music using the JFugue API and plays it for the user. It allows the user to input a music phrase which the piece will be based on, or lets them choose to have a phrase generated randomly. I had been using the following method (successfully) to simply stop and start the music, which runs in a thread using the Player class from JFugue. I generate the music using my classes and user input from the applet GUI...then... private playerThread pthread; private Thread threadPlyr; private Player player; (from variables declaration) public void startMusic(Pattern p) // pattern is a JFugue object which holds the generated music { if (pthread == null) { pthread = new playerThread(); } else { pthread = null; pthread = new playerThread(); } if (threadPlyr == null) { threadPlyr = new Thread(pthread); } else { threadPlyr = null; threadPlyr = new Thread(pthread); } pthread.setPattern(p); threadPlyr.start(); } class playerThread implements Runnable // plays midi using jfugue Player { private Pattern pt; public void setPattern(Pattern p) { pt = p; } @Override public void run() { try { player.play(pt); // takes a couple mins or more to execute resetGUI(); } catch (Exception exception) { } } } And the following to stop music when user presses the stop/start button while Player.isPlaying() is true: public void stopMusic() { threadPlyr.interrupt(); threadPlyr = null; pthread = null; player.stop(); } Now I want to implement a feature which will allow the user to change parameters while the music is playing, create an updated music pattern, and then play THAT pattern. Basically, the idea is to make it simulate "real time" adjustments to the generated music for the user. Well, I have been beating my head against the wall on this for a couple of weeks. I've read all the standard java documentation, researched, read, and searched forums, and I have tried many different ideas, none of which have succeeded. The problem I've run into with all approaches I've tried is that when I start the new thread with the new, updated musical pattern, all the old threads ALSO start, and there is a cacophony of unintelligible noise instead of my desired output. From what I've gathered, the issue seems to be that all the methods I've come across require that the thread is able to periodically check the value of a "flag" variable and then shut itself down from within its "run" block in response to that variable. However, since my thread makes a call that takes several minutes minimum to execute (playing the music), and I need to terminate it WHILE it is executing this, there is really no safe way to do so. So, I'm wondering if there is something I'm missing when it comes to threads, or if perhaps I can accomplish my goal using a totally different approach. Any ideas or guidance is greatly appreciated! Thank you!

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