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• I want my link labels to link to an image saved on my desktop?!?! Is This possible??

  - by JB

  Is it possible to link my labels to and image saved on my desktop??? private void linkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e) { }

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• Is an ArrayList automatically declared static in Java, if it is an instance variable?

  - by Alex

  I'm trying to do something like this: private class aClass { private ArrayList<String> idProd; aClass(ArrayList<String> prd) { this.idProd=new ArrayList<String>(prd); } public ArrayList<String> getIdProd() { return this.idProd; } } So if I have multiple instances of ArrayLIst<String> (st1 ,st2 ,st3) and I want to make new objects of aClass: { aClass obj1,obj2,obj3; obj1=new aClass(st1); obj2=new aClass(st2); obj3=new aClass(st3); } Will all of the aClass objects return st3 if I access the method getIdProd() for each of them(obj1..obj3)? Is an ArrayList as an instance variable automatically declared static?

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• Problem invoking C DLL in C#

  - by CristiC

  I'm currently trying to invoke a method made in C from C# C code looks like this: extern "C" int addSum(int a, int b) { return a*b; } extern "C" int getCount() { return 12; } and C# code looks like this: [DllImport("mydll.dll", SetLastError=true)] private static extern int addSum(IntPtr a, IntPtr b); [DllImport("mydll.dll", SetLastError = true)] private static extern int getCount(); public static int mySum(int a, int b) { return suma(a, b); } public static int getMyCount() { return getCount(); } The code returns the right values but i'm getting the following error: addSum' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature. Any sugestion regarding this issue ? Thanks

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• respond_to? and protected methods

  - by mlomnicki

  It may not be so obvious how respond_to? works in ruby. Consider that: class A def public_method end protected def protected_method end private def private_method end end obj = A.new obj.respond_to?(:public_method) # true - that's pretty obvious obj.respond_to?(:private_method) # false - as expected obj.respond_to?(:protected_method) # true - WTF? So if 'obj' responds to protected_method we should expect obj.protected_method not to raise an exception, shouldn't we? ...but it raises obviously Documentation points that calling respond_to? with 2nd argument set to true check private method as well obj.respond_to?(:private_method, true) # true And that's far more reasonable So the question is how to check if object responds to public method only? Is there a solution better than that? obj.methods.include?(:public_method) # true obj.methods.include?(:protected_method) # false

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• Formatting Field Declarations in Eclipse

  - by geeko

  Greetings Overflowers, Problem: public abstract class Filter { private long id; protected String expression; } how can I align fields automatically in Eclipse, such in: public abstract class Filter { private long id; protected String expression; } Note the space before long, thank you ! UPDATE: I cannot find a customization option to align types of class members (e.g.: long and String) under Eclipse formatter options. Yes, there is one to align names of class members (e.g.: id and expression) but not their types. Please, take a lock at this issue in my examples above. Any solution ?

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• How to detect tab key pressing in C#?

  - by user342325

  I want to detect when tab key is pressed in a textBox and focus the next textbox in the panel. I have tried out keyPressed method and keyDown method. But when I run the program and debug those methods are not calling when the tab key is pressed. Here is my code. private void textBoxName_KeyDown(object sender, KeyEventArgs e) { if (e.KeyCode == Keys.Tab) { textBoxUsername.Focus(); } } private void textBoxName_KeyPress(object sender, KeyPressEventArgs e) { if (e.KeyChar==(char)Keys.Tab) { textBoxUsername.Focus(); } } Please correct me.Thank you.

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• Is there a better way to minimize this C# event repetition?

  - by Damien Wildfire

  I have a lot of code like this: public class Microwave { private EventHandler<EventArgs> _doorClosed; public event EventHandler<EventArgs> DoorClosed { add { lock (this) _doorClosed += value; } remove { lock (this) _doorClosed -= value; } } private EventHandler<EventArgs> _lightbulbOn; public event EventHandler<EventArgs> LightbulbOn { add { lock (this) _lightbulbOn += value; } remove { lock (this) _lightbulbOn -= value; } } // ... } You can see that much of this is boilerplate. In Ruby I'd be able to do something like this: class Microwave has_events :door_closed, :lightbulb_on, ... end Is there a similar shorter way of removing this boilerplate in C#?

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• Items are being replace by another in the Datagridview

  - by stephanie

  When I add the first item in the datagridview its ok but when i add the second one it replace the last item being added. here's my code Private Sub add() Dim i As Integer For i = 0 To DataGridView1.Rows.Count - 1 'DataGridView1.Rows.Add() DataGridView1.Rows(DataGridView1.RowCount - 1).Cells("TransID").Value = txttrans.Text DataGridView1.Rows(DataGridView1.RowCount - 1).Cells("ProductCode").Value = txtprodcode.Text DataGridView1.Rows(DataGridView1.RowCount - 1).Cells("ProductName").Value = cmbprodname.Text DataGridView1.Rows(DataGridView1.RowCount - 1).Cells("Quantity").Value = txtqty.Text DataGridView1.Rows(DataGridView1.RowCount - 1).Cells("Price").Value = txtprc.Text DataGridView1.Rows(DataGridView1.RowCount - 1).Cells("Amount").Value = txtat.Text DataGridView1.Rows(DataGridView1.RowCount - 1).Cells("CustomerName").Value = txtcust.Text DataGridView1.Rows(DataGridView1.RowCount - 1).Cells("Date1").Value = txtdate.Text Next i End Sub And this is in my ADDbutton: Private Sub btnadd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnadd.Click Try add() Catch ex As Exception MessageBox.Show(ex.Message) End Try Dim total As Integer For Each row As DataGridViewRow In DataGridView1.Rows total += row.Cells("Amount").Value Next txtamt.Text = total

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• mx.core::BitmapAsset could not be found

  - by asksuperuser

  I tried the code EmbedAssets.as below found in sample here: http://www.senocular.com/flash/tutorials/as3withmxmlc/ I got this error when building with mxmlc.exe and testing the ouput EmbedAssets.swf in Flash Player 9: VerifyError: Error #1014: mx.core::BitmapAsset could not be found package { import flash.display.Sprite; public class EmbedAssets extends Sprite { [Embed(source="images/trophy.png")] private var TrophyImage:Class; [Embed(source="swfs/satdish.swf")] private var SatelliteAnimation:Class; public function EmbedAssets() { addChild(new SatelliteAnimation()); addChild(new TrophyImage()); } } } satdish.swf is not corrupted so I don't understand why this error message.

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• How do we name test methods where we are checking for more than one condition?

  - by Sandbox

  I follow the technique specified in Roy Osherove's The Art Of Unit Testing book while naming test methods - MethodName_Scenario_Expectation. It suits perfectly well for my 'unit' tests. But,for tests that I write in 'controller' or 'coordinator' class, there isn't necessarily a method which I want to test. For these tests, I generate multiple conditions which make up one scenario and then I verify the expectation. For example, I may set some properties on different instances, generate an event and then verify that my expectation from controller/coordinator is being met. Now, my controller handles events using a private event handler. Here my scenario is that, I set some properties, say 3 condition1,condition2 and condition3 Also, my scenario includes an event is raised I don't have a method name as my event handler is private. How do I name such a test method?

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• Android Thumbnail Loading Problem

  - by y ramesh rao

  I'm using a thumbnail loader in my project the one mentioned below. The problem is that the it loads all the thumbnails properly except the ones who's size is of about 40K. When our back end is giving that sort of thumbnails are not generated and sometimes this eventually leads to a Crash too. What m I supposed to do with this ? public class ThumbnailManager { private final Map<String, Bitmap> drawableMap; public static Context context; private Resources res; private int thumbnail_size; public ThumbnailManager() { drawableMap = new HashMap<String, Bitmap >(); res = new Resources(context.getAssets(), null, null); thumbnail_size = res.getInteger(R.ThumbnailManager.THUMBNAIL_SIZE); } public Bitmap fetchBitmap(String urlString) { if(drawableMap.containsKey(urlString)) { return (drawableMap.get(urlString)); } //Log.d(getClass().getSimpleName(), " Image URL :: "+ urlString); try { InputStream is = fetch(urlString); android.util.Log.v("ThumbnailManager", "ThumbnailManager " + urlString); drawableMap.put(urlString, BitmapFactory.decodeStream(is));//Bitmap.createScaledBitmap(BitmapFactory.decodeStream(is), thumbnail_size, thumbnail_size, false)); return drawableMap.get(urlString); } catch(Exception e) { android.util.Log.v("EXCEPTION", "EXCEPTION" + urlString); return null; } } public void fetchBitmapOnThread(final String urlString, final ImageView imageView) { if(drawableMap.containsKey(urlString)) { imageView.setImageBitmap(drawableMap.get(urlString)); return; } if(urlString.compareTo("AUDIO") == 0) { Bitmap audioThumb = BitmapFactory.decodeResource(context.getResources(), R.drawable.timeline_audio_thumb); drawableMap.put(urlString, Bitmap.createScaledBitmap(audioThumb, thumbnail_size, thumbnail_size, false)); imageView.setImageBitmap(drawableMap.get(urlString)); return; } final Handler handler = new Handler() { public void handleMessage(Message message) { imageView.setImageBitmap((Bitmap) message.obj); } }; Thread thread = new Thread() { public void run() { Bitmap urlBitmap = fetchBitmap(urlString); Message message = handler.obtainMessage(1, urlBitmap); handler.sendMessage(message); } }; thread.start(); } public InputStream fetch(String urlString) throws IOException, MalformedURLException { final URL url = new URL(urlString); final URLConnection conn = url.openConnection(); HttpURLConnection httpConn = (HttpURLConnection) conn; httpConn.setAllowUserInteraction(true); httpConn.setInstanceFollowRedirects(true); httpConn.setRequestMethod("GET"); httpConn.connect(); return(conn.getInputStream()); } }

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• Java compiler rejects variable declaration with parameterized inner class

  - by Johansensen

  I have some Groovy code which works fine in the Groovy bytecode compiler, but the Java stub generated by it causes an error in the Java compiler. I think this is probably yet another bug in the Groovy stub generator, but I really can't figure out why the Java compiler doesn't like the generated code. Here's a truncated version of the generated Java class (please excuse the ugly formatting): @groovy.util.logging.Log4j() public abstract class AbstractProcessingQueue <T> extends nz.ac.auckland.digitizer.AbstractAgent implements groovy.lang.GroovyObject { protected int retryFrequency; protected java.util.Queue<nz.ac.auckland.digitizer.AbstractProcessingQueue.ProcessingQueueMember<T>> items; public AbstractProcessingQueue (int processFrequency, int timeout, int retryFrequency) { super ((int)0, (int)0); } private enum ProcessState implements groovy.lang.GroovyObject { NEW, FAILED, FINISHED; } private class ProcessingQueueMember<E> extends java.lang.Object implements groovy.lang.GroovyObject { public ProcessingQueueMember (E object) {} } } The offending line in the generated code is this: protected java.util.Queue<nz.ac.auckland.digitizer.AbstractProcessingQueue.ProcessingQueueMember<T>> items; which produces the following compile error: [ERROR] C:\Documents and Settings\Administrator\digitizer\target\generated-sources\groovy-stubs\main\nz\ac\auckland\digitizer\AbstractProcessingQueue.java:[14,96] error: improperly formed type, type arguments given on a raw type The column index of 96 in the compile error points to the <T> parameterization of the ProcessingQueueMember type. But ProcessingQueueMember is not a raw type as the compiler claims, it is a generic type: private class ProcessingQueueMember <E> extends java.lang.Object implements groovy.lang.GroovyObject { ... I am very confused as to why the compiler thinks that the type Queue<ProcessingQueueMember<T>> is invalid. The Groovy source compiles fine, and the generated Java code looks perfectly correct to me too. What am I missing here? Is it something to do with the fact that the type in question is a nested class? (in case anyone is interested, I have filed this bug report relating to the issue in this question) Edit: Turns out this was indeed a stub compiler bug- this issue is now fixed in 1.8.9, 2.0.4 and 2.1, so if you're still having this issue just upgrade to one of those versions. :)

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• C++Template in Java?

  - by RnMss

  I want something like this: public abstract class ListenerEx<LISTENER, PARENT> implements LISTENER { PARENT parent; public ListenerEx(PARENT p) { parent = p; } } But it doesn't compile. Is there a better solution? Is there something in Java like C++ template that would do check syntax after template deduction? The following explains why I need such a ListenerEX class, if you already know what it is, you don't need to read the following. I have a main window, and a button on it, and I want to get access to some method of the main window's within the listener: public class MainWindow extends JFrame { public void doSomething() { /* ... */ } public void doSomethingElse() { /* ... */ } private JButton button; public MainWindow() { button = new JButton(...); add(button); button.setActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { doSomething(); doSomethingElse(); } }); } } This would compile but does not work properly all the time. (Why would it compile when the ActionListener does not have doSomething() method?) Of course we can do it like this: public class MainWindow extends JFrame { public void doSomething() { } public void doSomethingElse() { } private JButton button; public MainWindow() { button = new JButton(...); add(button); class ActionListener1 implements ActionListener { MainWindow parent; public ActionListener(MainWindow p) { parent = p; } public void actionPerformed(ActionEvent e) { parent.doSomething(); parent.doSomethingElse(); } } button.setActionListener(new ActionListener1(this)); } } However I hate this style ... So I tried: public abstract class ActionListenerEx<P> implements ActionListener { P parent; public ActionListenerEx(P p) { parent = p; } } public class MainWindow extends JFrame { public void doSomething() { } public void doSomethingElse() { } private JButton button; public MainWindow() { button = new JButton(...); add(button); button.setActionListener(new ActionListenerEx<MainWindow>(this) { public void actionPerformed(ActionEvent e) { parent.doSomething(); parent.doSomethingElse(); } }); } } But there's lots of Listeners beside the ActionListener ... public abstract class ActionListenerEx<LISTENER, PARENT> implements LISTENER { PARENT parent; public ActionListenerEx(PARENT p) { parent = p; } } However, it won't compile ... I am fresh at Java, and I wonder if there's already better solution.

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• Fastest way to move records from a oracle DB into MS sql server after processing

  - by user347748

  Hi.. Ok this is the scenario...I have a table in Oracle that acts like a queue... A VB.net program reads the queue and calls a stored proc in MS SQL Server that processes and then inserts the message into another SQL server table and then deletes the record from the oracle table. We use a datareader to read the records from Oracle and then call the stored proc for each of the records. The program seems to be a little slow. The stored procedure itself isnt slow. The SP by itself when called in a loop can process about 2000 records in 20 seconds. BUt when called from the .Net program, the execution time is about 5 records per second. I have seen that most of the time consumed is in calling the stored procedure and waiting for it to return. Is there a better way of doing this? Here is a snippet of the actual code Function StartDataXfer() As Boolean Dim status As Boolean = False Try SqlConn.Open() OraConn.Open() c.ErrorLog(Now.ToString & "--Going to Get the messages from oracle", 1) If GetMsgsFromOracle() Then c.ErrorLog(Now.ToString & "--Got messages from oracle", 1) If ProcessMessages() Then c.ErrorLog(Now.ToString & "--Finished Processing all messages in the queue", 0) status = True Else c.ErrorLog(Now.ToString & "--Failed to Process all messages in the queue", 0) status = False End If Else status = True End If StartDataXfer = status Catch ex As Exception Finally SqlConn.Close() OraConn.Close() End Try End Function Private Function GetMsgsFromOracle() As Boolean Try OraDataAdapter = New OleDb.OleDbDataAdapter OraDataTable = New System.Data.DataTable OraSelCmd = New OleDb.OleDbCommand GetMsgsFromOracle = False With OraSelCmd .CommandType = CommandType.Text .Connection = OraConn .CommandText = GetMsgSql End With OraDataAdapter.SelectCommand = OraSelCmd OraDataAdapter.Fill(OraDataTable) If OraDataTable.Rows.Count > 0 Then GetMsgsFromOracle = True End If Catch ex As Exception GetMsgsFromOracle = False End Try End Function Private Function ProcessMessages() As Boolean Try ProcessMessages = False PrepareSQLInsert() PrepOraDel() i = 0 Dim Method As Integer Dim OraDataRow As DataRow c.ErrorLog(Now.ToString & "--Going to call message sending procedure", 2) For Each OraDataRow In OraDataTable.Rows With OraDataRow Method = GetMethod(.Item(0)) SQLInsCmd.Parameters("RelLifeTime").Value = c.RelLifetime SQLInsCmd.Parameters("Param1").Value = Nothing SQLInsCmd.Parameters("ID").Value = GenerateTransactionID() ' Nothing SQLInsCmd.Parameters("UID").Value = Nothing SQLInsCmd.Parameters("Param").Value = Nothing SQLInsCmd.Parameters("Credit").Value = 0 SQLInsCmd.ExecuteNonQuery() 'check the return value If SQLInsCmd.Parameters("ReturnValue").Value = 1 And SQLInsCmd.Parameters("OutPutParam").Value = 0 Then 'success 'delete the input record from the source table once it is logged c.ErrorLog(Now.ToString & "--Moved record successfully", 2) OraDataAdapter.DeleteCommand.Parameters("P(0)").Value = OraDataRow.Item(6) OraDataAdapter.DeleteCommand.ExecuteNonQuery() c.ErrorLog(Now.ToString & "--Deleted record successfully", 2) OraDataAdapter.Update(OraDataTable) c.ErrorLog(Now.ToString & "--Committed record successfully", 2) i = i + 1 Else 'failure c.ErrorLog(Now.ToString & "--Failed to exec: " & c.DestIns & "Status: " & SQLInsCmd.Parameters("OutPutParam").Value & " and TrackId: " & SQLInsCmd.Parameters("TrackID").Value.ToString, 0) End If If File.Exists("stop.txt") Then c.ErrorLog(Now.ToString & "--Stop File Found", 1) 'ProcessMessages = True 'Exit Function Exit For End If End With Next OraDataAdapter.Update(OraDataTable) c.ErrorLog(Now.ToString & "--Updated Oracle Table", 1) c.ErrorLog(Now.ToString & "--Moved " & i & " records from Oracle to SQL Table", 1) ProcessMessages = True Catch ex As Exception ProcessMessages = False c.ErrorLog(Now.ToString & "--MoveMsgsToSQL: " & ex.Message, 0) Finally OraDataTable.Clear() OraDataTable.Dispose() OraDataAdapter.Dispose() OraDelCmd.Dispose() OraDelCmd = Nothing OraSelCmd = Nothing OraDataTable = Nothing OraDataAdapter = Nothing End Try End Function Public Function GenerateTransactionID() As Int64 Dim SeqNo As Int64 Dim qry As String Dim SqlTransCmd As New OleDb.OleDbCommand qry = " select seqno from StoreSeqNo" SqlTransCmd.CommandType = CommandType.Text SqlTransCmd.Connection = SqlConn SqlTransCmd.CommandText = qry SeqNo = SqlTransCmd.ExecuteScalar If SeqNo > 2147483647 Then qry = "update StoreSeqNo set seqno=1" SqlTransCmd.CommandText = qry SqlTransCmd.ExecuteNonQuery() GenerateTransactionID = 1 Else qry = "update StoreSeqNo set seqno=" & SeqNo + 1 SqlTransCmd.CommandText = qry SqlTransCmd.ExecuteNonQuery() GenerateTransactionID = SeqNo End If End Function Private Function PrepareSQLInsert() As Boolean 'function to prepare the insert statement for the insert into the SQL stmt using 'the sql procedure SMSProcessAndDispatch Try Dim dr As DataRow SQLInsCmd = New OleDb.OleDbCommand With SQLInsCmd .CommandType = CommandType.StoredProcedure .Connection = SqlConn .CommandText = SQLInsProc .Parameters.Add("ReturnValue", OleDb.OleDbType.Integer) .Parameters("ReturnValue").Direction = ParameterDirection.ReturnValue .Parameters.Add("OutPutParam", OleDb.OleDbType.Integer) .Parameters("OutPutParam").Direction = ParameterDirection.Output .Parameters.Add("TrackID", OleDb.OleDbType.VarChar, 70) .Parameters.Add("RelLifeTime", OleDb.OleDbType.TinyInt) .Parameters("RelLifeTime").Direction = ParameterDirection.Input .Parameters.Add("Param1", OleDb.OleDbType.VarChar, 160) .Parameters("Param1").Direction = ParameterDirection.Input .Parameters.Add("TransID", OleDb.OleDbType.VarChar, 70) .Parameters("TransID").Direction = ParameterDirection.Input .Parameters.Add("UID", OleDb.OleDbType.VarChar, 20) .Parameters("UID").Direction = ParameterDirection.Input .Parameters.Add("Param", OleDb.OleDbType.VarChar, 160) .Parameters("Param").Direction = ParameterDirection.Input .Parameters.Add("CheckCredit", OleDb.OleDbType.Integer) .Parameters("CheckCredit").Direction = ParameterDirection.Input .Prepare() End With Catch ex As Exception c.ErrorLog(Now.ToString & "--PrepareSQLInsert: " & ex.Message) End Try End Function Private Function PrepOraDel() As Boolean OraDelCmd = New OleDb.OleDbCommand Try PrepOraDel = False With OraDelCmd .CommandType = CommandType.Text .Connection = OraConn .CommandText = DelSrcSQL .Parameters.Add("P(0)", OleDb.OleDbType.VarChar, 160) 'RowID .Parameters("P(0)").Direction = ParameterDirection.Input .Prepare() End With OraDataAdapter.DeleteCommand = OraDelCmd PrepOraDel = True Catch ex As Exception PrepOraDel = False End Try End Function WHat i would like to know is, if there is anyway to speed up this program? Any ideas/suggestions would be highly appreciated... Regardss, Chetan

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• Issues querying Access '07 database in C#

  - by Kye

  I'm doing a .NET unit as part of my studies. I've only just started, with a lecturer that as kinda failed to give me the most solid foundation with .NET, so excuse the noobishness. I'm making a pretty simple and generic database-driven application. I'm using C# and I'm accessing a Microsoft Access 2007 database. I've put the database-ish stuff in its own class with the methods just spitting out OleDbDataAdapters that I use for committing. I feed any methods which preform a query a DataSet object from the main program, which is where I'm keeping the data (multiple tables in the db). I've made a very generic private method that I use to perform SQL SELECT queries and have some public methods wrapping that method to get products, orders.etc (it's a generic retail database). The generic method uses a separate Connect method to actually make the connection, and it is as follows: private static OleDbConnection Connect() { OleDbConnection conn = new OleDbConnection( @"Provider=Microsoft.ACE.OLEDB.12.0; Data Source=C:\Temp\db.accdb"); return conn; } The generic method is as follows: private static OleDbDataAdapter GenericSelectQuery( DataSet ds, string namedTable, String selectString) { OleDbCommand oleCommand = new OleDbCommand(); OleDbConnection conn = Connect(); oleCommand.CommandText = selectString; oleCommand.Connection = conn; oleCommand.CommandType = CommandType.Text; OleDbDataAdapter adapter = new OleDbDataAdapter(); adapter.SelectCommand = oleCommand; adapter.MissingSchemaAction = MissingSchemaAction.AddWithKey; adapter.Fill(ds, namedTable); return adapter; } The wrapper methods just pass along the DataSet that they received from the main program, the namedtable string is the name of the table in the dataset, and you pass in the query you wish to make. It doesn't matter which query I give it (even something simple like SELECT * FROM TableName) I still get thrown an OleDbException, stating that there was en error with the FROM clause of the query. I've just resorted to building the queries with Access, but there's still no use. Obviously there's something wrong with my code, which wouldn't actually surprise me. Here are some wrapper methods I'm using. public static OleDbDataAdapter GetOrderLines(DataSet ds) { OleDbDataAdapter adapter = GenericSelectQuery( ds, "orderlines", "SELECT OrderLine.* FROM OrderLine;"); return adapter; } They all look the same, it's just the SQL that changes.

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• C# Type Casting at Runtimefor Array.SetValue

  - by sprocketonline

  I'm trying to create an array using reflection, and insert values into it. I'm trying to do this for many different types so would like a createAndFillArray function capable of this : Type t1 = typeof(A); Type t2 = typeof(B); double exampleA = 22.5; int exampleB = 43; Array arrA = createAndFillArray(t1, exampleA); Array arrB = createAndFillArray(t2, exampleB); private Array createAndFillArray(Type t, object val){ Array arr = Array.CreateInstance( t, 1); //length 1 in this example only, real-world is of variable length. arr.SetValue( val, 0 ); //this causes the following error: "System.InvalidCastException : Object cannot be stored in an array of this type." return arr; } with the class A being as follows: public class A{ public A(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator A(double d){ A a = new A(); a.Value = d; return a; } } and class B being very similar, but with int: public class B{ public B(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator B(double d){ B b = new B(); b.Value = d; return b; } } I hoped that the implicit operator would have ensured that the double be converted to class A, or the int to class B, and the error avoided; but this is obviously not so. The above is used in a custom deserialization class, which takes data from a custom data format and fills in the corresponding .Net object properties. I'm doing this via reflection and at runtime, so I think both are unavoidable. I'm targeting the C# 2.0 framework. I've dozens, if not hundreds, of classes similar to A and B, so would prefer to find a solution which improved on the createAndFillArray method rather than a solution which altered these classes.

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• How to work with PHP abstract?

  - by YumYumYum

  Why would you use such abstract? Does it speed up work or what exactly its for? // file1.php abstract class Search_Adapter_Abstract { private $ch = null; abstract private function __construct() { } abstract public funciton __destruct() { curl_close($this->ch); } abstract public function search($searchString,$offset,$count); } // file2.php include("file1.php"); class abc extends Search_Adapter_Abstract { // Will the curl_close now automatically be closed? } What is the reason of extending abstract here? Makes me confused. What can i get from it now?

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• Task.wait not working as I imagined

  - by user2357446

  I am trying to download a file, wait for the file to finish downloading, and then read the file afterwards. I have the following methods to do this: private async Task startDownload(string link, string savePath) { WebClient client = new WebClient(); client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(client_DownloadProgressChanged); client.DownloadFileCompleted += new AsyncCompletedEventHandler(client_DownloadFileCompleted); await client.DownloadFileTaskAsync(new Uri(link), savePath); } private void checkUpdateButton_Click(object sender, EventArgs e) { Task task = Task.Factory.StartNew(() => startDownload(versionLink, versionSaveTo)); task.Wait(); if (task.IsCompleted) { checkVersion(); } } The checkVersion() method reads the file that was downloaded. This is throwing an IOException saying that the file is in use by something else and cannot be read. I thought that having task.Wait would prevent the rest of the method from executing until the task was finished?

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• Swing: does DefaultBoundedRangeModel coalesce multiple events?

  - by Jason S

  I have a JProgressBar displaying a BoundedRangeModel which is extremely fine grained and I was concerned that updating it too often would slow down my computer. So I wrote a quick test program (see below) which has a 10Hz timer but each timer tick makes 10,000 calls to microtick() which in turn increments the BoundedRangeModel. Yet it seems to play nicely with a JProgressBar; my CPU is not working hard to run the program. How does JProgressBar or DefaultBoundedRangeModel do this? They seem to be smart about how much work it does to update the JProgressBar, so that as a user I don't have to worry about updating the BoundedRangeModel's value. package com.example.test.gui; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.BoundedRangeModel; import javax.swing.DefaultBoundedRangeModel; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JProgressBar; import javax.swing.Timer; public class BoundedRangeModelTest1 extends JFrame { final private BoundedRangeModel brm = new DefaultBoundedRangeModel(); final private Timer timer = new Timer(100, new ActionListener() { @Override public void actionPerformed(ActionEvent arg0) { tick(); } }); public BoundedRangeModelTest1(String title) { super(title); JPanel p = new JPanel(); p.add(new JProgressBar(this.brm)); getContentPane().add(p); this.brm.setMaximum(1000000); this.brm.setMinimum(0); this.brm.setValue(0); } protected void tick() { for (int i = 0; i < 10000; ++i) { microtick(); } } private void microtick() { this.brm.setValue(this.brm.getValue()+1); } public void start() { this.timer.start(); } static public void main(String[] args) { BoundedRangeModelTest1 f = new BoundedRangeModelTest1("BoundedRangeModelTest1"); f.pack(); f.setVisible(true); f.setDefaultCloseOperation(EXIT_ON_CLOSE); f.start(); } }

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• Linked lists in Java - Help with writing methods

  - by user368241

  Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (I will add methods gradually according to my specific questions) (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations. 1) public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. Here is my try : public int indexOf (int ch) { int count = 0; charNode pos = _head; if (pos == null ) { return -1; } for (pos = _head; pos!=null && pos.getData()!=ch; pos = pos.getNext()) { count = count + pos.getValue(); } if (pos==null) return -1; return count; } Time complexity = O(N) Space complexity = O(1) EDIT : I have a problem. I tested it in BlueJ and if the char ch doesn't appear it returns -1 but if it does, it always returns 0 and I don't understand why... I am confused. How can the compiler know that the value is the number of times the letter appears consecutively? Can I assume this because its given on the question or what? If it's true and I can assume this, then my code should be correct right? Ok I just spoke with my instructor and she said it isn't required to write it in the exercise but in order for me to test that it indeed works, I need to open a new class and write a code for making a list so that the the value of every node is the number of times the letter appears consecutively. Can someone please assist me? So I will copy+paste to BlueJ and this way I will be able to test all the methods. Meanwhile I am moving on to the next methods. 2) public int indexOf (int ch, int fromIndex) - returns the index in the string it is operated on of the first appeareance of the char "ch", as the search begins in the index "fromIndex". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex doesn't appear in the range, returns -1. Here is my try: public int indexOf (int ch, int fromIndex) { int count = 0, len=0, i; charNode pos = _head; CharNode cur = _head; for (pos = _head; pos!=null; pos = pos.getNext()) { len = len+1; } if (fromIndex<0 || fromIndex>=len) return -1; for (i=0; i<fromIndex; i++) { cur = cur.getNext(); } if (cur == null ) { return -1; } for (cur = _head; cur!=null && cur.getData()!=ch; cur = cur.getNext()) { count = count + cur.getValue(); } if (cur==null) return -1; return count; } Time complexity = O(N) ? Space complexity = O(1) 3) public StringList concat (String str) - returns a string that consists of the string that it is operated on and in its end the string "str" is concatenated. Here is my try : public StringList concat (String str) { String str = ""; charNode pos = _head; if (str == null) return -1; for (pos = _head; pos!=null; pos = pos.getNext()) { str = str + pos.getData(); } str = str + "str"; return str; } Time complexity = O(N) Space complexity = O(1)

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• Circular Tally Counter Not Rolling Over

  - by chris ward

  I was practicing my java and was trying to make a simple counter with rollover at max, but for some reason it isn't rolling over. Any advice? public class HandTallyCounter { private int max; private int count; public HandTallyCounter(int max) { this.max = max; count = 0; } public void click() { if (count++ > max) { count = 0; } } public int getCount() { return count; } public void reset() { count = 0; } }

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• Java: how to represent graphs?

  - by Rosarch

  I'm implementing some algorithms to teach myself about graphs and how to work with them. What would you recommend is the best way to do that in Java? I was thinking something like this: public class Vertex { private ArrayList<Vertex> outnodes; //Adjacency list. if I wanted to support edge weight, this would be a hash map. //methods to manipulate outnodes } public class Graph { private ArrayList<Vertex> nodes; //algorithms on graphs } But I basically just made this up. Is there a better way? Also, I want it to be able to support variations on vanilla graphs like digraphs, weighted edges, multigraphs, etc.

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• Classes as a compilation unit

  - by Yannbane

  If "compilation unit" is unclear, please refer to this. However, what I mean by it will be clear from the context. Edit: my language allows for multiple inheritance, unlike Java. I've started designing+developing my own programming language for educational, recreational, and potentially useful purposes. At first, I've decided to base it off Java. This implied that I would have all the code be written inside classes, and that code compiles to classes, which are loaded by the VM. However, I've excluded features such as interfaces and abstract classes, because I found no need for them. They seemed to be enforcing a paradigm, and I'd like my language not to do that. I wanted to keep the classes as the compilation unit though, because it seemed convenient to implement, familiar, and I just liked the idea. Then I noticed that I'm basically left with a glorified module system, where classes could be used either as "namespaces", providing constants and functions using the static directive, or as templates for objects that need to be instantiated ("actual" purpose of classes in other languages). Now I'm left wondering: what are the benefits of having classes as compilation units? (Also, any general commentary on my design would be much appreciated.)

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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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• What is the explanation of this results in Java ?

  - by M.H

  I have the following code : public class Main { private int i = j; //1 private int j = 10; public static void main(String[] args) { System.out.println((new Main()).i); } } and there is a compiler error in line 1 because an illegal forward reference. But when I am trying the following code : public class Main { int i = getJ(); //1 int getJ(){ return j; } int j=10; public static void main(String[] args) { System.out.println(new Main().i); } } it works fine and the result is 0.Why there is no illegal forward reference in line 1 here?.The two codes look similar to me.

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