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  • How are ambigous methods resolved in java ?

    - by Jijoy
    Hi, I have a question. package org.study.algos; public class Study { public static void main(String[] args) { A a = new A(); a.m1(null); } } class A { public void m1(String s) { System.out.println("String"); System.out.println(s); } public void m1(Object obj) { System.out.println("Object"); System.out.println(obj); } } Here, the output is String null Why does the JVM resolve the method to one with a String argument? Thanks in advance J

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  • Arguments against Create or Update

    - by Nix
    Recently someone stated that they thought all Creates should be CreateOrUpdates. Instinctively i thought bad, but now I am trying to find out if I have any grounds. Situation interface IService{ void Create(Object a); void Update(Object a); } or interface IService{ void CreateOrUpdate(Object a); } My first thought is if you implemented everything CreateOrUpdate then you have no control if someone accidentally sends you wrong data, or concurrency issues where someone changes a "primary" field right before you call update.... But if you remove those cases, are there any other cons?

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  • Mvp View knows Model

    - by userbb
    I'm trying to use MVP and I notice that my View must know Model that should not happen in MVP I presume. here is example: public partial class TestForm : Form, ITestPresenter { public void LoadList(IEnumerable<AppSignature> data) { testPresenterBindingSource.DataSource = data; } } public interface ITestPresenter { event EventHandler<EventArgs> Load; void LoadList(IEnumerable<AppSignature> data); } and the problem is that in TestForm I need reference to AppSignature. In all tutorials I saw, there are some simple examples like public void LoadList(IEnumerable<String> data) where there is no need reference to model. But how i.e DataGridView can publish current row data?

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  • How to Execute Base Class's ExtractPageData() Before Implementors's ExtractPageData()?

    - by DaveDev
    I have the following page public partial class GenericOfflineCommentary : OfflineFactsheetBase { } where OfflineFactsheetBase is defined as public class OfflineFactsheetBase : System.Web.UI.Page { public OfflineFactsheetBase() { this.Load += new EventHandler(this.Page_Load); this.PreInit += new EventHandler(this.Page_PreInit); } protected void Page_PreInit(object sender, EventArgs e) { if (Request.QueryString["data"] != null) { this.PageData = StringCompressor.DecompressString(Request.QueryString["data"]); this.ExtractPageData(); } } } OfflineFactsheetBase has the following virtual method: public virtual void ExtractPageData() { // get stuff relevant to all pages that impmement OfflineFactsheetBase } which is implemented in all pages that impmement OfflineFactsheetBase as follows: public partial class GenericOfflineCommentary : OfflineFactsheetBase { public override void ExtractPageData() { // get stuff relevant to an OfflineCommentary page. } } Currently, only GenericOfflineCommentary's ExtractPageData() is firing. How can I modify this to first run OfflineFactsheetBase's ExtractPageData() and then GenericOfflineCommentary's?

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  • Java Timer not working

    - by Jacob
    I have an Image named worldImageToUse and I have a Timer that is supposed to toggle worldImageToUse between two images every 1 second. But it does not seem to work. Help Please? public void startWorldImageFlash() { worldImageFlashTimer = new Timer(); TimerTask task = new TimerTask() { @Override public void run() { if(worldImageToUse == worldImage) setWorldImageBW(); if(worldImageToUse == worldImageBW) setWorldImageColor(); } }; worldImageFlashTimer.scheduleAtFixedRate(task, 0, 1000); } public void stopWorldImageFlash() { worldImageFlashTimer.cancel(); setWorldImageColor(); }

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  • Java SWING- Create a function to add elements to JScrollPanel ??? PLEASE

    - by battousai622
    I want to create a function so that i can call add JLables, ect inside the JScrollPanel. Im not sure what the command is in netbeans. I tried doing JScrollPanel - events - container - componentAdded to create the code below. But nothing shows up when i add code to that function. Any help would be great please! =] private void initComponents() { scrollPanel = new javax.swing.JScrollPane(); scrollPanel.addContainerListener(new java.awt.event.ContainerAdapter() { public void componentAdded(java.awt.event.ContainerEvent evt) { scrollPanelComponentAdded(evt); } } private void scrollPanelComponentAdded(java.awt.event.ContainerEvent evt) { System.out.println("main"); }

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  • Java Swing- Create a function to add elements to JScrollPanel

    - by battousai622
    I want to create a function so that i can call add JLabel's, etc inside the JScrollPanel. I am not sure what the command is in NetBeans. I tried doing JScrollPanel - events - container - componentAdded to create the code below. But nothing shows up when i add code to that function. private void initComponents() { scrollPanel = new javax.swing.JScrollPane(); scrollPanel.addContainerListener(new java.awt.event.ContainerAdapter() { public void componentAdded(java.awt.event.ContainerEvent evt) { scrollPanelComponentAdded(evt); } } private void scrollPanelComponentAdded(java.awt.event.ContainerEvent evt) { System.out.println("main"); } Any help would be great, thanks.

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  • Dynamic Object Not Creating for Privately Inherited Class.

    - by mahesh
    Hi, What is the reason for the following code that does not let me to create object. class base { public: void foo() { cout << "base::foo()"; } }; class derived : private base { public: void foo() { cout << "deived::foo()"; } }; void main() { base *d = new derived(); d->foo(); } It Gives me error : " 'type cast' : conversion from 'derived *' to 'base *' exists, but is inaccessible" Thanks in advance :)

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  • How do I find out if an object can be Invoke()'d?

    - by Jurily
    Consider the following class: public class Event<T> { public delegate void Handler<t>(t msg); private event Handler<T> E; public void connect(Delegate handler) { E += delegate(T msg) { object target = handler.Target; if (Invokable(target) { target.BeginInvoke(handler, new object[] { msg }); } }; } public void emit(T msg) { if ( E != null ) { E(msg); } } private static bool Invokable(object o) { // magic } } How do I implement Invokable(), and what else do I need for this code to compile?

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  • How to Execute Base Class's Method Before Implementors's Method?

    - by DaveDev
    I have the following page public partial class GenericOfflineCommentary : OfflineFactsheetBase { } where OfflineFactsheetBase is defined as public class OfflineFactsheetBase : System.Web.UI.Page { public OfflineFactsheetBase() { this.Load += new EventHandler(this.Page_Load); this.PreInit += new EventHandler(this.Page_PreInit); } protected void Page_PreInit(object sender, EventArgs e) { if (Request.QueryString["data"] != null) { this.PageData = StringCompressor.DecompressString(Request.QueryString["data"]); this.ExtractPageData(); } } } OfflineFactsheetBase has the following virtual method: public virtual void ExtractPageData() { // get stuff relevant to all pages that impmement OfflineFactsheetBase } which is implemented in all pages that impmement OfflineFactsheetBase as follows: public partial class GenericOfflineCommentary : OfflineFactsheetBase { public override void ExtractPageData() { // get stuff relevant to an OfflineCommentary page. } } Currently, only GenericOfflineCommentary's ExtractPageData() is firing. How can I modify this to first run OfflineFactsheetBase's ExtractPageData() and then GenericOfflineCommentary's? edit: I'm trying to avoid having to call base.ExtractPageData() in every implementor. Is this possible?

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  • Why baseclass calls method of subclass?

    - by twlkyao
    I encounter some code like the following: BaseClass: public class BaseClass { String name = "Base"; public BaseClass() { printName(); } public void printName() { System.out.println(name + "——Base"); } } DrivedClass: public class SubClass extends BaseClass { String name = "Sub"; public SubClass() { printName(); } public void printName() { System.out.println(name + "——Sub"); } public static void main(String[] args) { new SubClass(); } } When run the code, the output is: null——Sub Sub——Sub while it should be: Base——Base Sub——Sub I wonder why the BaseClass constructor calls the SubClass method, can anybody explain this? Thanks in advance.

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  • how to save state of dynamically created editTexts

    - by user922531
    I'm stuck at how to save the state of my EditTexts on screen orientation. Currently if text is inputted into the EditTexts and the screen is orientated, the fields are wiped (as expected). I am already calling onSaveInstanceState and saving a String, but I have no clue on how to save the EditTexts which are created in code and then retrieve them and add them to the EditTexts when redrawing the activity. Snippet of my code: My main activity is as follows: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); // get the multidim array b = getIntent().getBundleExtra("obj"); m = (Methods) b.getSerializable("Methods"); // method to draw the layout InitialiseUI(); // Restore UI state from the savedInstanceState. if (savedInstanceState != null) { String strValue = savedInstanceState.getString("light"); if (strValue != null) { FLight = strValue; } } try { mCamera = Camera.open(); if (FLight.equals("true")) { flashLight(); } } catch (Exception e) { Log.d(TAG, "Thrown exception onCreate() camera: " + e); } } // end onCreate /** Called when the back button is pressed. */ @Override public void onResume() { super.onResume(); try { mCamera = Camera.open(); if (FLight.equals("true")) { flashLight(); } } catch (Exception e) { Log.d(TAG, "Thrown exception onCreate() camera: " + e); } } // end onCreate /** saves data before leaving the screen */ @Override protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putString("light", FLight); } /** called when exiting / leaving the screen */ @Override protected void onPause() { super.onPause(); Log.d(TAG, "onPause()"); if (mCamera != null) { mCamera.stopPreview(); mCamera.release(); mCamera = null; } } /* * set up the UI elements - add click listeners to buttons used in * onCreate() and onConfigurationChanged() * * Set the editTexts fields to show the previous readings as Hints */ public void InitialiseUI() { Log.d(TAG, "Start of InitialiseUI, Main activity"); // get a reference to the TableLayout final TableLayout myTLreads = (TableLayout) findViewById(R.id.myTLreads); // Create arrays to hold the TVs and ETs final TextView[] myTextViews = new TextView[m.getNoRows()]; // create an empty array; final EditText[] myEditTexts = new EditText[m.getNoRows()]; // create an empty array; for(int i =0; i<=m.getNoRows()-1;i++ ){ TableRow tr=new TableRow(this); tr.setLayoutParams(new LayoutParams( LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT)); // create a new textview / editText final TextView rowTextView = new TextView(this); final EditText rowEditText = new EditText(this); // setWidth is needed otherwise my landscape layout is OFF rowEditText.setWidth(400); // this stops the keyboard taking up the whole screen in landscape layout rowEditText.setImeOptions(EditorInfo.IME_FLAG_NO_EXTRACT_UI); // add some padding to the right of the TV rowTextView.setPadding(0,0,10,0); // set colors to white rowTextView.setTextColor(Color.parseColor("#FFFFFF")); rowEditText.setTextColor(Color.parseColor("#FFFFFF")); // if readings already sent today set color to yellow if(m.getTransmit(i+1)==false){ rowEditText.setEnabled(false); rowEditText.setHintTextColor(Color.parseColor("#FFFF00")); } // set the text of the TV to the meter name rowTextView.setText(m.getMeterName(i+1)); // set the hint of the ET to the last submitted reading rowEditText.setHint(m.getLastReadString(i+1)); // add the textview to the linearlayout rowEditText.setInputType(InputType.TYPE_CLASS_PHONE);//InputType.TYPE_NUMBER_FLAG_DECIMAL); tr.addView(rowTextView); tr.addView(rowEditText); myTLreads.addView(tr); // add a reference to the textView myTextViews[i] = rowTextView; myEditTexts[i] = rowEditText; } final Button submit = (Button) findViewById(R.id.submitReadings); // add a click listener to the button try { submit.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { Log.d(TAG, "Submit button clicked, Main activity"); preSubmitCheck(m.getAccNo(), m.getPostCode(), myEditTexts); // method to do HTML getting and sending } }); } catch (Exception e) { Log.d(TAG, "Exceptions (submit button)" + e.toString()); } }// end of InitialiseUI I don't need to do anything with these values until a button is clicked. Would it be easier if they were a ListView, i'm guessing I would still have the problem of saving them and retrieving them on rotation. If it helps I have an object m which is a string[][] I could temporarily somehow store them in

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  • PropertyGrid + interface

    - by nilphilus
    public interface ITest { void Somethink(); } public class Test1 : ITest { public void Somethink() { /* do stuff */ } public int Test1Property { get; set; } } public class Test2 : ITest { public void Somethink() { /* do stuff */ } public float Test2Property { get; set; } } //Main class public class MainClass { [TypeConverter(ExpandableObjectConverter)] public ITest test { get; set; } } Ok, i have sth like this. Instance of MainClass is selected by PropertyGrid. How to make a DropDownList of objects of classes which implement ITest (here Test1 and Test2)

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  • ASP.NET null reference exception

    - by nanek
    Please help me to figure out what is wrong with this code: I have ASP.NET page with one button visible. When user clicks it - it instances MyClass (its implementation is in AppCode directory) and turns invisible (button2 becomes visible). When I click button2 it raises "Object reference not set to an instance of an object" Exception. What seems to be the problem? { public MyClass noviTest; protected void Page_Load(object sender, EventArgs e) { } protected void Button1_Click(object sender, EventArgs e) { noviTest = new MyClass(TextBox1.Text); Button1.Visible = false; Button2.Visible = true; } protected void Button2_Click(object sender, EventArgs e) { Label1.Text=noviTest.getID; //this is the critical line } } Thank You in advance, Regards

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  • XAML-based applications - Event Naming Conventions for C#

    - by user118190
    For event handling, I am starting to see many coders doing this: XButton.Click += OnXButtonClicked() ... void OnXButtonClicked() { ... } Where did this On_ convention come from? It just doesn't feel right in terms of methods. I am starting to see this as well and am wondering what others thought: XButton.Click += HandleXButtonClick() ... void HandleXButtonClick() { ... } When using intellisense, Visual Studio handles these like so: XButton.Click += XButton_Click; ... void XButton_Click(object sender, RoutedEventArgs e) { ... } I am seeking some advice on these naming conventions and would greatly appreciate some advice.

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  • C++ performance, optimizing compiler, empty function in .cpp

    - by Dodo
    I've a very basic class, name it Basic, used in nearly all other files in a bigger project. In some cases, there needs to be debug output, but in release mode, this should not be enabled and be a NOOP. Currently there is a define in the header, which switches a makro on or off, depending on the setting. So this is definetely a NOOP, when switched off. I'm wondering, if I have the following code, if a compiler (MSVS / gcc) is able to optimize out the function call, so that it is again a NOOP. (By doing that, the switch could be in the .cpp and switching will be much faster, compile/link time wise). --Header-- void printDebug(const Basic* p); class Basic { Basic() { simpleSetupCode; // this should be a NOOP in release, // but constructor could be inlined printDebug(this); } }; --Source-- // PRINT_DEBUG defined somewhere else or here #if PRINT_DEBUG void printDebug(const Basic* p) { // Lengthy debug print } #else void printDebug(const Basic* p) {} #endif

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  • Please see following code and answer

    - by user323422
    template <class T> class _cExplicitInstation { public: void show1(T c) { double d =10.02 ; std::cout<<c; } void show2(T d) { std::cout<<d; } }; template _cExplicitInstation<char>; template void _cExplicitInstation<int>::show1(int c); int main() { _cExplicitInstation<char> abc; _cExplicitInstation<int>().show2(10);// it should show error as i have // explicitly declare for show1() function but its working // can u tell why? }

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  • Google App Engine datastore-primary key

    - by megala
    Hi, I've created a table in the Google App Engine Datastore. It contains the following FIELDS(GROUPNAME,GROUPID,GROUPDESC). How do I set GROUPID as the primary key? My code is as follows: @Entity @Table(name="group" , schema="PUBLIC") public class Creategroup { @Basic private String groupname; @Basic private String groupid; @Basic private String groupdesc; public void setGroupname(String groupname) { this.groupname = groupname; } public String getGroupname() { return groupname; } public void setGroupid(String groupid) { this.groupid = groupid; } public String getGroupid() { return groupid; } public void setGroupdesc(String groupdesc) { this.groupdesc = groupdesc; } public String getGroupdesc() { return groupdesc; } public Creategroup(String groupname, String groupid, String groupdesc ) { // TODO Auto-generated constructor stub this.groupname = groupname; this.groupid = groupid; this.groupdesc = groupdesc; } }

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  • What's the best way to implement a dynamic proxy in C#?

    - by gap
    Hi, I've got a need to create a dynamic proxy in C#. I want this class to wrap another class, and take on it's public interface, forwarding calls for those functions: class MyRootClass { public virtual void Foo() { Console.Out.WriteLine("Foo!"); } } interface ISecondaryInterface { void Bar(); } class Wrapper<T> : ISecondaryInterface where T: MyRootClass { public Wrapper(T otherObj) { } public void Bar() { Console.Out.WriteLine("Bar!"); } } Here's how I want to use it: Wrapper<MyRootClass> wrappedObj = new Wrapper<MyRootClass>(new MyRootClass()); wrappedObj.Bar(); wrappedObj.Foo(); to produce: Bar! Foo! Any ideas? What's the easiest way to do this? What's the best way to do this? Thanks so much.

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  • How I change a variable of a type to another one in C?

    - by drigoSkalWalker
    I want to do it: int main () { bla bla bla void *onetype; switch (USER_INPUT_TYPE) { CASE CONVERT_TO_CHAR: convert onetype VOID TO CHAR >>> HOW??? CASE CONVERT_TO_INT: convert onetype VOID TO INT >>> HOW??? LOT OF CASES... } } Yes, I know type casting, but type casting is a 'temporary' change. So, is there any way to accomplish it in C? EDIT : Stop stop stop! Please, see, what are you doing is type casting, I KNOW THIS, you are creating another variable of the desirable type like int i = (int) onetype, I don't want this, I want something else like onetype = (int) onetype, without recreate them, without allocate another variable. Thanks a lot guys!

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  • Why would you precede the main() function in C with a data type?

    - by Milktrader
    Many are familiar with the hello world program in C #include <stdio.h> main () { printf ("hello world"); return 0; } Why do some precede the main () function with int as in: int main() Also, I've seen the word 'void' entered inside the () as in: int main(void) It seems like extra typing for nothing, but maybe it's a best practice that pays dividends in other situations? Also, why precede main() with an int if you're returning a character string? If anything, one would expect: char main(void) I'm also foggy about why we return 0 at the end of the function.

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  • Java Thread Message Passing

    - by pkulak
    I'm writing an Android app. I have a main method, which creates and runs a new Thread using an anonymous inner Runnable class. The run() method, when it's done, calls a method on it's parent class (in the main thread) that calls notifyDataSetChanged() so that the main thread can redraw the new data. This is causing all kinds of trouble (ViewRoot$CalledFromWrongThreadException). The thing is, this method being called from the worker thread is on the class that's created in the UI thread. Shouldn't that be running on the UI thread? Or am I missing something? Here's some code about what I'm talking about: public class Mealfire extends Activity { @Override public void onCreate(Bundle icicle) { (new Thread() { public void run() { // Do a bunch of slow network stuff. update(); } }).start(); } private void update() { myAdapter.notifyDatasetChanged(); } }

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  • c++ signatures, pointers

    - by coubeatczech
    Hello, what's the difference between these signatures? T * f(T & identifier); T & f(T & identifier); T f(T & identifier); void f(T * identifier); void f(T & identifier); void f(T identifier); I met pointers in c, but the amperstand in function signature is new for me. Can Anyone explain this?

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  • How does ambigous methods are resolved in java ?

    - by Jijoy
    Hi , I do have a question. package org.study.algos; public class Study { public static void main(String[] args) { A a = new A(); a.m1(null); } } class A { public void m1(String s) { System.out.println("String"); System.out.println(s); } public void m1(Object obj) { System.out.println("Object"); System.out.println(obj); } } Here , the output is String null Why JVM resolve the method to one with String arguement ? Thanks in advance J

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  • doubt in Exceptions

    - by Ajay Singh
    class MyException extends Exception { MyException() {} MyException(String msg) { super(msg);} } public class NewException { static void f() throws MyException { System.out.println("throwing exception from f()"); throw new ClassCastException(); } static void g() throws MyException { System.out.println("throwing exception from g()"); throw new MyException("parametrized "); } public static void main(String ...strings ) { try { f(); } catch(MyException e) { e.printStackTrace(System.out); } try { g(); } catch(MyException e) { e.printStackTrace(System.out); } } } In the function f() iam specifying that "MyException " exception will be thrown and actually iam throwing some other exception which has no relation with MyException but still the compiler does not report any complain.Why is it so??

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