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  • java.lang.UnsupportedClassVersionError: Bad version number in .class file?

    - by grmn.bob
    I am getting this error when I include an opensource library that I had to compile from source. Now, all the suggestions on the web indicate that the code was compiled in one version and executed in another version (new on old). However, I only have one version of JRE on my system. If I run the commands: $ javac -version javac 1.5.0_18 $ java -version java version "1.5.0_18" Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_18-b02) Java HotSpot(TM) Server VM (build 1.5.0_18-b02, mixed mode) and check in Eclipse for the properties of the java library, I get 1.5.0_18 Therefore, I have to conclude something else, internal to a class itself, is throwing the exception?? Is that even possible?

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  • .NET developer has a few hours to cram for a Java proficiency test. What to do?

    - by Paul Sasik
    I have an interview tomorrow morning and just found out that I will also be taking an hour-long Java proficiency test! I am a certified C# .NET developer but have barely touched Java since college. (Yes, I am thinking about switching from .NET development to Java!) I'm not going to be able to effectively cram the whole of the Java library by tomorrow morning. What are some key ideas that I should study that might actually make a difference in such a short time frame? (The examiners will be taking into account that I have had little exposure to Java.) Thanks! Edit NOTE: I think that the exam is going to be written, so no specific IDE.

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  • How do you convert date taken from a bash script to milliseconds in a Java program?

    - by Matt Pascoe
    I am writing a piece of code in Java that needs to take a time sent from a bash script and parse the time to milliseconds. When I check the millisecond conversion on the date everything is correct except for the month I have sent which is January instead of March. Here is the variable I create in the bash script, which later in the script I pass to the Java program: TIME=`date +%m%d%Y_%H:%M:%S` Here is the Java code which parses the time to milliseconds: String dt = "${scriptstart}"; java.text.SimpleDateFormat scriptStart = new java.text.SimpleDateFormat("MMDDyyyy_HH:mm:ss"); long start = scriptStart.parse(dt).getTime(); The goal of this statement is to find the elapsed time between the start of the script and the current system time. To troubleshoot this I printed out the two: System Time = 1269898069496 (converted = Mon Mar 29 2010 16:27:49 GMT-0500 (Central Daylight Time)) Script Start = 03292010_16:27:45 Script Start in Milli = 1264804065000 (Converted = Fri Jan 29 2010 16:27:45 GMT-0600 (Central Standard Time))

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  • Java MVC - How to divide a done text game into MVC?

    - by Zopyrus
    Been sitting here for hours now trying to figure this out, so a bit sympathy for this large question. :) The Goal: I simply want to divide my done code into MVC (Model View Controller) parts. I have the game logics done and text based - the code works fine. The Problem: Well, I want to implement this code into MVC, but where do explain for the MODEL that it should use text-based? Because the VIEW is only for the layout (graphically) correct? I am having a REALLY hard time figuring out where to begin at all. Any pointers would be so nice! Here is my game logics code: import mind.*; import javax.swing.*; import java.util.*; import java.lang.*; import java.awt.*; public class Drive { String[] mellan; boolean gameEnd, checkempty, checkempty2, enemy, enemy2; String gr,rd,tom; int digits; public Drive() { // Gamepieces in textform gr="G"; rd="R"; tom=" "; mellan = new String[7]; String[] begin = {gr,gr,gr,tom,rd,rd,rd}; String[] end = {rd,rd,rd,tom,gr,gr,gr}; //input Scanner in = new Scanner(System.in); mellan=begin; gameEnd=false; while (gameEnd == false) { for(int i=0; i<mellan.length; i++) { System.out.print(mellan[i]); } System.out.print(" Choose 0-6: "); digits = in.nextInt(); move(); checkWin(); } } void move() { //BOOLEAN for gameruls!!! checkempty = digits<6 && mellan[digits+1]==tom; checkempty2 = digits>0 && mellan[digits-1]==tom; enemy = (mellan[digits]==gr && mellan[digits+1]==rd && mellan[digits+2]==tom); enemy2 = (mellan[digits]==rd && mellan[digits-1]==gr && mellan[digits-2]==tom); if(checkempty) { mellan[digits+1]=mellan[digits]; mellan[digits]=tom; } else if (checkempty2) { mellan[digits-1]=mellan[digits]; mellan[digits]=tom; } else if (enemy) { mellan[digits+2]=mellan[digits]; mellan[digits]=tom; } else if (enemy2) { mellan[digits-2]=mellan[digits]; mellan[digits]=tom; } } void checkWin() { String[] end = {rd,rd,rd,tom,gr,gr,gr}; for (int i=0; i<mellan.length; i++){ } if (Arrays.equals(mellan,end)) { for (int j=0; j<mellan.length; j++) { System.out.print(mellan[j]); } displayWin(); } } void displayWin() { gameEnd = true; System.out.println("\nNicely Done!"); return; } // Kör Drive! public static void main(String args[]) { new Drive(); } } Here is how I defined my DriveView thus far: (just trying to make one button to work) import mind.*; import javax.swing.*; import java.util.*; import java.lang.*; import java.awt.*; import java.awt.event.*; public class DriveView extends JFrame { JButton ruta1 = new JButton("Green"); JButton ruta2 = new JButton("Green"); JButton rutatom = new JButton(""); JButton ruta6 = new JButton("Red"); private DriveModel m_model; public DriveView(DriveModel model) { m_model = model; //Layout for View JPanel myPanel = new JPanel(); myPanel.setLayout(new FlowLayout()); myPanel.add(ruta1); myPanel.add(ruta2); myPanel.add(rutatom); myPanel.add(ruta6); this.setContentPane(myPanel); this.pack(); this.setTitle("Drive"); this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } void addMouseListener(ActionListener mol) { ruta2.addActionListener(mol); } } And DriveController which gives me error at compile import mind.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.lang.*; public class DriveController { private DriveModel m_model; private DriveView m_view; public DriveController(DriveModel model, DriveView view) { m_model = model; m_view = view; view.addMouseListener(new MouseListener()); } class MouseListener implements ActionListener { public void actionPerformed(ActionEvent e) { String mening; mening = e.getActionCommand(); if (mening.equals("Green")) { setForeground(Color.red); } } } }

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  • How can I stub out a call to super in a imported Java class in JRuby for testing

    - by Doug Chew
    I am testing Java classes with RSpec and JRuby. How can I stub out a call to super in an imported Java class in my RSpec test? For example: I have 2 Java classes: public class A{ public String foo() { return "bar"; } } public class B extends A public String foo() { // B code return super.foo(); } } I am just trying to test the code in B.foo and not the code in A.foo with JRuby. How can I stub out the call to the super class method in my RSpec test? rspec test: java_import Java::B describe B do it "should not call A.foo" do # some code to stub out A.foo b = B.new b.foo.should_not == "bar" end end I have tried including a module with a new foo method in B's class hoping that it would hit the module method first but B still makes a call to A. The inserting module technique works in Ruby but not with JRuby and imported Java classes. Any other ideas to stub out the superclass method to get my RSpec test to pass?

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  • Java: how does isDirectory and isFile work in File-class?

    - by HH
    $ javac GetAllDirs.java GetAllDirs.java:16: cannot find symbol symbol : variable checkFile location: class GetAllDirs System.out.println(checkFile.getName()); ^ 1 error $ cat GetAllDirs.java import java.util.*; import java.io.*; public class GetAllDirs { public void getAllDirs(File file) { if(file.isDirectory()){ System.out.println(file.getName()); File checkFile = new File(file.getCanonicalPath()); }else if(file.isFile()){ System.out.println(file.getName()); File checkFile = new File(file.getParent()); }else{ // checkFile should get Initialized at least HERE! File checkFile = file; } System.out.println(file.getName()); // WHY ERROR HERE: checkfile not found System.out.println(checkFile.getName()); } public static void main(String[] args) { GetAllDirs dirs = new GetAllDirs(); File current = new File("."); dirs.getAllDirs(current); } }

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  • Java: how to initialize private final int value with if-else in constructor?

    - by HH
    $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; InitInt(){} public static void main(String[] args) { // I don't want to assign any value. // just initialize it, how? InitInt test = new InitInt(); System.out.println(test.getRight()); // later assiging a value } public int getRight(){return right;} } Initialization problem with Constructor, due to if-else -loop InitInt{ // Still the error, "may not be initialized" // How to initialise it, without removing if-else? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } }

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  • how to run/compile java code from JTextArea at Runtime? ----urgent!!! college project

    - by Lokesh Kumar
    I have a JInternalFrame painted with a BufferedImage and contained in the JDesktopPane of a JFrame.I also have a JTextArea where i want to write some java code (function) that takes the current JInternalFrame's painted BufferedImage as an input and after doing some manipulation on this input it returns another manipulated BufferedImage that paints the JInternalFrame with new manipulated Image again!!. Manipulation java code of JTextArea:- public BufferedImage customOperation(BufferedImage CurrentInputImg) { Color colOld; Color colNew; BufferedImage manipulated=new BufferedImage(CurrentInputImg.getWidth(),CurrentInputImg.getHeight(),BufferedImage.TYPE_INT_ARGB); //make all Red pixels of current image black for(int i=0;i< CurrentInputImg.getWidth();i++) { for(int j=0;j< CurrentInputImg.getHeight(),j++) { colOld=new Color(CurrentInputImg.getRGB(i,j)); colNew=new Color(0,colOld.getGreen(),colOld.getBlue(),colOld.getAlpha()); manipulated.setRGB(i,j,colNew.getRGB()); } } return manipulated; } so,how can i run/compile this JTextArea java code at runtime and get a new manipulated image for painting on JInternalFrame???????   Here is my Main class: (This class is not actual one but i have created it for u for basic interfacing containing JTextArea,JInternalFrame,Apply Button) import java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.event.*; import javax.swing.JInternalFrame; import javax.swing.JDesktopPane; import java.awt.image.*; import javax.imageio.*; import java.io.*; import java.io.File; import java.util.*; class MyCustomOperationSystem extends JFrame **{** public JInternalFrame ImageFrame; public BufferedImage CurrenFrameImage; public MyCustomOperationSystem() **{** setTitle("My Custom Image Operations"); setSize((int)Toolkit.getDefaultToolkit().getScreenSize().getWidth(),(int)Toolkit.getDefaultToolkit().getScreenSize().getHeight()); JDesktopPane desktop=new JDesktopPane(); desktop.setPreferredSize(new Dimension((int)Toolkit.getDefaultToolkit().getScreenSize().getWidth(),(int)Toolkit.getDefaultToolkit().getScreenSize().getHeight())); try{ CurrenFrameImage=ImageIO.read(new File("c:/Lokesh.png")); }catch(Exception exp) { System.out.println("Error in Loading Image"); } ImageFrame=new JInternalFrame("Image Frame",true,true,false,true); ImageFrame.setMinimumSize(new Dimension(CurrenFrameImage.getWidth()+10,CurrenFrameImage.getHeight()+10)); ImageFrame.getContentPane().add(CreateImagePanel()); ImageFrame.setLayer(1); ImageFrame.setLocation(100,100); ImageFrame.setVisible(true); desktop.setOpaque(true); desktop.setBackground(Color.darkGray); desktop.add(ImageFrame); this.getContentPane().setLayout(new BorderLayout()); this.getContentPane().add("Center",desktop); this.getContentPane().add("South",ControlPanel()); pack(); setVisible(true); **}** public JPanel CreateImagePanel(){ JPanel tempPanel=new JPanel(){ public void paintComponent(Graphics g) { g.drawImage(CurrenFrameImage,0,0,this); } }; tempPanel.setPreferredSize(new Dimension(CurrenFrameImage.getWidth(),CurrenFrameImage.getHeight())); return tempPanel; } public JPanel ControlPanel(){ JPanel controlPan=new JPanel(new FlowLayout(FlowLayout.LEFT)); JButton customOP=new JButton("Custom Operation"); customOP.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent evnt){ JFrame CodeFrame=new JFrame("Write your Code Here"); JTextArea codeArea=new JTextArea("Your Java Code Here",100,70); JScrollPane codeScrollPan=new JScrollPane(codeArea,ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS); CodeFrame.add(codeScrollPan); CodeFrame.setVisible(true); } }); JButton Apply=new JButton("Apply Code"); Apply.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent event){ // What should I do!!! Here!!!!!!!!!!!!!!! } }); controlPan.add(customOP); controlPan.add(Apply); return controlPan; } public static void main(String s[]) { new MyCustomOperationSystem(); } } Note: in above class JInternalFrame (ImageFrame) is not visible even i have declared it visible. so, ImageFrame is not visible while compiling and running above class. U have to identify this problem before running it.

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  • What is the C# equivalent of java.util.regex?

    - by peter.murray.rust
    I am converting Java code to C# and need to replace the use of Java's regex. A typical use is import java.util.regex.Matcher; import java.util.regex.Pattern; //... String myString = "B12"; Pattern pattern = Pattern.compile("[A-Za-z](\\d+)"); Matcher matcher = Pattern.matcher(myString); String serial = (matcher.matches()) ? matcher.group(1) : null; which should extract a capture group from a matched target string. I'd be grateful for simple examples. EDIT: I have now added the C# equivalent of the code as an answer. EDIT: Here is a tutorial on the use of the actual expressions. EDIT: Here is a useful comparison of C# and Java (and Perl.)

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  • An equivalent of -javaagent in C#? Or: ways to use a java framework in C#.

    - by Alix
    Hi everyone. This is probably something I should be able to figure out by myself, but I'm not having much luck so I figured I'd ask. The issue: I'm translating a system from java to C# and they use a java framework that I'd really like to use, since it takes care of the most complex parts of the system, which I would otherwise have to implement myself. I have the source code of this framework. I know there are several possibilities for using java libraries in C# (although I'm not familiar with any of them, so I'd appreciate suggestions). So far I've thought of using IKVM.NET to generate a .dll, but I'm not sure what to do next, because in java in order to run the framework with your code you're supposed to use the option -javaagent by adding -javaagent:bin/deuceAgent.jar (where deuceAgent is the framework) to your java command line. I don't know what the equivalent in C# would be once I have my .dll, or whether there's an equivalent at all. Any help? Thanks so much.

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  • Correct way to (re)launch a Java application with hardware-dependent VM parameters?

    - by LowLevelAbstraction
    EDIT I don't want to use Java Web Start I've got a Java application that I'd like to run with different VM parameters depending on the amount of memory the system it is launched on has. For example if the machine has 1 GB of memory or less I'd like to pass "-Xmx200m" and "-Xmx400m" if it has 2 GB and "-Xmx800m" if it has 8 GB (these are just examples). Is there a portable way to do this? I've tried having a first tiny Java app (hence portable) that determines the amount of memory available and then launches a new Java app but I don't think this is very clean. As of now I've written Bash shell scripts that invoke the Java app with the correct parameters depending on the config but it only works on Linux on OS X. What is the correct way to solve this? Would application packager package ;) help ?

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  • Testing for interface implementation in WCF/SOA

    - by rabidpebble
    I have a reporting service that implements a number of reports. Each report requires certain parameters. Groups of logically related parameters are placed in an interface, which the report then implements: [ServiceContract] [ServiceKnownType(typeof(ExampleReport))] public interface IService1 { [OperationContract] void Process(IReport report); } public interface IReport { string PrintedBy { get; set; } } public interface IApplicableDateRangeParameter { DateTime StartDate { get; set; } DateTime EndDate { get; set; } } [DataContract] public abstract class Report : IReport { [DataMember] public string PrintedBy { get; set; } } [DataContract] public class ExampleReport : Report, IApplicableDateRangeParameter { [DataMember] public DateTime StartDate { get; set; } [DataMember] public DateTime EndDate { get; set; } } The problem is that the WCF DataContractSerializer does not expose these interfaces in my client library, thus I can't write the generic report generating front-end that I plan to. Can WCF expose these interfaces, or is this a limitation of the serializer? If the latter case, then what is the canonical approach to this OO pattern? I've looked into NetDataContractSerializer but it doesn't seem to be an officially supported implementation (which means it's not an option in my project). Currently I've resigned myself to including the interfaces in a library that is common between the service and the client application, but this seems like an unnecessary extra dependency to me. Surely there is a more straightforward way to do this? I was under the impression that WCF was supposed to replace .NET remoting; checking if an object implements an interface seems to be one of the most basic features required of a remoting interface?

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  • How do you access URL text following the # sign through Java?

    - by cmcculloh
    Using Java (.jsp or whatever) is there a way where I can send a request for this page: http://www.mystore.com/store/shelf.jsp?category=mens#page=2 and have the Java code parse the URL and see the #page=2 and respond accordingly? Basically, I'm looking for the Java code that allows me to access the characters following the hash tag. The reason I'm doing this is that I want to load subsequent pages via AJAX (on my shelf) and then allow the user to copy and paste the URL and send it to a friend. Without the ability of Java being able to read the characters following the hash tag I'm uncertain as to how I would manipulate the URL with Javascript in a way that the server would be able to also read without causing the page to re-load. I'm having trouble even figuring out how to access/see the entire URL (http://www.mystore.com/store/shelf.jsp?category=mens#page=2) from within my Java code...

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  • In MATLAB can I convert a java boolean to a MATLAB logical?

    - by Adrian
    In MATLAB I'm using a couple of java routines I've written to interface with a MyQSL database. One routine returns a boolean value result <1x1 java.lang.Boolean> >> result result = true When I then use it in a conditional statement I get an error message. >> if result, disp('result is true') end ??? Conversion to logical from java.lang.Boolean is not possible. Is there a way to use the java boolean class as a MATLAB logical type? Or do I have to resort to returning integer values from my java routines?

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  • Should class IOException in Java have been an unchecked RuntimeException?

    - by Derek Mahar
    Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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  • What benefits can Java developer have from moving to a *NIX platform?

    - by dave-keiture
    Hi everyone, A friend of mine is a Java developer, who's using *NIX for ages. He claims that *NIX is for real Java geeks, whereas WIN is for dummies (and I'm one of them, according to him) and girls. When I ask him to argue his position, and explain, what's so good for Java developer on *NIX, he starts talking about console, wget, curl and grep. But sorry, wget and curl analogues exist for the WIN platform as well. As for the console - I'm using FAR Commander, and have access to the command line when I need. Moreover, even if I decide moving to *NIX, I will certainly use Netbeans or Eclipse on it, so there will be no big difference. Guys, who use Java on *NIX, could you please give me some real killer examples, when *NIX (any util or technique) dramatically increases Java development productivity (in the way the hints are given in "The Pragmatic Programmer"), or, which is also important, gives more fun from the process. Thanks in advance!

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  • What benefits can Java developer have moving to a *NIX platform?

    - by dave-keiture
    Hi everyone, A friend of mine is a Java developer, who's using *NIX for ages. He claims that *NIX is for real Java geeks, whereas WIN is for dummies (and I'm one of them, according to him) and girls. When I ask him to argue his position, and explain, what's so good for Java developer on *NIX, he starts talking about console, wget, curl and grep. But sorry, wget and curl analogues exist for the WIN platform as well. As for the console - I'm using FAR Commander, and have access to the command line when I need. Moreover, even if I decide moving to *NIX, I will certainly use Netbeans or Eclipse there, so there will be no big difference. Guys, who use Java on *NIX, could you please give me a real killer examples, when *NIX (any util or technique) dramatically increases Java development productivity (in the way the hints are given in "The Pragmatic Programmer"), or, which is also important, gives more fun from the process. Thanks in advance!

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  • How can I do block-oriented disk I/O with Java? Or similar for a B+ tree

    - by Sanoj
    I would like to implement an B+ tree in Java and try to optimize it for disk based I/O. Is there an API for accessing individual disk blocks from Java? or is there an API that can do similar block-oriented access that fits my purpose? I would like to create something like Tokyo Cabinet in 100% Java. Is there anyone that knows what Java only databases like JavaDB is using in the back-end for this? I know that there are probably other languages than Java that can do this better, but I do this in a learning purpose only.

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  • Editing/Modifying a .java file programmatically? (not the .class file)

    - by Jay
    So, here is a piece of code using CodeModel that generates java code: JCodeModel cm = new JCodeModel(); JDefinedClass dc = cm._class("foo.Bar"); JMethod m = dc.method(0, int.class, "foo"); m.body()._return(JExpr.lit(5)); File f = new File("C:/target/classes"); f.mkdirs(); cm.build(f); This code generates a .java file: package foo; public class Bar { int foo() { return 5; } } However, I DO NOT want CodeModel to create a new java file for me. I do have a .java file already and would like to add a few lines of code to a method inside it. So, I would like the API to modify the java file directly/ create a modified copy of it. Is there a way to doing this?

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  • How do you convert date taken from a bash script to milliseconds in java program?

    - by Matt Pascoe
    I am writing a piece of code in java that needs to take a time sent from a bash script and parse the time to milliseconds. When I check the millisecond conversion on the date everything is correct except for the month I have sent which is January instead of March. Here is the variable I create in the bash script, which later in the script I pass to the java program: TIME=`date +%m%d%Y_%H:%M:%S` Here is the java code which parses the time to milliseconds: String dt = "${scriptstart}"; java.text.SimpleDateFormat scriptStart = new java.text.SimpleDateFormat("MMDDyyyy_HH:mm:ss"); long start = scriptStart.parse(dt).getTime(); The goal of this statement is to find the elapsed time between the start of the script and the current system time. To troubleshoot this I printed out the two: System Time = 1269898069496 (converted = Mon Mar 29 2010 16:27:49 GMT-0500 (Central Daylight Time)) Script Start = 03292010_16:27:45 Script Start in Milli = 1264804065000 (Converted = Fri Jan 29 2010 16:27:45 GMT-0600 (Central Standard Time))

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  • In Java how instance of and type cast(i.e (ClassName)) works on proxy object ?

    - by learner
    Java generates a proxy class for a given interface and provides the instance of the proxy class. But when we type cast the proxy object to our specific Object, how java handles this internally? Is this treated as special scenario? For example I have class 'OriginalClass' and it implements 'OriginalInterface', when I create proxy object by passing 'OriginalInterface' interface java created proxy class 'ProxyClass' using methods in the provided interface and provides object of this class(i.e ProxyClass). If my understanding is correct then can you please answer following queries 1) When I type cast object of ProxyClass to my class OriginalClass this works, but how java is allowing this? Same in case of instace of? 2) As my knowledge java creates a proxy class only with the methods, but what happen when I try to access attributes on this object? 3) Only interface methods are getting implemented in Proxy, but what happens when I try to access a method which not in interface and only mentioned in the class? Thanks, Student

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  • How to get the field name of a java (weak) reference pointing to an object in an other class?

    - by Tom
    Imagine I have the following situation: Test1.java import java.lang.ref.WeakReference; public class Test1 { public WeakReference fieldName; public init() { fieldName = new WeakReference(this); Test2.setWeakRef(fieldName); } } Test2.java import java.lang.ref.WeakReference; public class Test2 { public static setWeakRef(WeakReference weakRef) { //at this point I got weakRef in an other class.. now, how do I get the field name this reference was created with? So that it returns exactly "fieldName", because that's the name I gave it in Test1.java? } } At the location of the comment I received the weak reference created in an other class. How would I retreive the field name that this weak reference was created with, in this case "fieldName"? Thanks in advance.

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  • What features of Scala cannot be translated to Java?

    - by Paul
    The Scala compiler compiles direct to Java byte code (or .NET CIL). Some of the features of Scala could be re-done in Java straightforwardly (e.g. simple for comprehensions, classes, translating anonymous/inner functionc etc). What are the features that cannot be translated that way? That is presumably mostly of academic interest. More usefully, perhaps, what are the key features or idioms of Scala that YOU use that cannot be easily represented in Java? Are there any the other way about? Things that can be done straightforwardly in Java that have no straightforward equivalent in Scala? Idioms in Java that don't translate?

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  • Aside from performance concerns, is Java still chosen over Groovy/JRuby etc.?

    - by yar
    [This is an empirical question about the state-of-the-art: I am NOT asking if Java is cooler or less cool than the dynamic languages that work in the JVM.] Aside from cases where performance is a main decision factor, do companies/developers still willingly chose Java over Groovy, JRuby or JPython? Personal Note: The reason I am asking is that, while I do some subset of my professional work in Ruby (not JRuby, for now), in my personal projects I use Java. While I have written non-trivial apps in Groovy, I prefer Java, but I wonder if I should just get over it and do everything in Groovy. I like Java because I feel that static typing saves me time and aids refactoring. (No, I am not familiar with Scala.) However, I feel that this very empirical, on-topic programming question may inform my decision.

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  • How much Java should I have learnt before trying Android programming?

    - by Sidney Yin
    Hi - I have been seeking beginner learning books in Android, and of course found out that I should learn Java first. So I began studying Java and now I am quite comfortable with objects, classes, inheritance, interfaces, and just moved onto Layouts in Swing as well as Swing Features. But I am starting to wonder.... do I know enough about Java now? Can I start programming Android yet? Of course I can keep going in Java, but have been itching to begin programming Android apps. Any definitive answer here about how much Java I need to know before Android? Thanks so much!

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