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  • `return value' from Constructor Exception in Java?

    - by Lajos Nagy
    Take a look that the following code snippet: A a = null try { a = new A(); } finally { a.foo(); // What happens at this point? } Suppose A's constructor throws a runtime exception. At the marked line, am I always guaranteed to get a NullPointerException, or foo() will get invoked on a half constructed instance?

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  • Call a method of subclass in Java

    - by eyecreate
    If I have a base class Base thing = null; of which there is a subclass class Subclass extends Base and I instigate it as thing = new Subclass how would I call a method that is specifically in Subclass, but not in Base? ex. Base has only method() Subclass has method() and specialMethod() the method specialMethod() is the one I want to call.

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  • Java - How to get current year?

    - by Yatendra Goel
    I want to know the current Date and Time. The code Calendar.getInstance(); represents a date and time of the system on which the program is running and the system date can be wrong. So Is there any way by which I can get correct current date and time irrespective of the date and time of the system on which program is running?

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  • NullPointerException Java help

    - by KP65
    Hello guys. I've been tearing my hair out the past few hours trying to solve this problem. Every time I click on a JButton which should open a JFrame(And it does), i get a stacktrace saying I have a null point exception at these bits of code: In class A i have: aButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { B instanceofB = new B(userSession.getBalance()); }); and Class B super.getSomeBtn().setVisible(false); This is where the stacktrace says the errors are in the two above sections. I have a line exactly the same as the one above in Class B and it works fine? Really stuck here!

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  • JAVA Inheritance Generics and Casting.

    - by James Moore
    Hello, I have two classes which both extends Example. public class ClassA extends Example { public ClassA() { super("a", "class"); } .... } public class ClassB extends Example { public ClassB() { super("b", "class"); } .... } public class Example () { public String get(String x, String y) { return "Hello"; } } So thats all very well. So suppose we have another class called ExampleManager. With example manager I want to use a generic type and consequently return that generic type. e.g. public class ExampleManager<T extends Example> { public T getExample() { return new T("example","example"); // So what exactly goes here? } } So where I am returning my generic type how do i get this to actually work correctly and cast Example as either classA or classB? Many Thanks

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  • Java M4A atom tagging free space issue

    - by Brett
    Hey, I've been trying to be able to read and write iTunes style M4A atoms and while I've successfully done the reading part, I've come to a bit of a halt in regards to the free space atoms. I figured that I should be able edit and shift the padding around to accommodate writing an atom with more data than it originally had. I've been stuck on this for about a day now, and I've been trying to figure out how to determine the closest free space atom with enough size to accommodate the new data. so far I have: private freeAtom acquireFreeSpaceAtom( long position ) { long atomStart = Long.MAX_VALUE; freeAtom atom = null; for( freeAtom a : freeSpace ) { if( Math.abs( position - atomStart ) > Math.abs( position - a.getAtomStart() ) ) atomStart = ( atom = a ).getAtomStart(); } return atom; } That code only takes into account the closest free space atom and completely disregards the fact that it should be greater than or equal to a certain size, but I can't quite figure out how I should check for both closeness and size efficiently.

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  • Java xsd validation of xml without namespace

    - by Darkflare
    Hi, I want to validate an xml file against an xsd schema. The xml files root element does not have any namespace or xsi details. It has no attributes so just . I have tried the following code from http://www.ibm.com/developerworks/xml/library/x-javaxmlvalidapi.html with no luck as I receive cvc-elt.1: Cannot find the declaration of element 'root' SchemaFactory factory = SchemaFactory.newInstance("http://www.w3.org/2001/XMLSchema"); File schemaFile = new File("schema.xsd"); Schema xsdScheme = factory.newSchema(schemaFile); Validator validator = xsdScheme.newValidator(); Source source = new StreamSource(xmlfile); validator.validate(source); The xml validates fine with the namespace headers included etc (added via xmlspy), but I would have thought the xml namespace could be declared without having to manually edit the source file?

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  • Java Refreshing a screen

    - by Goutham
    I have a screen in which one of its components is made invisible depending on a boolean value. If the boolean changes after the screen has been created, how do I refresh the screen to take this into account?

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  • export a JOGL applet and embedd into a html page

    - by nkint
    hi guys it is some time that i'm testing opengl with java and JOGL. now i have good result and i wanto to pubblish it on web. but i have some problem. i'm in eclipse, and i'm testing an Applet with JOGL. first of all i have this run time error (but the program works correctly): java.lang.IllegalArgumentException: adding a window to a container at java.awt.Container.checkNotAWindow(Container.java:431) at java.awt.Container.addImpl(Container.java:1039) at java.awt.Container.add(Container.java:365) at AppletHelloWorld.init(AppletHelloWorld.java:30) at sun.applet.AppletPanel.run(AppletPanel.java:424) at java.lang.Thread.run(Thread.java:619) then i found this incredibly clear page and i do what is said, i open html with the browser, the libs are downloaded but it stops at "Starting applet AppletHelloWorld" that is the name i gave to my applet. mayebe i miss something like main function or exporting well the jar? this is my main code: public class AppletHelloWorld extends Applet { public static void main(String[] args) { JFrame fr=new JFrame(); fr.setBounds(0,0,1015,600); fr.add(new AppletHelloWorld()); fr.setVisible(true); } public void init() { setLayout(null); MyJOGLProject canvas = new MyJOGLProject(); //MyJOGLProject extends JFrame canvas.run(); Container c = new Container(); c.add(canvas); add(c); } //....

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  • Nothing happen when refreshing the main Frame (JAVA)

    - by Ams
    Hello everyone, I try to show a ( Logged in ) message when a user is succefully connected but nothing happen when a do a repaint(). you can take a look to the code : public class MainFrame extends JFrame implements ActionListener{ private static final long serialVersionUID = 1L; private static final int FRAME_HEIGHT = 400; private static final int FRAME_WIDTH = 250; private static final String TITLE = new String("TweeX"); private static String TWITTERID = new String(); private static String TWITTERPW = new String(); private boolean logged = false; private JTextField loginField = new JTextField(10); private JPasswordField passField = new JPasswordField(10); private JButton login = new JButton("Connect"); private GridBagConstraints c = new GridBagConstraints(); private String UserStatus = new String("Please login..."); /* * Constructor ! */ MainFrame() { setSize(FRAME_WIDTH, FRAME_HEIGHT); setTitle(TITLE); setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); setResizable(false); loginUser(); } /* * Login Forms */ protected void loginUser(){ this.setLayout(new GridBagLayout()); //add Login Fiels + Label c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 0; c.insets = new Insets(5,5,5,20); c.gridy = 0; add(new JLabel("Username:"),c); c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 1; c.gridy = 0; add(loginField,c); //add Password Fiels + Label c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 0; c.gridy = 1; add(new JLabel("Password:"),c); c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 1; c.gridy = 1; add(passField,c); //add Login button c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 1; c.gridy = 2; add(login,c); //add listener to login button login.addActionListener((ActionListener) this); c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 1; c.gridy = 3; add(new JLabel(UserStatus),c); setVisible(true); } @Override public void actionPerformed(ActionEvent e) { TWITTERID = loginField.getText(); TWITTERPW = passField.getText(); Twitter twitter = new TwitterFactory().getInstance(TWITTERID,TWITTERPW); logged = true; try { twitter.verifyCredentials(); } catch (TwitterException e1) { logged = false; } } protected void connect(){ if(logged){ UserStatus = "Loged In :)"; repaint(); } } static public void main(String[] argv) { new MainFrame(); } }

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  • Java: autofiltering list?

    - by Jason S
    I have a series of items arriving which are used in one of my data structures, and I need a way to keep track of those items that are retained. interface Item {} class Foo implements Item { ... } class Baz implements Item { ... } class StateManager { List<Foo> fooList; Map<Integer, Baz> bazMap; public List<Item> getItems(); } What I want is that if I do the following: for (int i = 0; i < SOME_LARGE_NUMBER; ++i) { /* randomly do one of the following: * 1) put a new Foo somewhere in the fooList * 2) delete one or more members from the fooList * 3) put a new Baz somewhere in the bazMap * 4) delete one or more members from the bazMap */ } then if I make a call to StateManager.getItems(), I want to return a list of those Foo and Baz items, which are found in the fooList and the bazMap, in the order they were added. Items that were deleted or displaced from fooList and bazMap should not be in the returned list. How could I implement this? SOME_LARGE_NUMBER is large enough that I don't have the memory available to retain all the Foo and Baz items, and then filter them.

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  • Stateful Iterators Java

    - by Gitmo
    What is a Stateful Iterator? This question relates to an Iterator defined in Hadoop for performing Joins. As the reference documentation states: This defines an interface to a stateful Iterator that can replay elements added to it directly. Note that this does not extend Iterator. What does 'replay elements added to it directly' mean? How is this iterator different from a usual iterator?

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  • Java method get the inheriting type

    - by DrDro
    I have several classes that extend C and I would need a method that accepts any argument of type C. But in this method I would like to know if I'm dealing with A or B. * public A extends C public B extends C public void goForIt(C c)() If I cast how can I retrieve the type in a clean way (I just read using getClass or instanceof is often not the best way). PS: Fell free to edit an explicit title. *Sorry but I can't type closing braces

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  • Java io ugly try-finally block

    - by Tom Brito
    Is there a not so ugly way of treat the close() exception to close both streams then: InputStream in = new FileInputStream(inputFileName); OutputStream out = new FileOutputStream(outputFileName); try { copy(in, out); } finally { try { in.close(); } catch (Exception e) { try { // event if in.close fails, need to close the out out.close(); } catch (Exception e2) {} throw e; // and throw the 'in' exception } out.close(); }

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  • Java: Generics, Class.isaAssignableFrom, and type casting

    - by bguiz
    This method that uses method-level generics, that parses the values from a custom POJO, JXlistOfKeyValuePairs (which is exactly that). The only thing is that both the keys and values in JXlistOfKeyValuePairs are Strings. This method wants to taken in, in addition to the JXlistOfKeyValuePairs instance, a Class<T> that defines which data type to convert the values to (assume that only Boolean, Integer and Float are possible). It then outputs a HashMap with the specified type for the values in its entries. This is the code that I have got, and it is obviously broken. private <T extends Object> Map<String, T> fromListOfKeyValuePairs(JXlistOfKeyValuePairs jxval, Class<T> clasz) { Map<String, T> val = new HashMap<String, T>(); List<Entry> jxents = jxval.getEntry(); T value; String str; for (Entry jxent : jxents) { str = jxent.getValue(); value = null; if (clasz.isAssignableFrom(Boolean.class)) { value = (T)(Boolean.parseBoolean(str)); } else if (clasz.isAssignableFrom(Integer.class)) { value = (T)(Integer.parseInt(str)); } else if (clasz.isAssignableFrom(Float.class)) { value = (T)(Float.parseFloat(str)); } else { logger.warn("Unsupporteded value type encountered in key-value pairs, continuing anyway: " + clasz.getName()); } val.put(jxent.getKey(), value); } return val; } This is the bit that I want to solve: if (clasz.isAssignableFrom(Boolean.class)) { value = (T)(Boolean.parseBoolean(str)); } else if (clasz.isAssignableFrom(Integer.class)) { value = (T)(Integer.parseInt(str)); } I get: Inconvertible types required: T found: Boolean Also, if possible, I would like to be able to do this with more elegant code, avoiding Class#isAssignableFrom. Any suggestions? Sample method invocation: Map<String, Boolean> foo = fromListOfKeyValuePairs(bar, Boolean.class);

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  • How do I display java.lang.* object allocations in Eclipse profiler?

    - by Martin Wickman
    I am profiling an application using the Eclipse profiler. I am particularly interested in number of allocated object instances of classes from java.lang (for instance java.lang.String or java.util.HashMap). I also want to know stuff like number of calls to String.equals() etc. I use the "Object Allocations" tab and I shows all classes in my application and a count. It also shows all int[], byte[], long[] etc, but there is no mention of any standard java classes. For instance, this silly code: public static void main(String[] args) { Object obj[] = new Object[1000]; for (int i = 0; i < 1000; i++) { obj[i] = new StringBuffer("foo" + i); } System.out.println (obj[30]); } Shows up in the Object Allocations tab as 7 byte[]s, 4 char[]s and 2 int[]s. It doesn't matter if I use 1000 or 1 iterations. It seems the profiler simply ignores everything that is in any of the java.* packages. The same applies to Execution Statistics as well. Any idea how to display instances of java.* in the Eclipse Profiler?

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  • Java String.split

    - by user903772
    I have the following text: ARIYALUR:ARIYALUR|CHENNAI:CHENNAI|COIMBATORE:COIMBATORE|CUDDALORE:CUDDALORE|DINDIGUL:DINDIGUL|ERODE:ERODE|KANCHEEPURAM:KANCHEEPURAM|KANYAKUMARI:KANYAKUMARI|KRISHNAGIRI:KRISHNAGIRI|MADURAI:MADURAI|NAMAKKAL:NAMAKKAL|NILGIRIS:NILGIRIS|PERAMBALUR:PERAMBALUR|PONDICHERRY:PONDICHERRY|SALEM:SALEM|THANJAVUR:THANJAVUR|THENI:THENI|THIRUVALLUR:THIRUVALLUR|THOOTHUKUDI:THOOTHUKUDI|TIRUNELVELI:TIRUNELVELI|VELLORE:VELLORE|VILLUPURAM:VILLUPURAM|VIRUDHUNAGAR:VIRUDHUNAGAR| I tried to do a split("|") but my array is made up of alphabets and not each district. Please help.

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  • How to place images on top of each other in java

    - by Haxed
    Hi, I have a background image of a road, which I have displayed on a JFrame using an ImageIcon. I want to put a car on top of that background image at a certain (x,y) location. I tried using another ImageIcon and the background does not appear when I run the program , however the car does. import javax.swing.ImageIcon; import javax.swing.JFrame; import javax.swing.JLabel; public class Gui extends JFrame { private ImageIcon northcar = new ImageIcon("src/north.gif"); private ImageIcon usIcon = new ImageIcon("src/trafficLight.jpg"); public Gui() { add(new JLabel(usIcon)); // background image does not appear after the i added the northcar label add(new JLabel(northcar)); // this picture can be seen } public static void main(String[] args) { Gui frame = new Gui(); frame.setTitle("TestImageIcon"); frame.setLocationRelativeTo(null); // Center the frame frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setBounds(0, 0, 650, 650); frame.setVisible(true); } } I heard about using a canvas but have no clue. Any ideas ? Many Thanks

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  • JADE (Java) - Changing Agent Container

    - by Chad S
    Is there a way to reassign agents to a different container or will I have to create a new container and then create all new instances of the agents within the new container? I have done a lot of searching and can't seem to find anything on container reassignment. Thanks in advance for any info!

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  • Java apache commons library source license question

    - by llm
    I want to use functionality from a certain method in apache commons StringUtils. I currently do not have the option of just using the library as one would normally do. I found the source for the method I need and my question is: am I free (legally) to use this code (just a method out of the library) or do I have to use the entire library? If its ok, what kind of attribution would I need in my code, if any? Thanks.

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  • Issue with Java join() method.

    - by gmunk
    First of all here are some code snippets: http://pastebin.com/9ZCwekXs http://pastebin.com/TtLLXPYP I'm trying to animate some images. The thing is that I want the main thread to wait for the animation thread to finish and then to continue. I searched around, read a little bit and decided to use the join() method. It perfectly waits for the thread to finish but I doesn't animate correctly. The repaint() method gets called 2 times instead of nine. I think maybe the problem is because I used singletons. Here is the singleton implementation. http://pastebin.com/bA3qLZJE

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  • Sending an Email Using Java

    - by user217029
    try{ Properties props = new Properties(); props.put("mail.smtp.host", "ipc-smtp.bits-pilani.ac.in"); Session sess = Session.getInstance(props, null); sess.setDebug(true); Message msg = new MimeMessage(sess); InternetAddress addressFrom = new InternetAddress("[email protected]"); msg.setFrom(addressFrom); msg.setRecipient(Message.RecipientType.TO, new InternetAddress("[email protected]")); msg.addHeader("MyHeaderName", "myHeaderValue"); msg.setSubject("Test"); msg.setContent("Yippe", "text/plain"); Transport.send(msg); }catch(Exception exp){ exp.printStackTrace(); } The error is javax.mail.MessagingException: 554 The mail was blocked due to zen-spamhaus RBL action This is my college's smtp server.

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  • Lines don't overlap when they should Java Swing

    - by Sven
    I'm drawing lines in a JFrame on a self made gridPanel. Problem is, I draw the lines between 2 points. When I have a line that is between point 1 and point 2 and a line between point 2 and point 3, the lines should connect. This however isn,t the case, there is a small gap in between, no idea why. But it isn't drawing till the end of the specified point. (start point is correct.) Here is the code of the JFrame: public void initialize(){ this.setLayout(new BorderLayout()); this.setPreferredSize(new Dimension(500, 400)); gridPane = new GridPane(); gridPane.setBackground(Color.WHITE); gridPane.setSize(this.getPreferredSize()); gridPane.setLocation(0, 0); this.add(gridPane,BorderLayout.CENTER); //createSampleLabyrinth(); drawWall(0,5,40,5); //These are the 2 lines that don't connect. drawWall(40,5,80,5); this.pack(); } drawWall calls a method that calls a method in GridPane. The relevant code in gridPane: /** * Draws a wall on this pane. With the starting point being x1, y1 and its end x2,y2. * @param x1 * @param y1 * @param x2 * @param y2 */ public void drawWall(int x1, int y1, int x2, int y2) { Wall wall = new Wall(x1,y1,x2,y2, true); wall.drawGraphic(); wall.setLocation(x1, y1); wall.setSize(10000,10000); this.add(wall, JLayeredPane.DEFAULT_LAYER); this.repaint(); } This method creates a wall and puts it in the Jframe. The relevant code of the wall: public class Wall extends JPanel { private int x1; private int x2; private int y1; private int y2; private boolean black; /** * x1,y1 is the start point of the wall (line) end is x2,y2 * * @param x1 * @param y1 * @param x2 * @param y2 */ public Wall(int x1, int y1, int x2, int y2, boolean black) { this.x1 = x1; this.x2 = x2; this.y1 = y1; this.y2 = y2; this.black = black; setOpaque(false); } private static final long serialVersionUID = 1L; public void drawGraphic() { repaint(); } public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2 = (Graphics2D) g; if(black){ g2.setColor(Color.BLACK); g2.setStroke(new BasicStroke(8)); } else { g2.setColor(Color.YELLOW); g2.setStroke(new BasicStroke(3)); } g2.drawLine(x1, y1, x2, y2); } } So, where am I going wrong? The true/false is to determine if the wall should be black or yellow, nothing to be concerned about.

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  • Java Data Structure

    - by Joe
    Hi there, I'm looking for a data structure that will act like a Queue so that I can hava First In First Out behaviour, but ideally I would also be able to see if an element exists in that Queue in constant time as you can do with a HashMap, rather than the linear time that you get with a LinkedList. I thought a LinkedHashMap might do the job, but although I could make an iterator and just take and then remove the first element of the iteration to produce a sort of poll() method, I'm wondering if there is a better way. Many thanks in advance

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  • How to mix two arrays in Java?

    - by roddik
    Hello. I have some String[] arrays, for example: ['a1', 'a2'] ['b1', 'b2', 'b3', 'b4'] ['c1'] How can I mix them, so that I get ['a1', 'b1', 'c1', 'a2', 'b2', 'b3', 'b4'] (0 element of a, then b, c, 1 element of a, b, c and so on)? Thanks

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