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  • using Inheritence with GUI (graphical user interfaces) in Java

    - by maya
    hi everyone, I work on inheritence with GUI (graphical user interfaces) let me explain for example I made super class which is vehicle and the subclass is car, so the code to make inheritence will be public class Car extends Vehicle then I want to build the class Car as JFrame like public class Car JFrame implements ActionListener { so the problem is that I couldn't put both codes in the same class, and I need to do that. anyone help me. thanks in advance I wish that the question would be clear

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  • Google App-Engine Java Batch Update

    - by Manjoor
    I need to upload a .csv file and save the records in bigtable. My application successfully parse 200 the records in the csv files and save to table. Here is my code to save the data. for (int i=0;i<lines.length -1;i++) //lines hold total records in csv file { String line = lines[i]; //The record have 3 columns integer,integer,Text if(line.length() > 15) { int n = line.indexOf(","); if (n>0) { int ID = lInteger.parseInt(ine.substring(0,n)); int n1 = line.indexOf(",", n + 2); if(n1 > n) { int Col1 = Integer.parseInt(line.substring(n + 1, n1)); String Col2 = line.substring(n1 + 1); myTable uu = new myTable(); uu.setId(ID); uu.setCol1(MobNo); Text t = new Text(Col2); uu.setCol2(t); PersistenceManager pm = PMF.get().getPersistenceManager(); pm.makePersistent(uu); pm.close(); } } } } But when no of records grow it gives timeout error. The csv file may have upto 800 records. Is it possible to do that in App-Engine? (something like batch update)

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  • Check a Date is between two dates in Java

    - by dimitar
    Hello guys, One thing I want to know is how to calculate what date will it be 10 days from today. Second thing is to check if one Date is between two other Dates. For example, let's say I have an app that shows what events I need to do in the next 10 days (planner). Now how can I see if the date I assigned to an event is between today and the date that is 10 days from today?

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  • Java: when to use static methods

    - by KP65
    Hello, I am wondering when to use static methods? Say If i have a class with a few getters and setters, a method or two, and i want those methods only to be invokable on an instance object of the class. Does this mean i should use a static method? e.g Obj x = new Obj(); x.someMethod or Obj.someMethod (is this the static way?) I'm rather confused!

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  • Is an ArrayList automaticaly declared static ,if it is an instance variable?(Java)

    - by Alex
    Hy ,what i`m trying to do is something like this: private class aClass { private ArrayList idProd; aClass(ArrayList prd) { this.idProd=new ArrayList(prd); } public ArrayList getIdProd() { return this.idProd; } } So if i have multiple instances of ArrayLIst (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); }why all of the aClass objects will return st3 if I access the method getIdProd() for each of them(obj1..obj3)? is an arraylist as a instance variable automatically declared static?

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  • Load/Store Objects in file in Java

    - by brain_damage
    I want to store an object from my class in file, and after that to be able to load the object from this file. But somewhere I am making a mistake(s) and cannot figure out where. May I receive some help? public class GameManagerSystem implements GameManager, Serializable { private static final long serialVersionUID = -5966618586666474164L; HashMap<Game, GameStatus> games; HashMap<Ticket, ArrayList<Object>> baggage; HashSet<Ticket> bookedTickets; Place place; public GameManagerSystem(Place place) { super(); this.games = new HashMap<Game, GameStatus>(); this.baggage = new HashMap<Ticket, ArrayList<Object>>(); this.bookedTickets = new HashSet<Ticket>(); this.place = place; } public static GameManager createManagerSystem(Game at) { return new GameManagerSystem(at); } public boolean store(File f) { try { FileOutputStream fos = new FileOutputStream(f); ObjectOutputStream oos = new ObjectOutputStream(fos); oos.writeObject(games); oos.writeObject(bookedTickets); oos.writeObject(baggage); oos.close(); fos.close(); } catch (IOException ex) { return false; } return true; } public boolean load(File f) { try { FileInputStream fis = new FileInputStream(f); ObjectInputStream ois = new ObjectInputStream(fis); this.games = (HashMap<Game,GameStatus>)ois.readObject(); this.bookedTickets = (HashSet<Ticket>)ois.readObject(); this.baggage = (HashMap<Ticket,ArrayList<Object>>)ois.readObject(); ois.close(); fis.close(); } catch (IOException e) { return false; } catch (ClassNotFoundException e) { return false; } return true; } . . . } public class JUnitDemo { GameManager manager; @Before public void setUp() { manager = GameManagerSystem.createManagerSystem(Place.ENG); } @Test public void testStore() { Game g = new Game(new Date(), Teams.LIONS, Teams.SHARKS); manager.registerGame(g); File file = new File("file.ser"); assertTrue(airport.store(file)); } }

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  • Java: using generic wildcards with subclassing

    - by gibberish
    Say I have a class Foo, a class A and some subclass B of A. Foo accepts A and its sublclasses as the generic type. A and B both require a Foo instance in their constructor. I want A's Foo to be of type A , and B's Foo to be of type B or a superclass of B. So in effect, So I only want this: Foo<X> bar = new Foo<X>; new B(bar); to be possible if X is either A, B, or a both subclass of A and superclass of B. So far this is what I have: class Foo<? extends A>{ //construct } class A(Foo<A> bar){ //construct } class B(Foo<? super B> bar){ super(bar); //construct } The call to super(...) doesn't work, because <A> is stricter than <? super B>. Is it somehow possible to use the constructor (or avoid code duplication by another means) while enforcing these types? Edit: Foo keeps a collection of elements of the generic parameter type, and these elements and Foo have a bidirectional link. It should therefore not be possible to link an A to a Foo.

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  • Filtering out specific objects from a search query in Alfresco using Java

    - by Snowright
    I have a HashSet containing all groups I've retrieved from my database. I've been asked to filter this result by removing two specific groups. It seems trivial but I can't seem to come up with a solid solution for storing the specific groups I want to filter out. My idea is to just create an array containing references to the two groups I need to filter out. I can then filter out my search query with whatever is in the array. My concern is that in the future they may ask to filter out more groups and maybe an array may not be a good idea. //Creates the array containing groups to filter out String[] hiddenGroups = {"group1","group2"}; //retrieves all groups Set<String>allGroups = new HashSet<String>(); allGroups.addAll(authorityService.getAllAuthorities(AuthorityType.GROUP); List<String>results = new ArrayList<String>(); //filters out specified groups for (String group : allGroups) { boolean isHidden = false; for (String hiddenGroup : hiddenGroups) { if (hiddenGroup.equalsIgnorecase(group)) { isHidden = true; } } if (!isHidden){ results.add(group); } }

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  • Java Collection performance question

    - by Shervin
    I have created a method that takes two Collection<String> as input and copies one to the other. However, I am not sure if I should check if the collections contain the same elements before I start copying, or if I should just copy regardless. This is the method: /** * Copies from one collection to the other. Does not allow empty string. * Removes duplicates. * Clears the too Collection first * @param target * @param dest */ public static void copyStringCollectionAndRemoveDuplicates(Collection<String> target, Collection<String> dest) { if(target == null || dest == null) return; //Is this faster to do? Or should I just comment this block out if(target.containsAll(dest)) return; dest.clear(); Set<String> uniqueSet = new LinkedHashSet<String>(target.size()); for(String f : target) if(!"".equals(f)) uniqueSet.add(f); dest.addAll(uniqueSet); } Maybe it is faster to just remove the if(target.containsAll(dest)) return; Because this method will iterate over the entire collection anyways.

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  • Access files (.wav) in java package

    - by Highmastdon
    I want to access my .wav files which are in a package inside my project. For example I got two packages: package program package sounds From inside the program/something.class I'd like to play the sounds/asound.wav. How is this possible. clip.open(AudioSystem.getAudioInputStream(new File(filename))); clip.start(); //.... something inbetween clip.stop(); Here filename is C:\\projects\\something\\sounds\\, but how is it possible to just give a relative path to the asound.wav in the package?

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  • non blocking client server chat application in java using nio

    - by Amith
    I built a simple chat application using nio channels. I am very much new to networking as well as threads. This application is for communicating with server (Server / Client chat application). My problem is that multiple clients are not supported by the server. How do I solve this problem? What's the bug in my code? public class Clientcore extends Thread { SelectionKey selkey=null; Selector sckt_manager=null; public void coreClient() { System.out.println("please enter the text"); BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in)); SocketChannel sc = null; try { sc = SocketChannel.open(); sc.configureBlocking(false); sc.connect(new InetSocketAddress(8888)); int i=0; while (!sc.finishConnect()) { } for(int ii=0;ii>-22;ii++) { System.out.println("Enter the text"); String HELLO_REQUEST =stdin.readLine().toString(); if(HELLO_REQUEST.equalsIgnoreCase("end")) { break; } System.out.println("Sending a request to HelloServer"); ByteBuffer buffer = ByteBuffer.wrap(HELLO_REQUEST.getBytes()); sc.write(buffer); } } catch (IOException e) { e.printStackTrace(); } finally { if (sc != null) { try { sc.close(); } catch (Exception e) { e.printStackTrace(); } } } } public void run() { try { coreClient(); } catch(Exception ej) { ej.printStackTrace(); }}} public class ServerCore extends Thread { SelectionKey selkey=null; Selector sckt_manager=null; public void run() { try { coreServer(); } catch(Exception ej) { ej.printStackTrace(); } } private void coreServer() { try { ServerSocketChannel ssc = ServerSocketChannel.open(); try { ssc.socket().bind(new InetSocketAddress(8888)); while (true) { sckt_manager=SelectorProvider.provider().openSelector(); ssc.configureBlocking(false); SocketChannel sc = ssc.accept(); register_server(ssc,SelectionKey.OP_ACCEPT); if (sc == null) { } else { System.out.println("Received an incoming connection from " + sc.socket().getRemoteSocketAddress()); printRequest(sc); System.err.println("testing 1"); String HELLO_REPLY = "Sample Display"; ByteBuffer buffer = ByteBuffer.wrap(HELLO_REPLY.getBytes()); System.err.println("testing 2"); sc.write(buffer); System.err.println("testing 3"); sc.close(); }}} catch (IOException e) { e.printStackTrace(); } finally { if (ssc != null) { try { ssc.close(); } catch (IOException e) { e.printStackTrace(); } } } } catch(Exception E) { System.out.println("Ex in servCORE "+E); } } private static void printRequest(SocketChannel sc) throws IOException { ReadableByteChannel rbc = Channels.newChannel(sc.socket().getInputStream()); WritableByteChannel wbc = Channels.newChannel(System.out); ByteBuffer b = ByteBuffer.allocate(1024); // read 1024 bytes while (rbc.read(b) != -1) { b.flip(); while (b.hasRemaining()) { wbc.write(b); System.out.println(); } b.clear(); } } public void register_server(ServerSocketChannel ssc,int selectionkey_ops)throws Exception { ssc.register(sckt_manager,selectionkey_ops); }} public class HelloClient { public void coreClientChat() { Clientcore t=new Clientcore(); new Thread(t).start(); } public static void main(String[] args)throws Exception { HelloClient cl= new HelloClient(); cl.coreClientChat(); }} public class HelloServer { public void coreServerChat() { ServerCore t=new ServerCore(); new Thread(t).start(); } public static void main(String[] args) { HelloServer st= new HelloServer(); st.coreServerChat(); }}

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  • Java: how to use Google's HashBiMap?

    - by HH
    Keys are a file and a word. The file gives all words inside the file. The word gives all files having the word. I am unsure of the domain and co-domain parts. I want K to be of the type <String> and V to be of type <HashSet<FileObject>>. public HashBiMap<K<String>,V<HashSet<FileObject>>> wordToFiles = new HashBiMap<K<String>,V<HashSet<FileObject>>>(); public HashBiMap<K<String>,V<HashSet<FileObject>>> fileToWords = new HashBiMap<K<String>,V<HashSet<FileObject>>>(); Google's HashBiMap.

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  • Selecting based on __key__ (a unique identifier) in google appengine [Java]

    - by Stavros
    I have public class QuantityType { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key key; @Persistent private String type; } I am trying to setup a query to get the right QuantityType by it's key gql = "select * from QuantityType where __key__='aght52oobW1hIHTWVzc2FnZRiyAQw'"; But its not working because BadFilterError: BadFilterError: invalid filter: key filter value must be a Key; received aght52oobW1hIHTWVzc2FnZRiyAQw (a str). I have also tried to use gql = "select * from QuantityType where __key__=='" + KeyFactory.stringToKey(qTypeKey)+"'"; but it's now working.. How can I get a specific object from my datastore by it's key?

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  • Trying to convert a 2D image into 3D objects in Java

    - by Kyle
    Hey, I'm trying to take a simple image, something like a black background with colored blocks representing walls. I'm trying to figure out how to go about starting on something like this. Do I need to parse the image and look at each pixel or is there an easier way to do it? I'm using Java3D but it doesn't seem to have any sort of built in support for that...

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  • how can i acess a variable outside of an if statement in java

    - by themanepalli
    i have defined a variable inside an if statement and I am trying to access it outside of that if statement now. now the error is saying that it cannot find the symbol which is because its being defined as an intance variable, is there a way i can change it so i can access it outside the variable? heres the code if((e.getSource()==userOrder2)&& (orderType==1)) { String buyO= userOrder2.getText(); int buyOrder= Integer.parseInt(buyO); //variable im trying to access } // trying to use buyOrder in a different if statement if(orderType==1 && (stockPrice <= buyOrder)) { orderResult.setText("The Stock" + (stockName2.getText()) + "was bought at" + stockPrice); }

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  • What is the purpose of Finalization in java?

    - by Karthik
    Different websites are giving different opinions. My understanding is this: To clean up or reclaim the memory that an object occupies, the Garbage collector comes into action. (automatically is invoked???) The garbage collector then dereferences the object. Sometimes, there is no way for the garbage collector to access the object. Then finalize is invoked to do a final clean up processing after which the garbage collector can be invoked. is this right?

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  • Java Counting # of occurrences of a word in a string

    - by Doug
    I have a large text file I am reading from and I need to find out how many times some words come up. For example, the word "the". I'm doing this line by line each line is a string. I need to make sure that I only count legit "the"'s the the in other would not count. This means I know I need to use regular expressions in some way. What I was trying so far is this: numSpace += line.split("[^a-z]the[^a-z]").length; I realize the regular expression may not be correct at the moment but I tried without that and just tried to find occurrences of the word the and I get wrong numbers to. I was under the impression this would split the string up into an array and how many times that array was split up was how many times the word is in the string. Any ideas I would be grateful.

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  • Simplest way of creating java next/previous buttons

    - by Holly
    I know that when creating buttons, like next and previous, that the code can be somewhat long to get those buttons to function. My professor gave us this example to create the next button: private void jbtnNext_Click() { JOptionPane.showMessageDialog(null, "Next" ,"Button Pressed", JOptionPane.INFORMATION_MESSAGE); try { if (rset.next()) { fillTextFields(false); }else{ //Display result in a dialog box JOptionPane.showMessageDialog(null, "Not found"); } } catch (SQLException ex) { ex.printStackTrace(); } } Though, I do not really understand how that short and simple if statement is what makes the next button function. I see that the fillTextFields(false) uses a boolean value and that you need to initialize that boolean value in the beginning of the code I believe. I had put private fillTextFields boolean = false; but this does not seem to be right... I'm just hoping someone could explain it better. Thanks :)

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  • Java JMenuItem Accelator Snow Leopard

    - by Jeremy McGee
    about = new JMenuItem("About"); about.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_A((Toolkit.getDefaultToolkit().getMenuShortcutMask())))); JMenu help = new JMenu("Help"); help.add(about); I was wondering why my aaccelerators were not working. I am running this in snow leopard with JavaSe-1.6 VM. They do work if I pull the menu down then try the key sequence. Thanks

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  • Communication via internet in Java

    - by Stuart
    What I mean is like servers on video games. You can run an application and it will set up a server on your computer with an IP and a port. For example, how would you make an application where one host application sets up a thing where it has an IP and a port, and another computer that has access to the internet as well can type in the IP and port and it would be able to communicate with the host? I mean simple communication, like sending a boolean or String. And would there be any security problems that would be needed to fix?

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