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  • Does HashMap provide a one to one correspondence?

    - by Roman
    I found the following statement: Map is an object that stores key/volume pairs. Given a key, you can find its value. Keys must be unique, but values may be duplicated. For example I have just one key/value pair (3,4). And now I put a new pair (3,5). It will remove the old pair. Right? But if I put (2,4) instead of (3,4) I will add a new pair of key/value to the HashMap. Right?

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  • Is nested synchronized block necessary?

    - by Dan
    I am writing a multithreaded program and I have a method that has a nested synchronized blocks and I was wondering if I need the inner sync or if just the outer sync is good enough. public class Tester { private BlockingQueue<Ticket> q = new LinkedBlockingQueue<>(); private ArrayList<Long> list = new ArrayList<>(); public void acceptTicket(Ticket p) { try { synchronized (q) { q.put(p); synchronized (list) { if (list.size() < 5) { list.add(p.getSize()); } else { list.remove(0); list.add(p.getSize()); } } } } catch (InterruptedException ex) { Logger.getLogger(Consumer.class.getName()).log(Level.SEVERE, null, ex); } } } EDIT: This isn't a complete class as I am still working on it. But essentially I am trying to emulate a ticket machine. The ticket machine maintains a list of tickets in the BlockingQueue q. Whenever a client adds a ticket to the machine, the machine also keeps track of the price of the last 5 tickets (ArrayList list)

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  • Returning the element number of the longest string in an array

    - by JohnRoberts
    I'm trying to get the longestS method to take the user-inputted array of strings, then return the element number of the longest string in that array. I got it to the point where I was able to return the number of chars in the longest string, but I don't believe that will work for what I need. My problem is that I keep getting incompatible type errors when trying to figure this out. I don't understand the whole data type thing with strings yet. It's confusing me how I go about return a number of the array yet the array is of strings. The main method is fine, I got stuck on the ???? part. { public static void main(String [] args) { Scanner inp = new Scanner( System.in ); String [] responseArr= new String[4]; for (int i=0; i<4; i++) { System.out.println("Enter string "+(i+1)); responseArr[i] = inp.nextLine(); } int highest=longestS(responseArr); } public static int longestS(String[] values) { int largest=0 for( int i = 1; i < values.length; i++ ) { if ( ????? ) } return largest; } }

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  • Design Pattern for Server Emulator

    - by adisembiring
    I wanna build server socket emulator, but I want implement some design pattern there. I will described my case study that I have simplified like these: My Server Socket will always listen client socket. While some request message come from the client socket, the server emulator will response the client through the socket. the response is response code. '00' will describe request message processed successfully, and another response code expect '00' will describe there are some error while processing the message request. IN the server there are some UI, this UI contain check response parameter such as. response code timeout interval While the server want to response the client message, the response code taken from input parameter response form UI check the timeout interval, it will create sleep thread and the interval taken from timeout interval input from UI. I have implement the function, but I create it in one class. I feel it so sucks. Can you suggest me what class / interface that I must create to refactor my code.

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  • how do you print a bag datatype?

    - by shiva
    Bag<String> wordFrequencies = getWordFrequencies(text); how do i see what this wordfrequencies bag contains.. i ve used org.apache.commons.collections15.Bag org.apache.commons.collections15.bag.HashBag packages

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  • Updating position of JSlider Swing

    - by GLRockwell
    My apologies for posting tons of questions as of late. I'm trying to get a JSlider to update its position based on a constantly updating variable. The setValue(n) method doesn't seem to work. Is there any alternative? We're using this as a time marker for a music player.

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  • Object can not be resolved.

    - by Gabriel A. Zorrilla
    I have this code: public class Window extends JFrame { public Window(){ ... JButton button = new JButton("OK"); getContentPane().add(button); ButtonHandler handler = new ButtonHandler(); button.addActionListener(handler); ... } private class ButtonHandler implements ActionListener { public void actionPerformed(ActionEvent event){ if (event.getSource() == button){ // <--- "button can not be resolved" System.out.println("Hello"); } } } I'm getting that error in Eclipse. I just made a (simplified) example found in a book, dont know what can be wrong. Knowledge eye required! :)

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  • Using a Session Scoped Bean

    - by jboyd
    The following code is returning null: private MyAppUser getMyAppUser(HttpSession session) { MyAppUser myAppUser = (MyAppUser) session.getAttribute("myAppUserManager"); return myAppUser; } Despite the fact that I have the following in my context: <bean id="myAppUserManager" class="com.myapp.profile.MyAppUser" scope="session"/> This doesn't make any sense to me, the "myAppUser" bean is a bean that absolutely can never be null, and I need to be able to reference it from controllers, I don't need it in services or repositories, just controllers, but it doesn't seem to be getting stored in the session, the use case is extremely simple, but I haven't been able to get to the bottom of what's wrong, or come up with a good workaround

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  • Invalid ADTS sampling_frequency_index and channel_configuration why?

    - by Moto
    Hello all, I hope someone can direct me on the right path before I put a lot of time and effort on this. I'm currently trying to parse an AAC+ frame to get information such as number of channels and sample frequency. So it seems that we can simply get this information from the ADTS header but most of the time this information is inaccurate. So the question is: -Why is this data inaccurate? What is the meaning of the ADTS header channel and sample freq? Should I rely on it? -Should I parse further down the frame to get this information? FYI, the AAC+ raw data is coming from streaming servers... Thanks for the help! -Moto

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  • Swing verify code on event dispatch thread at runtime

    - by Jeff Storey
    Are there any libraries that instrument code to verify that methods called on swing components are called on the event dispatch thread? It probably wouldn't be too difficult to write some basic code for doing this, but I'm sure there are edge cases and whatnot that other people have handled. I'm looking for this at runtime though, not for unit tests. thanks, Jeff

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  • creational pattern for instances depending on multiple subclass instances

    - by markusw
    I have a problem, for that I was not able to identify a suitable design pattern. I want to create instances depending on a given type that has been passed to a factory method. What I am doing until now is the following: T create(SuperType x) { if (x instanceof SubType1) { // do some stuff and return a new SubType extends T } else if (x instanceof SubType2) { // do some stuff and return a new SubType extends T } else if ... } else { throw new UnSupportedOperationException("nothing defined for " + x); } } It seems not to be best pratice for me. Has anybody an idea how to solve this in a better way?

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  • Unable to set mouse cursor JLayeredPane

    - by Ones3k2
    I'm running into a problem that I can't seem to figure out nor find the answer anywhere on the web. I've got a JLayeredPane and when it only has one child Panel I am able to correctly set the cursor using setCursor(). The cursor shows up and everything is fine. But when I add an additional JPanel into the JLayeredPane the cursor no longer shows up for example this works: m_layeredPane = new JLayeredPane(); m_layeredPane.setLayout(new WBLayoutManager()); m_layeredPane.add(m_mediaPanel, new Integer(0)); // m_layeredPane.add(m_whiteboardPanel, new Integer(1)); m_layeredPane.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR)); // WORKS but this doesn't: m_layeredPane = new JLayeredPane(); m_layeredPane.setLayout(new WBLayoutManager()); m_layeredPane.add(m_mediaPanel, new Integer(0)); m_layeredPane.add(m_whiteboardPanel, new Integer(1)); m_layeredPane.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR)); // FAILS Anyone know how i can get custom cursors working within a JLayeredPane

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  • How to initiate chatting between two clients and two clients only, using applets and servlets?

    - by mithun1538
    Hello everyone, I first need to apologize for my earlier questions. (You can check my profile for them)They seemed to ask more questions than give answers. Hence, I am laying down the actual question that started all them absurd questions. I am trying to design a chat applet. Till now, I have coded the applet, servlet and communication between the applet and the servlet. The code in the servlet side is such that I was able to establish chatting between clients using the applets, but the code was more like a broadcast all feature, i.e. all clients would be chatting with each other. That was my first objective when I started designing the chat applet. The second step is chatting between only two specific users, much like any other chat application we have. So this was my idea for it: I create an instance of the servlet that has the 'broadcast-all' code. I then pass the address of this instance to the respective clients. 2 client applets use the address to then chat. Technically the code is 'broadcast-all', but since only 2 clients are connected to it, it gives the chatting between two clients feature. Thus, groups of 2 clients have different instances of the same servlet, and each instance handles chatting between two clients at a max. However, as predicted, the idea didn't materialize! I tried to create an instance of the servlet but the only solution for that was using sessions on the servlet side, and I don't know how to use this session for later communications. I then tried to modify my broadcast-all code. In that code, I was using classes that implemented Observer and Observable interfaces. So the next idea that I got was: Create a new object of the Observable class(say class_1). This object be common to 2 clients. 2 clients that wish to chat will use same object of the class_1. 2 other clients will use a different object of class_1. But the problem here lies with the class that implements the Observer interface(say class_2). Since this has observers monitoring the same type of class, namely class_1, how do I establish an observer monitoring one object of class_1 and another observer monitoring another object of the same class class_1 (Because notifyObservers() would notify all the observers and I can't assign a particular observer to a particular object)? I first decided to ask individual problems, like how to create instances of servlets, using objects of observable and observer and so on in stackoverflow... but I got confused even more. Can anyone give me an idea how to establish chatting between two clients only?(I am using Http and not sockets or RMI). Regards, Mithun. P.S. Thanks to all who replied to my previous (absurd) queries. I should have stated the purpose earlier so that you guys could help me better.

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  • Webwork actions, the lifecycle of variables declared in the action class.

    - by Sam
    Hi all, I'm using the webwork framework (JIRA plugin development) and was wondering about the lifecycle of the variables in the action class. I have a few private variables in the action class that are set when during the doDefault() method. These are used in the input view to set up jqGrid columns and then when the user has entered some data they click submit which puts the grid data into a hidden input. The next thing that happens is the doValidation() method is called before the doExecute(), which displays the input view if there are any errors. The problem is that the variables set up in the doDefault() method are now null. Can anyone explain to me how the lifecycle of variables works in the webwork actions? Cheers

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  • Can I fix the width of JRadioButton?

    - by Roman
    I have sever JPanels which have to be ordered vertically. For that I want to fix the width of the JPanels. Because if they are too short in comparison with the windows width, they will go horizontally (one after another) and I do not want it. At the moment the width of the JPanel is not constant because the width of the JRadioButton (included into JPabel) is not constant. How can I make the width of the JRadioButton constant? At the moment it is not constant because of the label (which can be different).

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  • Anybody using Qi4J

    - by Jon
    I was reading an InfoQ article on Composite Oriented Programming earlier on: http://www.infoq.com/articles/Composite-Programming-Qi4j I was interested in finding out whether anybody is currently using (or has used) the Qi4j framework at all? How does it compares to using a traditional dependency injection framework such as Spring for wiring classes together. Is the resulting object graph (based on mixins rather than classes) easier to deal with from a maintenance point of view?

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  • How could I get an .ear's filesize at runtime?

    - by adam
    I started out attempting to do this with the Length ant task, but realized that that would be done before the ear is packaged. Packaging the ear, then checking the file size, and then placing it in the ear would effect the size of the ear. Is there a way to get the ear's size programmatically at run-time? Or perhaps an MBean that would have that information?

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  • JUnit: checking if a void method gets called

    - by nkr1pt
    I have a very simple filewatcher class which checks every 2 seconds if a file has changed and if so, the onChange method (void) is called. Is there an easy way to check ik the onChange method is getting called in a unit test? code: public class PropertyFileWatcher extends TimerTask { private long timeStamp; private File file; public PropertyFileWatcher(File file) { this.file = file; this.timeStamp = file.lastModified(); } public final void run() { long timeStamp = file.lastModified(); if (this.timeStamp != timeStamp) { this.timeStamp = timeStamp; onChange(file); } } protected void onChange(File file) { System.out.println("Property file has changed"); } } @Test public void testPropertyFileWatcher() throws Exception { File file = new File("testfile"); file.createNewFile(); PropertyFileWatcher propertyFileWatcher = new PropertyFileWatcher(file); Timer timer = new Timer(); timer.schedule(propertyFileWatcher, 2000); FileWriter fw = new FileWriter(file); fw.write("blah"); fw.close(); Thread.sleep(8000); // check if propertyFileWatcher.onChange was called file.delete(); }

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  • Force close problem

    - by neetha-ann
    While i'm clicking a button in my menu list (for example select all)my application is getting force closed.Why is it so???in eclipse emulator it is working fine,but in phone(i'm using LG620)it's getting force closed,as i've no cable with me,i can't debug it.

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  • Updatable false behvior incosistent

    - by jpanewbie
    I need LastUpdatedDttm to be updated by SYSDATE whenever record is updated. But below annoataions do nt work as desired. SYSDATE is inserted only once and not updated for subsequent updations. Also, lastUpdDTTM is not part of sql generated by hibernate. @Generated(GenerationTime.ALWAYS) @Column(name="LAST_UPDATED_DTTM",insertable=false,updatable=true, columnDefinition ="timestamp default SYSDATE") private Date lastUpdDTTM; @Generated(GenerationTime.ALWAYS) @Column(name="CREATED_DTTM", insertable=false, updatable=false) private Date createdDTTM;

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