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  • Download Large Files using java

    - by angelina
    Dear All, I M building a application in which i want to download large files on handset (mobile),but if size of file is large i m getting exception socket exception-broken pipe . inputStream = new FileInputStream(path); byte[] buffer = new byte[1024]; int bytesRead = 0; do { bytesRead = inputStream.read(buffer, offset, buffer.length); resp.getOutputStream().write(buffer, 0, bytesRead); } while (bytesRead == buffer.length); resp.getOutputStream().flush(); }

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  • Java Flow Control Problem

    - by Kyle_Solo
    I am programming a simple 2d game engine. I've decided how I'd like the engine to function: it will be composed of objects containing "events" that my main game loop will trigger when appropriate. A little more about the structure: Every GameObject has an updateEvent method. objectList is a list of all the objects that will receive update events. Only objects on this list have their updateEvent method called by the game loop. I’m trying to implement this method in the GameObject class (This specification is what I’d like the method to achieve): /** * This method removes a GameObject from objectList. The GameObject * should immediately stop executing code, that is, absolutely no more * code inside update events will be executed for the removed game object. * If necessary, control should transfer to the game loop. * @param go The GameObject to be removed */ public void remove(GameObject go) So if an object tries to remove itself inside of an update event, control should transfer back to the game engine: public void updateEvent() { //object's update event remove(this); System.out.println("Should never reach here!"); } Here’s what I have so far. It works, but the more I read about using exceptions for flow control the less I like it, so I want to see if there are alternatives. Remove Method public void remove(GameObject go) { //add to removedList //flag as removed //throw an exception if removing self from inside an updateEvent } Game Loop for(GameObject go : objectList) { try { if (!go.removed) { go.updateEvent(); } else { //object is scheduled to be removed, do nothing } } catch(ObjectRemovedException e) { //control has been transferred back to the game loop //no need to do anything here } } // now remove the objects that are in removedList from objectList 2 questions: Am I correct in assuming that the only way to implement the stop-right-away part of the remove method as described above is by throwing a custom exception and catching it in the game loop? (I know, using exceptions for flow control is like goto, which is bad. I just can’t think of another way to do what I want!) For the removal from the list itself, it is possible for one object to remove one that is farther down on the list. Currently I’m checking a removed flag before executing any code, and at the end of each pass removing the objects to avoid concurrent modification. Is there a better, preferably instant/non-polling way to do this?

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  • java: assigning object reference IDs for custom serialization

    - by Jason S
    For various reasons I have a custom serialization where I am dumping some fairly simple objects to a data file. There are maybe 5-10 classes, and the object graphs that result are acyclic and pretty simple (each serialized object has 1 or 2 references to another that are serialized). For example: class Foo { final private long id; public Foo(long id, /* other stuff */) { ... } } class Bar { final private long id; final private Foo foo; public Bar(long id, Foo foo, /* other stuff */) { ... } } class Baz { final private long id; final private List<Bar> barList; public Baz(long id, List<Bar> barList, /* other stuff */) { ... } } The id field is just for the serialization, so that when I am serializing to a file, I can write objects by keeping a record of which IDs have been serialized so far, then for each object checking whether its child objects have been serialized and writing the ones that haven't, finally writing the object itself by writing its data fields and the IDs corresponding to its child objects. What's puzzling me is how to assign id's. I thought about it, and it seems like there are three cases for assigning an ID: dynamically-created objects -- id is assigned from a counter that increments reading objects from disk -- id is assigned from the number stored in the disk file singleton objects -- object is created prior to any dynamically-created object, to represent a singleton object that is always present. How can I handle these properly? I feel like I'm reinventing the wheel and there must be a well-established technique for handling all the cases.

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  • Java: Protected classes?

    - by incrediman
    I'd like to be able to have two protected classes in my package. That is, I do not want files outside of my package to see them as visible - they will be for internal use within the package only. How can I do this?

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  • Elements of a Java Object Array are created but without correct names

    - by Greenhouse Gases
    Hi all Im having rather an annoying problem. I have a class called Person and a class called Event which serve to create objects to be used for competitors that compete in a certain event. When I add a competitor thats fine and the GUI list updates accordingly, however when I add an event the element in the array does not take on the value of the instance variable name in the class Event and so the GUI does not show the event name, though it is being added in the array correctly. How can I make it so that the event object in each element of the listOfEvents array (which is an array of event objects) has the name of the event. I should add this is for university though this isnt the part for which we will be assessed, it is somethign i have come across and due to not being able to see the code for the GUI, I've hit the proverbial brick wall. I wont include the whole load of code Ive been writing but hopefully my description and snippets below will suffice. Any advice I would appreciate greatly. No doubt I have overlooked something simple! Many thanks. listOfEvents is declared as: Event[] listOfEvents = new Event[20]; A snippet from the Event class: public class Event { String name; Person[] participants = new Person[10]; // array of competitors for the event public Event(String name) { this.name = name; } } and its use in the addEvent method (p is a global variable): public void addEvent(String eventName) { listOfEvents[p] = new Event(eventName); p++; }

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  • Return an Object in Java

    - by digby12
    I've been struggling to work out how to return an object. I have the following array of objects. ArrayList<Object> favourites; I want to find an object in the array based on it's "description" property. public Item finditem(String description) { for (Object x : favourites) { if(description.equals(x.getDescription())) { return Object x; else { return null; Can someone please show me how I would write this code. Thanks.

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  • java for loop not working

    - by Steve
    I hope this isn't a stupid question but I have looked up every example I can find and it still seems like I have this code right and it still isn't working... I enter one number and it moves on to the next line of code instead of looping. I'm using this to fill an array with user input numbers. I appreciate any help, thanks. for(i=0; i<9; i++); { System.out.println ("Please enter a number:"); Num[i] = keyboard.nextDouble(); Sum += Num[i]; Product *= Num[i]; }

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  • Java application on windows server possibility?

    - by Shawn Mclean
    I'd like to know if it is possible to have this application (neo4j) running on windows server 2008 alongside an asp.net mvc application. Reason for this, I need to access the graph database (neo4j) which provides a RESTful service from my mvc application. How would I go about setting up this architecture?

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  • java hashmap array to double array

    - by Tweety
    Hi, I declared LinkedHashMap<String, float[]> and now I want to convert float[] values into double[][]. I am using following code. LinkedHashMap<String, float[]> fData; double data[][] = null; Iterator<String> iter = fData.keySet().iterator(); int i = 0; while (iter.hasNext()) { faName = iter.next(); tValue = fData.get(faName); //data = new double[fData.size()][tValue.length]; for (int j = 0; j < tValue.length; j++) { data[i][j] = tValue[j]; } i++; } When I try to print data System.out.println(Arrays.deepToString(data)); it doesn't show the data :( I tried to debug my code and i figured out that I have to initialize data outside the while loop but then I don't know the array dimensions :( How to solve it? Thanks

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  • Java splitting string by custom regex match

    - by slikz
    I am completely new to regular expressions so I'm looking for a bit of help here. I am compiling under JDK 1.5 Take this line as an example that I read from standard input: ab:Some string po:bubblegum What I would like to do is split by the two characters and colon. That is, once the line is split and put into a string array, these should be the terms: ab:Some string po:bubblegum I have this regex right now: String[] split = input.split("[..:]"); This splits at the semicolon; what I would like is for it to match two characters and a semicolon, but split at the space before that starts. Is this even possible? Here is the output from the string array: ab Some String po bubblegum I've read about Pattern.compile() as well. Is this something I should be considering?

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  • Java > SimpleDateFormat > Month + 1 Why ?

    - by Natim
    Hello, I am using SimpleDateFormat to display a Calendar like this : public String getDate() { String DATE_FORMAT = "EEEE, dd/MM/yyyy HH:mm:ss"; SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT); System.err.println(date.getTime().getMonth()); return sdf.format(date.getTime()); } The shell returns 6 and the display : mardi, 06/07/2010 12:44:52 It can't be possible ? Why ? Thanks

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  • Collision detection in Java game?

    - by Chetan
    I am developing a game in which I have the problem of collision detection of moving images. The game has a spaceship and number of asteroids (obstacles). I want to detect the collision between them. How can I do this?

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  • ConcurentModificationException in Java HashMap

    - by Bear
    Suppose I have two methods in my classes, writeToMap() and processKey() and both methods are called by multiple threads. writeToMap is a method to write something in hashmap and processKey() is used to do sth based on the keySet of HashMap. Inside processKey, I first copy the originalMap before getting the key set. new HashMap<String, Map<String,String>(originalMap).get("xx").keySet(); But I am still getting ConcurrentModificationException even though I always copy the hashmap. Whats the problem?

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  • java - find out the type of class which implements of other classes

    - by Johnzzz
    i have a kind of specific problem, let's say, that i have public interface A { } //------------------------------ public class B implements A{ static int countx = 0; } //---------------------------------- public class C implements A{ static int county = 0; } //---------------------------------- public class Arc { public A from; public A to; //======================================== and now I have an object a (which is an instance of Arc) and I want to find out whether it is an instance of B or C and get to the atributes countX or countY (stg like a.from.countX) any ideas? :)

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  • Java - Handling Non-Blocking Calls

    - by sarav
    In my application I am using a third-party API. It is a non-blocking method which returns immediately. I have a collection of elements over which I have to invoke this method. Now, my problem is that I have to find a way till all the method execution gets completed and do my next operation. How can I handle this? I cannot modify the third-party API. In short it looks like this for(Object object: objects){ methodA(object); //this is a non-blocking call and returns immediately } // here I want to do my next task only after all the methodA calls completed execution

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  • Need a Java based interruptible timer thread

    - by LambeauLeap
    I have a Main Program which is running a script on the target device(smart phone) and in a while loop waiting for stdout messages. However in this particular case, some of the heartbeat messages on the stdout could be spaced almost 45secs to a 1minute apart. something like: stream = device.runProgram(RESTORE_LOGS, new String[] {}); stream.flush(); String line = stream.readLine(); while (line.compareTo("") != 0) { reporter.commentOnJob(jobId, line); line = stream.readLine(); } So, I want to be a able to start a new interruptible thread after reading line from stdout with a required a sleep window. Upon being able to read a new line, I want to be able to interrupt/stop(having trouble killing the process), handle the newline of stdout text and restart a process. And it the event I am not able to read a line within the timer window(say 45secs) I want to a way to get out of my while loop either. I already tried the thread.run, thread.interrupt approach. But having trouble killing and starting a new thread. Is this the best way out or am I missing something obvious?

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  • Proper usage of Java Weak Reference in case of nested collections

    - by Tong Wang
    I need to define a weak reference Map, whose value is a Set. I use Google collections' MapMaker, like this: Map<Class<? extends Object>, Set<Foo>> map = new MapMaker().weakKeys().weakValues().makeMap(); So, for Set<Foo>, can I use a normal HashSet? Or, do I have to create a weak HashSet, like this: Collections.newSetFromMap(new WeakHashMap<Foo, Boolean>()); And why? Another question, the key of my map is Class objects, when will a Class object become weakly reachable? In other words, what is the lifetime of a Class object? Thanks.

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  • Java BCEL creating method with sipush?

    - by user1446924
    Well, I'm trying to recreate this method : public int getBaseX() { return this.x + 10000; } and it returns these instructions 0 aload_0 1 getfield #18 <TestClass.x> 4 sipush 10000 7 iadd 8 ireturn Now I'm having trouble withe the sipush, iadd. ClassGen injCG = cg; ConstantPoolGen cpg = injCG.getConstantPool(); InstructionList il = new InstructionList(); MethodGen mg = new MethodGen(Constants.ACC_PUBLIC, f.getType(), Type.NO_ARGS, null, name, injCG.getClassName(), il, cpg); InstructionFactory instrF = new InstructionFactory(injCG, cpg); if (!f.isStatic()) il.append(new org.apache.bcel.generic.ALOAD(0)); il.append(instrF.createFieldAccess(cg.getClassName(), f.getName(), f.getType(), (f.isStatic() ? Constants.GETSTATIC : Constants.GETFIELD))); il.append(InstructionFactory.createPop(1000)); il.append(InstructionFactory.createReturn(f.getType())); //il.append(InstructionFactory.createReturn(f.getType()), InstructionFactory.createDup(1000)); mg.setMaxLocals(); mg.setMaxStack(); injCG.addMethod(mg.getMethod()); that's what I have tried, but failed.

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