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  • how to remove ConcurrentModificationException

    - by maverick
    what is this exception and how to remove this in my problem i am creating an arraylist of objects, and after checking some condition,i want to remove some objects. but the program is giving this exception ConcurrentModificationException. how to remove this thanks in advance

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  • JBoss 6 unpacks jars from WEB-INF/lib of war

    - by Maxym
    when I start JBoss 6 I see that it unpacks all jar files from WEB-INF/lib in tmp/vfs/automountXXX folder. E.g. jackrabbit-server.war contains library asm-3.1.jar, then in tmp folder I see the following folders with files: asm-3.1.jar-83dc35ead0d41d41/asm-3.1.jar asm-3.1.jar-2a48f1c13ec7f25d/contents/"unpacked asm-3.1.jar" it does not take files from my.ear/lib only WEB-INF/lib... Why is it so? And is here any way to prevent it doing so? It just slows down application server starting (and stopping), what is not that comfortable at development... If it is somehow related to JavaEE 6 specification and ejb-jars, which can be located now in WEB-INF/lib, so I don't have such libraries in my war files... UPDATE: actually when I repack jackrabbit-server.war to jackrabbit-server.ear which contains jackrabbit-server.war and moved all its libraries to jackrabbit-server.ear/lib then I still see two folders in tmp: asm-3.1.jar-215a36131ebb088e/asm-3.1.jar asm-3.1.jar-14695f157664f00/contents/ but in this case last folder is empty. So it still creates two folders, but does not unpack my library. Also I use exploded deployment so the question is only about jar files, not unpacking ear/war.

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  • Caching instances in a jee web app

    - by SibzTer
    Hi, Consider the scenario of a typical webapp with JSFs on the front and ejb3, with Hibernate as JPA provider, talking to backend database such as mysql, etc. The main user actions are login and mostly CRUD operations (minus any D(elete) operations). And the App Server is GlassFish of course. Given this scenario, how and where all would one go about providing caching to improve performance? From what I have googled, I have seen that hibernate provides some sort of caching through different cache providers. Is there any sort of caching that can be provided for the jsf pages? How about session beans or entity beans on the ejb side of things? Also, I just read about memcached and was wondering if this was something to consider?

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  • if-else structure

    - by Halo
    I have these long statements that I will refer to as x,y etc. here. My conditional statements' structure goes like this: if(x || y || z || q){ if(x) do someth else if (y) do something if(z) do something else if(q) do something } else do smthing Is there a better, shorter way to write this thing? Thanks

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  • Concurrent Programming:Should I write a sequential program first, then add thread safety?

    - by evthim
    I'm working on a project where we have to create a number of threads(actual number will be inputted in by testers (TA's)). I'm having trouble not only with the programming but also with the design, I can't wrap my head around all of the threads that will be invoked and where I might cause errors. The project is due soon so I don't want to waste time on this if it'll actually set me back, but I was wondering if I should write the program like only one thread will be running and everything should be sequential and then later go back and try to add the thread safety parts of the code? Would that take twice the original amount of time? Project Description: Note:I'm going to be as vague as possible so I don't violate any honor codes, sorry :( your program should accept n number of objectA threads, m number of objectB threads, and r number of objectC objectB threads interact with code in objectA. objectA threads interact with code in objectB and objectC objectB and objectC don't directly interact, but do so indirectly through objectA -ex: objectB needs something from objectA. objectA gets the result for that something by calling objectC my confusion stems mostly from the fact that all of this interactions will be done by m+n threads and there are various restrictions throughout the descriptions, like objectB can request something from objectA, and objectA has to wait for objectC to finish that something before returning it to objectB. Also each objectA thread can only work on one instruction from objectB at a time, etc. etc. I just want to know if I write the code so that there is only 1 objectA, 1 objectB and 1 object C, can I go back and easily modify it so that those 1's can be changed to m, n and r? Sorry again, if my description is a little bit confusing.

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  • How to get value of h:inputText when binded in JSF

    - by Tr?n Minh Phuong
    How can i get 2 h:inputTextValue from this? <h:dataTable cellspacing="0" value="#{managerManagedBean.lstMatch}" var="m" binding="#{managerManagedBean.datatableMatch}"> <!-- cellspacing='0' is important, must stay --> <h:column> <f:facet name="header">Team One</f:facet> <h:outputText value="#{m.teamOneName}"></h:outputText> </h:column> <h:column> <f:facet name="header">Match Score</f:facet> <h:inputText value="#{m.teamOneResult}" style="width: 20px; text-align: center" binding="#{input}"></h:inputText> - <h:inputText value="#{m.teamTwoResult}" style="width: 20px; text-align: center"></h:inputText> </h:column> <h:column> <f:facet name="header">Half Time</f:facet> <h:outputText value="#{m.haveHalfTime}"></h:outputText> </h:column> <h:column> <f:facet name="header">Team Two</f:facet> <h:outputText value="#{m.teamTwoName}"></h:outputText> </h:column> <h:column> <f:facet name="header">Match Date</f:facet> <h:outputText value="#{m.matchDate}"></h:outputText> </h:column> <h:column> <f:facet name="header">Control</f:facet> <h:commandButton action="#{managerManagedBean.update(m, input.value)}" value="Update Match"> </h:commandButton> </h:column> </h:dataTable>

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  • Components don't show in custom JPanel/JComponent

    - by Bart van Heukelom
    I've created a custom swing component. I can see it (the grid from the paint method is drawn), but the buttons that are added (verified by println) aren't shown. What am I doing wrong? Background information: I'm trying to build a tree of visible objects like the Flash/AS3 display list. public class MapPanel extends JComponent { // or extends JPanel, same effect private static final long serialVersionUID = 4844990579260312742L; public MapPanel(ShapeMap map) { setBackground(Color.LIGHT_GRAY); setPreferredSize(new Dimension(1000,1000)); setLayout(null); for (Layer l : map.getLayers()) { // LayerView layerView = new LayerView(l); // add(layerView); System.out.println(l); JButton test = new JButton(l.getName()); add(test); validate(); } } @Override protected void paintComponent(Graphics g) { // necessary? super.paintComponent(g); // background g.setColor(getBackground()); g.fillRect(0, 0, getWidth(), getHeight()); // grid g.setColor(Color.GRAY); for (double x = 0; x < getWidth(); x += 10) { g.drawLine((int)x, 0, (int)x, getHeight()); } for (double y = 0; y < getHeight(); y += 10) { g.drawLine(0, (int)y, getWidth(), (int)y); } } }

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  • Where are the really high quality and complex Swing components?

    - by jouhni
    Looking at Swing, I have the feeling that it comes with many useful and reasonable atomic components in its core. And when I look at the Web there are hundrets of quickly plugged together components (among them many date/time pickers, pimped lists and tables), which have in common that I could easily write them on my own, if I needed them. When I build big software and come to the point where I need a domain-specific component which is really big, I mostly come to the point where I have to write it on my own, which, due to the point that they are not just plugged together lists and tables, isn't done qickly. So, the question is, why are there no Swing component galleries which contain more than just customized date/time pickers or lists with added tree support. Where are the components which really raise the level of abstraction, or are in best case domain-specific?

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  • Drawing graphics on top of a JButton

    - by trinth
    I have a situation wherein I have a bunch of JButtons on a GridLayout. I need each of the JButtons to have: a background image (but retain the ability to keep the default button look if needed) custom graphics drawn on top by other classes I have no trouble with the background image, since I am using setIcon() but I am having problems drawing things on top of the background. At one point I was able to draw on top of the button, but after the button was clicked, the drawings disappeared. How can make the button keep this drawing state? Basically, I need a way for my JButtons to have public methods that would allow another class to draw anything on it such as: public void drawSomething() { Graphics g = this.getGraphics(); g.drawOval(3,2,2,2); repaint(); } or public Graphics getGraphics() { return this.getGraphics(); } then another class could do this: button.getGraphics().drawSomething(); The latter is more what I am looking for but the first is equally useful. Is there any way to go about this? Also, overriding the parent class method paintComponent() doesn't help since I need each button to have different graphics.

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  • Threadsafe way of exposing keySet()

    - by Jake
    This must be a fairly common occurrence where I have a map and wish to thread-safely expose its key set: public MyClass { Map<String,String> map = // ... public final Set<String> keys() { // returns key set } } Now, if my "map" is not thread-safe, this is not safe: public final Set<String> keys() { return map.keySet(); } And neither is: public final Set<String> keys() { return Collections.unmodifiableSet(map.keySet()); } So I need to create a copy, such as: public final Set<String> keys() { return new HashSet(map.keySet()); } However, this doesn't seem safe either because that constructor traverses the elements of the parameter and add()s them. So while this copying is going on, a ConcurrentModificationException can happen. So then: public final Set<String> keys() { synchronized(map) { return new HashSet(map.keySet()); } } seems like the solution. Does this look right?

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  • How to know file type without extension

    - by Ayusman
    While trying to come-up with a servlet based application to read files and manipulate them (image type conversion) here is a question that came up to me: Is it possible to inspect a file content and know the filetype? Is there a standard that specifies that each file MUST provide some type of marker in their content so that the application will not have to rely on the file extension constraints? Consider an application scenario: I am creating an application that will be able to convert different file formats to a set of output formats. Say user uploads an PDF, my application can suggest that the possible conversion formats are microsoft word or TIFF or JPEG etc. As my application will gradually support different file formats (over a period of time), I want my application to inspect the input file instead of having the user to specify the format. And suggest to user the possible formats of output. I understand this is an open ended, broad question. Please let me know if it needs to be modified. Thanks, Ayusman

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  • Inserting an element into a sorted list

    - by Russell Cargill
    Ok I'm using getSharedPreferences to store my high score but before I fill it up I wanted to sort the scores into ascending order via and array, but if it finds a Score less than it in the first pos then it wont check the rest for the smallest? //function to add score to array and sort it public void addscoretoarray(int mScore){ for(int pos = 0; pos< score.length; pos++){ if(score[pos] > mScore){ //do nothing }else { //Add the score into that position score[pos] = mScore; break; } } sortArray(score); } should I call sortArray() before and after the loop to fix this problem or is there a better method to achive the same results? I should also mention that the sortArray(score) funtion is just calling Arrays.sort(score) where score is an array of mScore

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  • Hibernate/JPA - annotating bean methods vs fields

    - by Benju
    I have a simple question about usage of Hibernate. I keep seeing people using JPA annotations in one of two ways by annotating the fields of a class and also by annotating the get method on the corresponding beans. My question is as follows: Is there a difference between annotating fields and bean methods with JPA annoations such as @Id. example: @Entity public class User { **@ID** private int id; public int getId(){ return this.id; } public void setId(int id){ this.id=id; } } -----------OR----------- @Entity public class User { private int id; **@ID** public int getId(){ return this.id; } public void setId(int id){ this.id=id; } }

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  • Encrypt string with public key only

    - by vlahovic
    i'm currently working on a android project where i need to encrypt a string using 128 bit AES, padding PKCS7 and CBC. I don't want to use any salt for this. I've tried loads of different variations including PBEKey but i can't come up with working code. This is what i currently have: String plainText = "24124124123"; String pwd = "BobsPublicPassword"; byte[] key = pwd.getBytes(); key = cutArray(key, 16); byte[] input = plainText.getBytes(); byte[] output = null; SecretKeySpec keySpec = null; keySpec = new SecretKeySpec(key, "AES"); Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding"); cipher.init(Cipher.ENCRYPT_MODE, keySpec); output = cipher.doFinal(input); private static byte[] cutArray(byte[] arr, int length){ byte[] resultArr = new byte[length]; for(int i = 0; i < length; i++ ){ resultArr[i] = arr[i]; } return resultArr; } Any help appreciated //Vlahovic

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  • Deploying my flex application

    - by Vatsala
    Hi, I am doing some trial testing awith Amazon ec2 boxes, deploying flex apps running on top of restlet powered webservices. I have this problem - Everytime i deploy the app to the cloud, I'm having to hardcode the IP address of the server into the ActionScript/MXML files (http://72.93.48.39:8080/xxx/abc/) and for certain reasons, i am forced to choose a different IP everytime. and i think its really not the right way to deploy the application. I would like to know what other people do in such scenarios? On thinking about it, i thought i could make it pickup values from the HTMLVars of the HTML wrapper. but that again has to be edited everytime again and again. will it be possible to be able to supply these values : server's ip address, server's port number(in case its not 8080 on some machine) at build time? if so can anyone give me a barbones sample build.xml just as an example?

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  • unable to set fields of a collection-property elements after changing their order (elements becoming

    - by Jaroslav Záruba
    Hello I want to change order of objects in a collection, and then to access+modify fields of those items. Unfortunately the items somehow become 'deleted'. This is what I do... if(someCondition) { MainEvent mainEvent = pm.getObjectById(MainEvent.class, mainEventKey); /* * events in the original order * MainEvent.subEvents field is not in default fetch group, * therefore I also tried to add the named group into the * persistenceManeger fetch plan, no difference * (mainEvent is not instance of the Event sub/class BTW) */ List<Event> subEvents = mainEvent.getSubEvents(); // re-arrange the events according to keysOrdered { Map<Key, Event> eventMap = new HashMap<Key, Event>(); for(Event event : subEvents) eventMap.put(event.getKey(), event); List<Event> eventsOrdered = new LinkedList<Event>(); for(Key eventKey : keysOrdered) eventsOrdered.add(eventMap.put(eventKey, eventMap.get(eventKey))); // } // put the re-arranged items back into the collection property { subEvents.clear(); subEvents.addAll(eventsOrdered); // } pm.makePersistent(mainEvent); eventsOrdered = subEvents; } else eventsOrdered = getEventsUsingAlternateApproach(); /* * so by now the mainEvent variable does not exist; * could it be this lead the persistence manager to mark * my events as abandoned/obsolete/invalid/deleted...? */ for(Event event : eventsOrdered) event.setDate(new Date()); // -> "Cannot write fields to a deleted object" What am I doing wrong please?

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  • How to copy generically superclass instances to subclass instances?

    - by gerry
    Hi @all, I have a class hierarchy / inheritance like this: public class A { private String name; // with getters & setters public void doAWithName(){ ... } } public class B extends A { public void doBWithName(){ // a differnt implementation to what I do in class A } } public class C extends B { public void doCWithName(){ // a differnt implementation to what I do in class A and B } } So at one time there is a instance of class A with the initialized field "name". Later I want this instance of A get wrapped into instance of B or C. So the superclasses should be get wrapped with a subclass! How can I make this most efficent with respect to DRY? I've thought about a constructor that does some copying with the getters/setters. But in this case I have to repeat myself - and this doesn't respect anymore to my initial requirement of DRY! So, how can I warp A to B by just initializing B's new fields (with default values) and delegating the rest to a method in A (which knows more than B about which fields of A should be accessed...). In the same way: If A should be wrapped into C only a method in c should init C's 'new' fields, delegate to B's wrap method (which therefore inits B's 'new' fields in C) and at last B delegates to A which copies it's fields to the fields of C). So in the end I have a new instance of C which has the values of A wrapped (and some default init values to the fields which the inheritance hierarchy has added).

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  • Make process run on non EDT (event dispatch thread) thread from EDT

    - by Aly
    I have a method running on the EDT and within that I want to make it execute something on a new (non EDT) thread. My current code is follows: @Override public void actionPerformed(ActionEvent arg0) { //gathering parameters from GUI //below code I want to run in new Thread and then kill this thread/(close the JFrame) new GameInitializer(userName, player, Constants.BLIND_STRUCTURE_FILES.get(blindStructure), handState); }

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  • list or container O(1)-ish insertion/deletion performance, with array semantics

    - by Chris Kaminski
    I'm looking for a collection that offers list semantics, but also allows array semantics. Say I have a list with the following items: apple orange carrot pear then my container array would: container[0] == apple container[1] == orangle container[2] == carrot Then say I delete the orange element: container[0] == apple container[1] == carrot I don't particularly care if sort order is maintained, I'd just like the array values to function as accelerators to the list items, and I want to collapse gaps in the array without having to do an explicit resizing.

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  • Why should I override hashCode() when I override equals() method?

    - by Bragaadeesh
    Ok, I have heard from many places and sources that whenever I override the equals() method, I need to override the hashCode() method as well. But consider the following piece of code package test; public class MyCustomObject { int intVal1; int intVal2; public MyCustomObject(int val1, int val2){ intVal1 = val1; intVal2 = val2; } public boolean equals(Object obj){ return (((MyCustomObject)obj).intVal1 == this.intVal1) && (((MyCustomObject)obj).intVal2 == this.intVal2); } public static void main(String a[]){ MyCustomObject m1 = new MyCustomObject(3,5); MyCustomObject m2 = new MyCustomObject(3,5); MyCustomObject m3 = new MyCustomObject(4,5); System.out.println(m1.equals(m2)); System.out.println(m1.equals(m3)); } } Here the output is true, false exactly the way I want it to be and I dont care of overriding the hashCode() method at all. This means that hashCode() overriding is an option rather being a mandatory one as everyone says. I want a second confirmation.

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