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  • NullPointerException when trying to add an object to a PriorityQueue

    - by meagan
    i keep getting a null pointer exception when trying to add an object to a priority queue i initialize the queue: private PriorityQueue<NodeObject> nodes; and here i try to add to it: NodeObject childNode = new NodeObject(child, 1); nodes.add(childNode); why doesn't this work? i know my NodeObject is not null because i create it right before i add it.

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  • How can I find a package?

    - by Roman
    In my code I have the following statement import com.apple.dnssd.*; and compiler (javac) complains about this line. It writes that the package does not exist. But I think that it could be that "javac" search the package in a wrong place (directory). In this respect I have two questions: How can I know where javac search for the packages? I think that it is very likely that I have the above mentioned package but I do not know where it is located. What are the typical place to look for the packages?

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  • OO vs Simplicity when it comes to user interaction

    - by Oetzi
    Firstly, sorry if this question is rather vague but it's something I'd really like an answer to. As a project over summer while I have some downtime from Uni I am going to build a monopoly game. This question is more about the general idea of the problem however, rather than the specific task I'm trying to carry out. I decided to build this with a bottom up approach, creating just movement around a forty space board and then moving on to interaction with spaces. I realised that I was quite unsure of the best way of proceeding with this and I am torn between two design ideas: Giving every space its own object, all sub-classes of a Space object so the interaction can be defined by the space object itself. I could do this by implementing different land() methods for each type of space. Only giving the Properties and Utilities (as each property has unique features) objects and creating methods for dealing with the buying/renting etc in the main class of the program (or Board as I'm calling it). Spaces like go and super tax could be implemented by a small set of conditionals checking to see if player is on a special space. Option 1 is obviously the OO (and I feel the correct) way of doing things but I'd like to only have to handle user interaction from the programs main class. In other words, I don't want the space objects to be interacting with the player. Why? Errr. A lot of the coding I've done thus far has had this simplicity but I'm not sure if this is a pipe dream or not for larger projects. Should I really be handling user interaction in an entirely separate class? As you can see I am quite confused about this situation. Is there some way round this? And, does anyone have any advice on practical OO design that could help in general?

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  • What web UI framework is most suitable for building dynamic pages / forms?

    - by waxwing
    Hello, We are at a stage where we are considering different Web UI frameworks (most likely component based ones such as GWT, JSF, Wicket, Vaadin, etc). One of the main use cases / constraints is that it must support generating dynamic pages. I.e., the page/form layout and components is stored in a database and is changeable at runtime, and from this pages are generated. We are also going to write static layouts, but that is not the main focus of this question. I thought maybe the user community here can share experiences of different frameworks in this context. Are there differences in ease of implementation and what is suitable?

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  • How do I implement a listener pattern over RMI using Spring?

    - by predhme
    So here is a generalized version of our application desgin: @Controller public class MyController { @Autowired private MyServiceInterface myServiceInterface; @RequestMapping("/myURL") public @ResponseBody String doSomething() { MyListenerInterface listener = new MyListenerInterfaceImpl(); myServiceInterface.doThenCallListener(listener); // do post stuff } } public interface MyListenerInterface { public void callA(); public void callB(); } public class MyListenerInterfaceImpl implements MyListenerInterface { // ... omitted for clarity } public interface MyServiceInterface { public void doThenCallListener(MyListenerInterface listener); } public class MyServiceImpl { public void doThenCallListener(MyListenerInterface listener) { // do stuff listener.callA(); } } Basically I have a controller that is being called via AJAX in which I am looking to return a response as a string. However, I need to make a call to the backend (MyServiceInterface). That guy is exposed through RMI by using Spring (man that was easy). But the service method as described requires a listener to be registered for invokation completion purposes. So what I assume I need to achieve is transparently to the backend make it so that when the listener methods are called, really the call is going over RMI. I would have thought Spring would have a simple way to wrap a POJO (not a service singleton) with RMI calls. I looked through their documentation but they had nothing besides exposing services via RMI. Could someone point me in the right direction?

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  • Accessing FacesContext from Web Service

    - by scriptmonster
    I'm developing a Web Service which will be called by clients which are written by me. In the web service I need to use application-wide objects which eases the load of application on the system. I have implemented my application-wide objects as shown in this question. I can use my object in a jsf page with no problem as follows. MyObject mo = (MyObject) FacesContext.getCurrentInstance().getExternalContext().getApplicationMap().get("MyObjectsName"); But when it comes to use it in a Web Service Request FacesContext.getCurrentInstance() returns null. Is there any way to use the FacesContext in a web service.

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  • Constructor versus setter injection

    - by Chris
    Hi, I'm currently designing an API where I wish to allow configuration via a variety of methods. One method is via an XML configuration schema and another method is through an API that I wish to play nicely with Spring. My XML schema parsing code was previously hidden and therefore the only concern was for it to work but now I wish to build a public API and I'm quite concerned about best-practice. It seems that many favor javabean type PoJo's with default zero parameter constructors and then setter injection. The problem I am trying to tackle is that some setter methods implementations are dependent on other setter methods being called before them in sequence. I could write anal setters that will tolerate themselves being called in many orders but that will not solve the problem of a user forgetting to set the appropriate setter and therefore the bean being in an incomplete state. The only solution I can think of is to forget about the objects being 'beans' and enforce the required parameters via constructor injection. An example of this is in the default setting of the id of a component based on the id of the parent components. My Interface public interface IMyIdentityInterface { public String getId(); /* A null value should create a unique meaningful default */ public void setId(String id); public IMyIdentityInterface getParent(); public void setParent(IMyIdentityInterface parent); } Base Implementation of interface: public abstract class MyIdentityBaseClass implements IMyIdentityInterface { private String _id; private IMyIdentityInterface _parent; public MyIdentityBaseClass () {} @Override public String getId() { return _id; } /** * If the id is null, then use the id of the parent component * appended with a lower-cased simple name of the current impl * class along with a counter suffix to enforce uniqueness */ @Override public void setId(String id) { if (id == null) { IMyIdentityInterface parent = getParent(); if (parent == null) { // this may be the top level component or it may be that // the user called setId() before setParent(..) } else { _id = Helpers.makeIdFromParent(parent,getClass()); } } else { _id = id; } } @Override public IMyIdentityInterface getParent() { return _parent; } @Override public void setParent(IMyIdentityInterface parent) { _parent = parent; } } Every component in the framework will have a parent except for the top level component. Using the setter type of injection, then the setters will have different behavior based on the order of the calling of the setters. In this case, would you agree, that a constructor taking a reference to the parent is better and dropping the parent setter method from the interface entirely? Is it considered bad practice if I wish to be able to configure these components using an IoC container? Chris

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  • JTree - Issues with adding of nodes

    - by John
    Hi. Im developing a system that stores courses that participants can apply to. I'm presenting the enrollments in a JTree in the courseadministratorGUI. My problem is that, for every enrollment it's adding a new courseNode. Been trying for many hours, and hope I can now get some advice that will point me in the correct direction. Thank you. private void updateJTree() { for (Category cat : catcontrol.getAllCategoriesList()) { category = new DefaultMutableTreeNode(cat); for (Course c : ccontrol.getAllCourses()) { if (cat.getIdCategory() == c.getIdCategory()) { for (Enrollment e : econtrol.getAllEnrollments()) { if (e.getIdCourse() == c.getIdCourse()) { if (cat.getIdCategory() == c.getIdCategory() && e.getCourse().equals(c)) { root.add(category); } if (c.getIdCourse() == e.getIdCourse()) { course = new DefaultMutableTreeNode(c); category.add(course); enrollment = new DefaultMutableTreeNode(e.getParticipant().getFirstNames()); course.add(enrollment); } } } } } } jTree1.setModel(new DefaultTreeModel(root)); jTree1.addTreeSelectionListener(this); jTree1.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION); }

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  • JTable custom cell renderer to create row header

    - by hhj
    Can somebody please explain how I would create row headers? I already have the data and header texts set in the JTable: all I want to know is how I can use a cell renderer to take that first column (i.e. the row header column) and make it look like the column headers (i.e. the first row). Right now its background is white, so it looks like regular data. I want it to appear gray (or non-opaque I guess??). Oh and it should also not be selectable. Thanks.

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  • Spring MVC 3 - How come @ResponseBody method renders a JSTLView?

    - by Ken Chen
    I have mapped one of my method in one Controller to return JSON object by @ResponseBody. @RequestMapping("/{module}/get/{docId}") public @ResponseBody Map<String, ? extends Object> get(@PathVariable String module, @PathVariable String docId) { Criteria criteria = new Criteria("_id", docId); return genericDAO.getUniqueEntity(module, true, criteria); } However, it redirects me to the JSTLView instead. Say, if the {module} is product and {docId} is 2, then in the console I found: DispatcherServlet with name 'xxx' processing POST request for [/xxx/product/get/2] Rendering view [org.springframework.web.servlet.view.JstlView: name 'product/get/2'; URL [/WEB-INF/views/jsp/product/get/2.jsp]] in DispatcherServlet with name 'xxx' How can that be happened? In the same Controller, I have another method similar to this but it's running fine: @RequestMapping("/{module}/list") public @ResponseBody Map<String, ? extends Object> list(@PathVariable String module, @RequestParam MultiValueMap<String, String> params, @RequestParam(value = "page", required = false) Integer pageNumber, @RequestParam(value = "rows", required = false) Integer recordPerPage) { ... return genericDAO.list(module, criterias, orders, pageNumber, recordPerPage); } Above do returns correctly providing me a list of objects I required. Anyone to help me solve the mystery?

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  • error in midlet while implementing command..

    - by garima
    hi I have imported import com.sun.lwuit.Command; import javax.microedition.midlet.; import javax.microedition.lcdui.; in my code but still the following errors are coming... exitCommand = new Command("Exit", Command.EXIT, 2); //line 1 textbox.addCommand(exitCommand); //line 2 Command.EXIT cannot be resolved.. The method addCommand(Command) in the type Displayable is not applicable for the arguments (Command)

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  • Wicket and Spring Intergation

    - by Vinothbabu
    I have a wicket contact form, and i receive the form object. Now i need to pass this object to Spring Service. package com.mysticcoders.mysticpaste.web.pages; import org.apache.wicket.markup.html.WebPage; import org.apache.wicket.markup.html.form.Form; import org.apache.wicket.markup.html.form.TextField; import org.apache.wicket.markup.html.panel.FeedbackPanel; import com.mysticcoders.mysticpaste.model.Contact; import org.apache.wicket.model.CompoundPropertyModel; import com.mysticcoders.mysticpaste.services.IContact; public class FormPage extends WebPage { private Contact contact; private IContact icontact; public FormPage() { // Add a FeedbackPanel for displaying our messages FeedbackPanel feedbackPanel = new FeedbackPanel("feedback"); add(feedbackPanel); Form<Object> form = new Form<Object>("contactForm", new CompoundPropertyModel<Object>(contact)) { private static final long serialVersionUID = 1L; protected void onSubmit(Contact contact) { icontact.saveContact(contact); } }; form.add(new TextField<Object>("name")); form.add(new TextField<Object>("email")); form.add(new TextField<Object>("country")); form.add(new TextField<Object>("age")); add(form); // add a simple text field that uses Input's 'text' property. Nothing // can go wrong here } } I am pretty much sure that we need to do something with application-context xml where i may need to wire out. My Application-context.xml <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd"> <bean id="WicketApplication" class="com.mysticcoders.mysticpaste.web.pages.WicketApplication" /> </beans> My Question is simple. What should i do which can make my onSubmit method call the Spring Service? Could someone let me know what needs to modified in my Application-context.xml so that once the form gets submitted, it contacts the Spring Service class.

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  • UI not updated while using ProgressMonitorInputStream in Swing to monitor compressed file decompress

    - by Bozhidar Batsov
    I'm working on swing application that relies on an embedded H2 database. Because I don't want to bundle the database with the app(the db is frequently updated and I want new users of the app to start with a recent copy), I've implemented a solution which downloads a compressed copy of the db the first time the application is started and extracts it. Since the extraction process might be slow I've added a ProgressMonitorInputStream to show to progress of the extraction process - unfortunately when the extraction starts, the progress dialog shows up but it's not updated at all. It seems like to events are getting through to the event dispatch thread. Here is the method: public static String extractDbFromArchive(String pathToArchive) { if (SwingUtilities.isEventDispatchThread()) { System.out.println("Invoking on event dispatch thread"); } // Get the current path, where the database will be extracted String currentPath = System.getProperty("user.home") + File.separator + ".spellbook" + File.separator; LOGGER.info("Current path: " + currentPath); try { //Open the archive FileInputStream archiveFileStream = new FileInputStream(pathToArchive); // Read two bytes from the stream before it used by CBZip2InputStream for (int i = 0; i < 2; i++) { archiveFileStream.read(); } // Open the gzip file and open the output file CBZip2InputStream bz2 = new CBZip2InputStream(new ProgressMonitorInputStream( null, "Decompressing " + pathToArchive, archiveFileStream)); FileOutputStream out = new FileOutputStream(ARCHIVED_DB_NAME); LOGGER.info("Decompressing the tar file..."); // Transfer bytes from the compressed file to the output file byte[] buffer = new byte[1024]; int len; while ((len = bz2.read(buffer)) > 0) { out.write(buffer, 0, len); } // Close the file and stream bz2.close(); out.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException ex) { ex.printStackTrace(); } try { TarInputStream tarInputStream = null; TarEntry tarEntry; tarInputStream = new TarInputStream(new ProgressMonitorInputStream( null, "Extracting " + ARCHIVED_DB_NAME, new FileInputStream(ARCHIVED_DB_NAME))); tarEntry = tarInputStream.getNextEntry(); byte[] buf1 = new byte[1024]; LOGGER.info("Extracting tar file"); while (tarEntry != null) { //For each entry to be extracted String entryName = currentPath + tarEntry.getName(); entryName = entryName.replace('/', File.separatorChar); entryName = entryName.replace('\\', File.separatorChar); LOGGER.info("Extracting entry: " + entryName); FileOutputStream fileOutputStream; File newFile = new File(entryName); if (tarEntry.isDirectory()) { if (!newFile.mkdirs()) { break; } tarEntry = tarInputStream.getNextEntry(); continue; } fileOutputStream = new FileOutputStream(entryName); int n; while ((n = tarInputStream.read(buf1, 0, 1024)) > -1) { fileOutputStream.write(buf1, 0, n); } fileOutputStream.close(); tarEntry = tarInputStream.getNextEntry(); } tarInputStream.close(); } catch (Exception e) { } currentPath += "db" + File.separator + DB_FILE_NAME; if (!currentPath.isEmpty()) { LOGGER.info("DB placed in : " + currentPath); } return currentPath; } This method gets invoked on the event dispatch thread (SwingUtilities.isEventDispatchThread() returns true) so the UI components should be updated. I haven't implemented this as an SwingWorker since I need to wait for the extraction anyways before I can proceed with the initialization of the program. This method get invoked before the main JFrame of the application is visible. I don't won't a solution based on SwingWorker + property changed listeners - I think that the ProgressMonitorInputStream is exactly what I need, but I guess I'm not doing something right. I'm using Sun JDK 1.6.18. Any help would be greatly appreciated.

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  • How to use a jar in Unity3D?

    - by Dima Goltsman
    I have a jar library that i created. It can be integrated in any android app and it works like this: String token="<SOME_TOKEN>"; DeviceIdentifier edDevice = new DeviceIdentifier( this.getApplicationContext(),token); edDevice.update(); DeviceIdentifier class os a class in the jar. now i want to make that jar work with Unity3d, i searched the web and couldn't find anything what is the correct way to integrate it?

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  • Counting viable sublist lengths from an array.

    - by Ben B.
    This is for a genetic algorithm fitness function, so it is important I can do this as efficiently as possible, as it will be repeated over and over. Lets say there is a function foo(int[] array) that returns true if the array is a "good" array and false if the array is a "bad" array. What makes it good or bad does not matter here. Given the full array [1,6,8,9,5,11,45,16,9], lets say that subarray [1,6,8] is a "good" array and [9,5,11,45] is a "good" array. Furthermore [5,11,45,16,9] is a "good" array, and also the longest "good" subarray. Notice that while [9,5,11,45] is a "good" array, and [5,11,45,16,9] is a "good" array, [9,5,11,45,16,9] is a "bad" array. We wants the length counts of all "good" arrays, but not subarrays of "good" arrays. Furthermore, as described above, a "good" array might begin in the middle of another "good" array, but the combination of the two might be a "bad" array.

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  • How to differentiate between time to live and time to idle in ehcache

    - by Jacques René Mesrine
    The docs on ehache says: timeToIdleSeconds: Sets the time to idle for an element before it expires. i.e. The maximum amount of time between accesses before an element expires timeToLiveSeconds: Sets the time to live for an element before it expires. i.e. The maximum time between creation time and when an element expires. I understand timeToIdleSeconds But does it means that after the creation & first access of a cache item, the timeToLiveSeconds is not applicable anymore ?

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  • How to customize android analog clock widget through configuration screen

    - by michJ
    I'm trying to develop my own analog clock widget on the home screen. It's based on the stock ICS analog clock widget, but when added to the homescreen, my widget opens a configuration screen first. On this screen you can choose the color you want the clock to be (through a colorpicker dialog). You also see a preview of the clock in the chosen color on this screen. (See picture). My problem is changing the color of the widget on the home screen to the chosen color (when you hit the apply button). I have three .png files that I use for the dial, hour hand and minute hand. I color them using this code in my widgetconfig class: Drawable dial = getResources().getDrawable(R.drawable.clockbackground); dial.setColorFilter(color, PorterDuff.Mode.MULTIPLY); //hour Drawable hour = getResources().getDrawable(R.drawable.hourhand); hour.setColorFilter(color, PorterDuff.Mode.MULTIPLY); //minute Drawable min = getResources().getDrawable(R.drawable.minutehand); min.setColorFilter(color, PorterDuff.Mode.MULTIPLY); // clock AnalogClock clockpreview = (AnalogClock) findViewById(R.id.ACconfig); clockpreview.setBackgroundDrawable(dial); This works fine because I can find the AnalogClock since it's in the layout xml file of the configuration screen, which I set in the OnCreate() through setContentView(). The problem is that for the clock widget on my screen I have to use RemoteViews. So I tried setting the new background of the clock widget through RemoteViews. But RemoteViews seems too limited to do this. I need something like setTextViewText() but then for the background of my analog clock widget, like for example: RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.clockwidget); views.setAnalogClockBackgroundDrawable(dial); The clock widget background seems sort of unchangeable. How can I recolor my clockwidget on homescreen in widgetconfig class? There must be a way because it seems so easy to do at first... My project consists of the widget config class and clockwidget class, widgetconfig.xml, clockwidget.xml, and widget_info.xml (for appwidgetprovider).

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  • Correct way to persist Quartz triggers

    - by davioooh
    I'm quite new to Quartz and now I need to schedule some jobs in Spring Web App. I know about Spring + Quartz integration (I'm using Spring v 3.1.1) but I'm wondering if it's the right way to follow. In particular I need to persist my scheduled tasks in a DB so I can re-initialize them when application is restarted. Are there some utilities provided by Spring scheduling wrapper to do this? Can you suggest me some "well known" approach to follow?

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  • Draw a position from a 2d Array on respected canvas location

    - by Anon
    Background: I have two 2d arrays. Each index within each 2d array represents a tile which is drawn on a square canvas suitable for 8 x 8 tiles. The first 2d array represents the ground tiles and is looped and drawn on the canvas using the following code: //Draw the map from the land 2d array map = new Canvas(mainFrame, 20, 260, 281, 281); for(int i=0; i < world.length; i++){ for(int j=0; j < world[i].length; j++){ for(int x=0; x < 280; x=x+35){ for(int y=0; y < 280; y=y+35){ Point p = new Point(x,y); map.add(new RectangleObject(p,35,35,Colour.green)); } } } } This creates a grid of green tiles 8 x 8 across as intended. The second 2d array represents the position on the ground. This 2d array has everyone of its indexes as null apart from one which is comprised of a Person class. Problem I am unsure of how I can draw the position on the grid. I was thinking of a similar loop, so it draws over the previous 2d array another set of 64 tiles. Only this time they are all transparent but the one tile which isn't null. In other words, the tile where Person is located. I wanted to use a search throughout the loop using a comparative if statement along the lines of if(!(world[] == null)){ map.add(new RectangleObject(p,35,35,Colour.red));} However my knowledge is limited and I am confused on how to implement it.

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  • Design for tagging system in GAE-J

    - by tempy
    I need a simple tagging system in GAE-J. As I see it, the entity that is being tagged should have a collection of keys referring to the tags with which it's associated. A tag entity should simply contain the tag string itself, and a collection of keys pointing to the entities associated with the tag. When an entity's list of tags is altered, the system will create a new tag if the tag is unknown, and then append the entity's key to that tag's key collection. If the tag already exists, then the entity's key is simply appended to the tag's key collection. This seems relatively straight-forward and uncontroversial to me, but I would like some feedback on this design, just to be sure.

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  • JBoss Clustered Service that sends emails from txt file

    - by michael lucas
    I need a little push in the right direction. Here's my problem: I have to create an ultra-reliable service that sends email messages to clients whose addresses are stored in txt file on FTP server. Single txt file may contain unlimited number of entries. Most often the file contains about 300,000 entries. Service exposes interface with just two simple methods: TaskHandle sendEmails(String ftpFilePath); ProcessStatus checkProcessStatus(TaskHandle taskHandle); Method sendEmails() returns TaskHandle by which we can ask for ProcessStatus. For such a service to be reliable clustering is necessary. Processing single txt file might take a long time. Restarting one node in a cluster should have no impact on sending emails. We use JBoss AS 4.2.0 which comes with a nice HASingletonController that ensure one instance of service is running at given time. But once a fail-over happens, the second service should continue work from where the first one stopped. How can I share state between nodes in a cluster in such a way that leaves no possibility of sending some emails twice?

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  • Can the JVM recover from an OutOfMemoryError without a restart

    - by askullhead
    Can the JVM recover from an OutOfMemoryError without a restart if it gets a chance to run the GC before more object allocation requests come in? Do the various JVM implementations differ in this aspect? EDIT: My question was about the JVM recovering and not the user program trying to recover by catching the error. In other words if an OOME is thrown in an application server (jboss/websphere/..) do I have to restart it? Or can I let it run if further requests seem to work without a problem. Sorry if that wan't clear.

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