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  • Is it ever OK to throw a java.lang.Error?

    - by Abhijeet Kashnia
    I have a plugin module that goes into a web application. If the module does not load correctly, it does not make sense for the web application to go on, and the web application should probably not load at all, we would prefer this module to initialize correctly always. If I were to throw a runtime exception, it would get into the logs, and just get ignored since the application will continue anyway, and the end users would never know... I know that errors are meant to be thrown only under exceptional conditions, and they generally have to do with situations that the system cannot recover from, but what would you do in such a situation?

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  • Best way to identify and dispose locked thread in java.

    - by Bala R
    I have to call a function 3rd party module on a new thread. From what I've seen, the call either completes quickly if everything went well or it just hangs for ever locking up the thread. What's a good way to start the thread and make the call and wait for a few secs and if the thread is still alive, then assuming it's locked up, kill (or stop or abandon) the thread without using any deprecated methods. I have something like this for now, but I'm not sure if this is the best way to do it and I want to avoid calling Thread.stop() as it's deprecated. Thanks. private void foo() throws Exception { Runnable runnable = new Runnable() { @Override public void run() { // stuff that could potentially lock up the thread. } }; Thread thread; thread = new Thread(runnable); thread.start(); thread.join(3500); if (thread.isAlive()) { thread.stop(); throw new Exception(); } }

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  • Does the java JFC hash table use seperate chaining resolution? Can I traverse each list in the table

    - by Matt
    I have written a program to store a bunch of strings in a JFC hash table. There are defiantly collisions going on, but I don't really know how it is handling them. My ultimate goal is to print the number of occurrences of each string in the table, and traversing the bucket or list would work nicely. Or maybe counting the collisions? Or do you have another idea of how I could get a count of the elements?

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  • Is an ArrayList automatically declared static in Java, if it is an instance variable?

    - by Alex
    I'm trying to do something like this: private class aClass { private ArrayList<String> idProd; aClass(ArrayList<String> prd) { this.idProd=new ArrayList<String>(prd); } public ArrayList<String> getIdProd() { return this.idProd; } } So if I have multiple instances of ArrayLIst<String> (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); } Will all of the aClass objects return st3 if I access the method getIdProd() for each of them(obj1..obj3)? Is an ArrayList as an instance variable automatically declared static?

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  • Where to store global variables like file paths in java ?

    - by Jules Olléon
    In my application I use some icons. Where should I store the path of the directory containing those icons ? The icons are used in different classes so it doesn't really make sense to store them in one of those classes in particular. I read that global variables are evil, but is it acceptable to use a class (eg Commons) containing only public static final fields to store this king of data ? What solution is used in professional applications ?

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  • Compiling CSS to SWF server side Java, What is the best practice?

    - by DataSurfer
    My project allows users to create custom css for our flex app. In regards to compiling the CSS into SWFs on the server side: Should I use the flex2.compiler.css.Compiler class in mxmlc-3.5.0.12683.jar? Or Should I invoke mxmlc from Runtime.getRuntime().exec()? The css.Compiler class is not very well documented. Does anyone have any examples that use this? For the Runtime exec method, what is the best way to package mxmlc into the maven build so its available to the server at runtime?

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  • Java - Unknown characters passing as [a-zA-z0-9]*?

    - by Twodordan
    Hello, I'm no expert in regex but I need to parse some input I have no control over, and make sure I filter away any strings that don't have A-z and/or 0-9. When I run this, Pattern p = Pattern.compile("^[a-zA-Z0-9]*$"); //fixed typo if(!p.matcher(gottenData).matches()) System.out.println(someData); //someData contains gottenData certain spaces + an unknown symbol somehow slip through the filter (gottenData is the red rectangle): In case you're wondering, it DOES also display Text, it's not all like that. For now, I don't mind the [?] as long as it also contains some string along with it. Please help. [EDIT] as far as I can tell from the (very large) input, the [?]'s are either white spaces either nothing at all; maybe there's some sort of encoding issue, also perhaps something to do with #text nodes (input is xml)

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  • Can someone explain this java interface to me please?

    - by Karl Patrick
    I realize that the method run must be declared because its declared in the runnable interface. But my question comes when this class runs how is the Thread object allowed if there is no import call to a particular package? how does runnable know anything about Thread or its methods? does the runnable interface extend the thread class? Obviously i dont understand interfaces very well. thanks in advance. class PrimeFinder implements Runnable{ public long target; public long prime; public boolean finished = false; public Thread runner; PrimeFinder(long inTarget){ target = inTarget; if(runner == null){ runner = new Thread(this); runner.start() } } public void run(){ } }

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  • How to fill a two Dimensional ArrayList in java with Integers?

    - by eNetik
    I have to create a 2d array with unknown size. So I have decided to go with a 2d ArrayList the problem is I'm not sure how to initialize such an array or store information. Say I have the following data 0 connects 1 2 connects 3 4 connects 5 ....etc up to a vast amount of random connections and I want to insert true(1) into [0][1], true(1) into [2][3], true(1) into [4][5]. Can the array automatically update the column/rows for me Any help is appreciated thanks

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  • Java CRTP: Works for container but not for methods?

    - by Daniel
    I have a baseclass with a protected static ArrayList. I want to have a seperate ArrayList for each kind of subclass that extends this baseclass. This is when I applied CRTP: public class BaseExample<T> { protected static ArrayList<Integer> data = new ArrayList<Integer>(); } This works just fine. However, when I try to implement the following static method in the same base class, it doesn't adhere to CRTP: public static void clear() { data.clear(); } For example: class SubExample extends BaseExample<SubExample> { // insertion methods accessing 'data' field // these work fine :) } SubExample.clear(); // does not seem to clear data container Do I need to somehow explicitly specify T in my baseclass clear method? Note: These are all pure static classes.

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  • How to find all initializations of instance variables in a Java package?

    - by Hank Gay
    I'm in the midst of converting a legacy app to Spring. As part of the transition, we're converting our service classes from an "instantiate new ones whenever you need one" style to a Springleton style, so I need a way to make sure they don't have any state. I'm comfortable on the *nix command-line, and I have access to IntelliJ (this strikes me as a good fit for Structural Search and Replace, if I could figure out how to use it), and I could track down an Eclipse install, if that would help. I just want to make absolutely sure I've found all the possible problems. UPDATE: Sorry for the confusion. I don't have a problem finding places where the old constructor was being called. What I'm looking for is a "bullet-proof" why to search all 100+ service classes for any sort of internal state. The most obvious one I could think of (and the only one I've really found so far) is cases where we use memoization in the classes, so they have instance variables that get initialized internally instead of via Spring. This means that when the same Springleton gets used for different requests, data can leak between them. Thanks.

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  • Java FMJ is not cross platfrom ? How can it be fixed ?

    - by Stackfan
    I was trying to use FMJ (for windows/linux/mac). Where JMF was not working for me (so decided to work with FMJ as it is cross platfaorm). But when ever i am trying FMJ it never works, where you can see the difference in the screen shot. ex: http://i.imgur.com/AjcJh.png Thanks & Regards Note: I have two camera connected in the same PC and Flash detects always both of them without any issue. But FMJ is never working ?????.

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  • Save Java frame as a Microsoft Word or PDF document?

    - by Jason
    I am working on a billing program - right now when you click the appropriate button it generates a frame that shows the various charges etc, basically an invoice. Is there a way to give the user an option of saving that frame as a document, either Microsoft Word, Microsoft Works or PDF?

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  • How to proceed jpeg Image file size after read--rotate-write operations in Java?

    - by zamska
    Im trying to read a JPEG image as BufferedImage, rotate and save it as another jpeg image from file system. But there is a problem : after these operations I cannot proceed same file size. Here the code //read Image BufferedImage img = ImageIO.read(new File(path)); //rotate Image BufferedImage rotatedImage = new BufferedImage(image.getHeight(), image.getWidth(), BufferedImage.TYPE_3BYTE_BGR); Graphics2D g2d = (Graphics2D) rotatedImage.getGraphics(); g2d.rotate(Math.toRadians(PhotoConstants.ROTATE_LEFT)); int height=-rotatedImage.getHeight(null); g2d.drawImage(image, height, 0, null); g2d.dispose(); //Write Image Iterator iter = ImageIO.getImageWritersByFormatName("jpeg"); ImageWriter writer = (ImageWriter)iter.next(); // instantiate an ImageWriteParam object with default compression options ImageWriteParam iwp = writer.getDefaultWriteParam(); try { FileImageOutputStream output = null; iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT); iwp.setCompressionQuality(0.98f); // an integer between 0 and 1 // 1 specifies minimum compression and maximum quality File file = new File(path); output = new FileImageOutputStream(file); writer.setOutput(output); IIOImage iioImage = new IIOImage(image, null, null); writer.write(null, iioImage, iwp); output.flush(); output.close(); writer.dispose(); Is it possible to access compressionQuality parameter of original jpeg image in the beginning. when I set 1 to compression quality, the image gets bigger size. Otherwise I set 0.9 or less the image gets smaller size. How can i proceed the image size after these operations? Thank you,

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  • What's the easiest way to add Java servlets to a WAMP configured machine?

    - by Rhubarb
    I have WAMP installed on my local machine and am looking to serve up charts using jFree's Eastwood charting, which requires me to use servlets. So basically I will insert images with src tags that have URLs pointing to my servlet on the same machine. What's the easiest way to enable servlets on the same machine? Do I need to install a servlet server on a different port? Or is there a way to integrate it into WAMP?

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

    - by Alex
    I'm trying to do something like this: private class aClass { private ArrayList<String> idProd; aClass(ArrayList<String> prd) { this.idProd=new ArrayList<String>(prd); } public ArrayList<String> getIdProd() { return this.idProd; } } So if I have multiple instances of ArrayLIst<String> (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); } Will all of the aClass objects return st3 if I access the method getIdProd() for each of them(obj1..obj3)? Is an ArrayList as an instance variable automatically declared static?

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  • How Two Programs Can Talk To Each Other In Java?

    - by Arnon
    My first time here... I want to ?reduce? the CPU usage/ROM usage/RAM usage - in general ?speaking?, all system resources that my App use - how doesn't? :) For this reason i want to split the preferences window from the rest of the application, and let the preferences window to run as ?independent? program. The preferences program ?should? write to a Property file(not a problem at all) and to send a "update signal" to the main program - which mean, to call the update method(that i wrote) that found in the Main class. How can i call the update method in the Main program from the preferences program? Or in the other hand... There is a way to build preferences window that take system resources just when it's appear? Is this approach - of separating programs and let them talk to each other(somehow) - is a right approach for speeding up my programs? tnx

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  • How do I close a file after catching an IOException in java?

    - by DimDom
    All, I am trying to ensure that a file I have open with BufferedReader is closed when I catch an IOException, but it appears as if my BufferedReader object is out of scope in the catch block. public static ArrayList readFiletoArrayList(String fileName, ArrayList fileArrayList) { fileArrayList.removeAll(fileArrayList); try { //open the file for reading BufferedReader fileIn = new BufferedReader(new FileReader(fileName)); // add line by line to array list, until end of file is reached // when buffered reader returns null (todo). while(true){ fileArrayList.add(fileIn.readLine()); } }catch(IOException e){ fileArrayList.removeAll(fileArrayList); fileIn.close(); return fileArrayList; //returned empty. Dealt with in calling code. } } Netbeans complains that it "cannot find symbol fileIn" in the catch block, but I want to ensure that in the case of an IOException that the Reader gets closed. How can I do that without the ugliness of a second try/catch construct around the first? Any tips or pointers as to best practise in this situation is appreciated,

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