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  • Will this ever result in a stack overflow error?

    - by David
    Will incrementing the instance variables of an object ever lead to a stack overflow error? For example: This method (java) will cause a stack overflow error: class StackOverflow { public static void StackOverflow (int x) { System.out.println (x) ; StackOverflow(x+1) ; } public static void main (String[]arg) { StackOverflow (0) ; } but will this?: (..... is a gap that i've put in to shorten the code. its long enough as it is.) import java.util.*; class Dice { String name ; int x ; int[] sum ; .... public Dice (String name) { this.name = name ; this.x = 0 ; this.sum = new int[7] ; } .... public static void main (String[] arg) { Dice a1 = new Dice ("a1") ; for (int i = 0; i<6000000; i++) { a1.roll () ; printDice(a1) ; } } .... public void roll () { this.x = randNum(1, this.sum.length) ; this.sum[x] ++ ; } public static int randNum (int a, int b) { Random random = new Random() ; int c = (b-a) ; int randomNumber = ((random.nextInt(c)) + a) ; return randomNumber ; } public static void printDice (Dice Dice) { System.out.println (Dice.name) ; System.out.println ("value: "+Dice.x) ; printValues (Dice) ; } public static void printValues (Dice Dice) { for (int i = 0; i<Dice.sum.length; i++) System.out.println ("#of "+i+"'s: "+Dice.sum[i]) ; } } The above doesn't currently cause a stack overflow error but could i get it too if i changed this line in main: for (int i = 0; i<6000000; i++) so that instead of 6 million something sufficiently high were there?

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  • JNI cached jclass global reference variables being garbage collected?

    - by bubbadoughball
    I'm working in the JNI Invocation API, calling into Java from C. I have some upfront initialization to cache 30+ Java classes into global references. The results of FindClass are passed into NewGlobalRef to acquire a global reference to the class. I'm caching these class variables to reuse them later. I have 30+ global references to classes (and 30+ global methodIDs for the class constructors). In the following sample, I've removed exception handling as well as JNI invocation for the purpose of shortening the code snippet. My working code has exception checks after every JNI call and I'm running with -Xcheck:jni. Here's the snippet: jclass aClass; jclass bClass; jmethodID aCtor; jmethodID bCtor; void getGlobalRef(const char* clazz, jclass* globalClass) { jclass local = (*jenv)->FindClass(jenv,clazz); if (local) { *globalClass = (jclass) (*jenv)->NewGlobalRef(jenv,local); (*jenv)->DeleteLocalRef(jenv,local); } } methodID getMethodID(jclass clazz, const char* method, const char* sig) { return (*jenv)->GetMethodID(jenv,clazz,method,sig); } void initializeJNI() { getGlobalRef("MyProj/Testclass1", &aclass); getGlobalRef("MyProj/Testclass2", &bclass); . . aCtor = getMethodID(aclass,"<init>","()V"); bCtor = getMethodID(bclass,"<init>","(I)V"); } The initializeJNI() function sets the global references for jclasses and method IDs for constructors as well as some jfieldID's and some initialization of C data structures. After initialization, when I call into a JNI function using some of the cached jclasses and ctor jmethodIDs, I get a bad global or local reference calling reported from the -Xcheck:jni. In gdb, I break at the last line of initializeJNI(), and print all jclasses and jmethodIDs and the ones causing problems look to have been turned into garbage or garbage-collected (i.e. 0x00 or 0x06). Is it possible for global references to be gc'ed? Any suggestions?

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  • Find out what variable is throwing a NullPointerException programatically

    - by Hectoret
    I know I can find out if a variable is null in Java using these techniques: if (var==null) - too much work try { ... } catch (NullPointerException e) { ...} - it tells me what line is throwing the exception using the debugger - by hand, too slow Consider this line of code: if (this.superSL.items.get(name).getSource().compareTo(VIsualShoppingList.Source_EXTRA)==0) { I would like to know if there's a generic way to find out programatically what variable (not just the line) is throwing the NullPointerException in a certain area of code. In the example, knowing that

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  • Hadoop: Processing large serialized objects

    - by restrictedinfinity
    I am working on development of an application to process (and merge) several large java serialized objects (size of order GBs) using Hadoop framework. Hadoop stores distributes blocks of a file on different hosts. But as deserialization will require the all the blocks to be present on single host, its gonna hit the performance drastically. How can I deal this situation where different blocks have to cant be individually processed, unlike text files ?

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  • Progress bar while applet loads

    - by Dan
    OK so, let's say I have a Java applet that takes a while to load (~5 secs). It's getting the mysql-connector.jar and it's loading. Well.. instead of the gray box with the coffee logo... can I make it have a simple progress bar with the percent? Thanks.

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  • int datatype in 64bit JVM. Is it more "inefficient" than long?

    - by Zwei Steinen
    I heard that using shorts on 32bit system is just more inefficient than using ints. Is this the same for ints on a 64bit system? Python recently(?) basically merged ints with long and has basically a single datatype long, right? If you are sure that your app. will only run on 64bit then, is it even conceivable (potentially a good idea) to use long for everything in Java?

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  • JBoss AS 5 "Failed to add Resource"

    - by Mark
    Hello - We are stumped and looking for advice.. Were running: jdk1.6.0_20 , jboss-5.1.0.GA, messaging-2.0.0.BETA4 And trying to add a Topic or Queue but we are getting this error: Failed to add Resource: java.lang.IllegalStateException:Failed to find template for: TopicTemplate any advice?

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  • question on rss feed application

    - by molleman
    Hello Guys i just want to create a simple application that will allow a user to input a url to a rss feed and display the contents to a user. what would be a good java library to enable me to read rss feeds? cheers

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  • Image.createImage problem in J2ME

    - by Michael
    Hi All, I tried this on J2ME try { Image immutableThumb = Image.createImage( temp, 0, temp.length); } catch (Exception ex) { System.out.println(ex); } I hit this error: java.lang.IllegalArgumentException: How do I solve this?

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  • Multicore programming: what's necessary to do it?

    - by Casey
    I have a quadcore processor and I would really like to take advantage of all those cores when I'm running quick simulations. The problem is I'm only familiar with the small Linux cluster we have in the lab and I'm using Vista at home. What sort of things do I want to look into for multicore programming with C or Java? What is the lingo that I want to google? Thanks for the help.

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  • Projects with browsable source using dependency injection w/ guice?

    - by André
    I often read about dependency injection and I did research on google and I understand in theory what it can do and how it works, but I'd like to see an actual code base using it (Java/guice would be preferred). Can anyone point me to an open source project, where I can see, how it's really used? I think browsing the code and seeing the whole setup shows me more than the ususal snippets in the introduction articles you find around the web. Thanks in advance!

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  • assigning a specific record in a ResultSet to a variable

    - by kilhra
    Hi I want to retrieve a set of records from a database, do a rs.next() and then assign the result of this to a variable to pass to a method that will use this record, in the same way that I would without assigning it to a variable and passing it to a method is there any way to do this? I'm using JAVA (1.5)

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  • Multiple sessions for one user?

    - by ganuke
    Hi I have host web application which is developed using java and jsp. In client side each client give five ajax calls to the server to retrieve data from the server in every 30 seconds. My problem is can one user who use one browser to log in to the system have multiple session at a time. Reason is when i use the tool to use monitor the firewall I can see more than 10 sessions are active for one IP. How this can happen? any comments

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  • I am faceing problem with this error of struts application.

    - by Sanjeev
    I am using My-eclipse and doing a struts project there is no syntax error but on starting tomcat server the following error appear in console. java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory and javax.servlet.UnavailableException: Parsing error processing resource path jndi:/localhost/strutspro/WEB-INF/struts-config.xml any idea whats the problem.

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  • Simple logger, how to ?

    - by Andrei Ciobanu
    Hello, I want to write a default Logger for my application. Currently I am using the default Java API Class Logger . I was wondering if it's possible to format my logs to look somthing like this: [level] [dd:MM:YYYY] [hh:mm:ss] message The logger should also be able to print the messages into the System.out and into a file ? Where should I look for this functionality ? Can you please give me some code snippets ?

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