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Java Newsletters Archive: 180

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=== [ The Java FAQ Daily Tips, weekly publication ] ===

Issue No: 180 14 August 2003
14070 subscribers

Foreword: Excuse me for possible mistakes. English is not native language for me.

In this issue:
  • 1. What are additional types of GC do exist in the J2SE platform, version 1.4.2?
  • 2. With 1.3.1 we got 4GB heaps on Solaris, why can't I get this to work on Windows?
  • 3. Latest posts on our message board
  • 4. Link to Java FAQ

  • Hello dear friends!

    Tip 1

    Question: What are additional types of GC do exist in the J2SE platform, version 1.4.2?

    Answer:
    1. The throughput collector: this collector uses a parallel version of the young generation collector. It is used if the -XX:+UseParallelGC option is passed on the command line. The tenured generation collector is the same as the default collector.

    2. The concurrent low pause collector: this collector is used if the -XX:+UseConcMarkSweepGC is passed on the command line. The concurrent collector is used to collect the tenured generation and does most of the collection concurrently with the execution of the application. The application is paused for short periods during the collection. A parallel version of the young generation copying collector is used with the concurrent collector if the combination -XX:+UseConcMarkSweepGC -XX:+UseParNewGC is passed on the command line.
    This kind is also known as concurrent GC.

    3. The incremental (sometimes called train) low pause collector: this collector is used only if -Xincgc is passed on the command line. By careful bookkeeping, the incremental garbage collector collects just a portion of the tenured generation at each minor collection, trying to spread the large pause of a major collection over many minor collections. However, it is even slower than the default tenured generation collector when considering overall throughput.

    Important! -XX:+UseParallelGC should not be used with -XX:+UseConcMarkSweepGC. The argument parsing in the J2SE platform, version 1.4.2 should only allow legal combinations of command line options for garbage collectors, but earlier releases may not detect all illegal combinations and the results for illegal combinations are unpredictable.

    Also important to remember: always try default GC before using additional GCs!

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    Tip 2

    Question: With 1.3.1 we got 4GB heaps on Solaris, why can't I get this to work on Windows?

    Answer: It's due to fragmentation of the address space. After Windows has loaded all its stuff, plus the java dlls, the largest available continuous chunk of addresses for the heap is about 1.4-1.6G on Win/NT. Might be smaller on Win/98.

    If you really need more space they can try rebasing java.exe and the JDK dlls higher. But that won't buy you much (maybe a couple hundred meg).
    from the Java Hotspot Virtual Machine FAQ:
    http://java.sun.com/docs/hotspot/PerformanceFAQ.html


    Latest posts on our message board
    Compositing(image and movie) in Java

    I would like to do some compositing in Java. Currently I'm using QuickTime for Java to do it. It is very easy. However I always get some runtime exception when I execute the program. So I want to switch to pure Java. I want to play a movie as the background, probably using JMF. Then do some animation with some images and text in front of the movie. Is this possible? Any advice or sample program?

    Thanks in advance.
    please help here

    JTabbedPane and focus issue

    Maybe I'm just doing things a bit different than anyone else and I'm wrong. Here's the deal: I have a focus traversal policy for each frame in my app. When I used a personally-created subclass of JTabbedPane it was trying to set focus on a component on a non-visible tab. So I fixed that problem by not allowing focus to go to non-visible tab panels.

    Now I want, on a tab change, to set focus on the first focusable component of the new tab. But at the time I get a change event to hook this call the old tab is still visible and the second one isn't.

    So my first fix...
    thread continues here

    How to realize my project

    Hi,
    I’m new on java and i should do a project to create an application to design Workflow on thin client (IE6) or a software and use Java Web Start. The design is base on the state-chart diagram. All the information concerning items (position, size) will be store under lotus Notes Documents.
    Each item (state, chart relations) will have different values selected from list. Each list will be fill in with informations descended from data contains under Lotus Notes documents.
    thread continues here


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