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programming:java:multithreading [2023/11/01 07:31] – removed - external edit (Unknown date) 127.0.0.1programming:java:multithreading [2023/11/01 07:31] (current) – ↷ Page moved from camunda:programming:java:multithreading to programming:java:multithreading skipidar
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 +===== Multithreading =====
 +^What ^Where ^
 +|Introduction | [[http://www.vogella.com/articles/JavaConcurrency/article.html|vogella]] |
 +|Whereever possible use the safe Structures from | [[http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/package-summary.html|concurrent package]] |
 +
 +
 +=== PitFalls ===
 +  - Do not use **TimeStamps** to synchronize Threads. Therere can be more than 1 action every millisecond - what to do with equal TimeStamps?
 +
 +
 +=== Concurrent Package ===
 +Das [[http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/package-summary.html|Concurrent Package]] bietet viele fertige Multithreading Klassen.
 +
 +
 +^Class ^ What ^
 +| [[http://docs.oracle.com/javase/1.4.2/docs/api/java/util/Timer.html|Timer]] | Can execute TimerTasks(Runnables) after a Timeout. Can be canceled only once. |
 +| [[http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/FutureTask.html|Future]]  | Can compute something asynchronously. The result, when ready, is available throught get() |
 +
 +
 +=== ForkJoin ===
 +A framework to execute parallel task. The mechanism is [[http://www.cs.washington.edu/homes/djg/teachingMaterials/spac/grossmanSPAC_forkJoinFramework.html|described here]].
 +
 +
 +[[http://help.eclipse.org/helios/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Freference%2Fapi%2Forg%2Feclipse%2Fswt%2Fwidgets%2FDisplay.html|Display.readAndDispatch()]]
 +<sxh java>
 +//A nice way to stop the UI thread, in order to wait for a job, without blocking the UI Jobs coming from other Threads
 +while(job.getResult()==null) {
 +  Display.getDefault().readAndDispatch();
 +}
 +</sxh>
 +
 +=== Try-Catch is Bypassed in nested threads ===
 +On every thread there should be an own Exception-handling. Putting a new Thread creation into try-catch block won't catch the Exceptions.
 +
 +<sxh java>
 + //ATTENTION: the exception is not catched!
 + try{
 + Runnable r = new Runnable() {
 +
 + @Override
 + public void run() {
 + System.out.println("Thread");
 +
 + Display.getDefault().syncExec(new Runnable() {
 +                     @Override
 +                     public void run() {
 +                     System.out.println("ThreadGUI");
 +                     throw new NullPointerException();
 +                     }
 +                 });
 +
 + }
 + };
 +
 + Thread t = new Thread(r);
 + t.start();
 +
 + }catch(NullPointerException e){
 + //nothing
 + }
 +
 + System.out.println("Ende");
 +</sxh>