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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.concurrent.ConcurrentHashMap;
  4.  
  5. /* Name of the class has to be "Main" only if the class is public. */
  6. class Ideone implements Runnable
  7. {
  8.  
  9.     private static ConcurrentHashMap<String, String> chm = null;
  10.     private static final Object syncloc = new Object();
  11.     private static boolean go = false;
  12.  
  13.     public static void setConcurrentHashMap(ConcurrentHashMap<String, String> c) {
  14.         System.out.println("Setting CHM " + System.identityHashCode(c));
  15.         chm = c;
  16.     }
  17.  
  18.     public static ConcurrentHashMap<String, String> getConcurrentHashMap() {
  19.         return chm;
  20.     }
  21.  
  22.     public void run() {
  23.         try {
  24.             synchronized (syncloc) {
  25.                 while (!go) {
  26.                     syncloc.wait();
  27.                 }
  28.             }
  29.             ConcurrentHashMap<String, String> mymap = getConcurrentHashMap();
  30.             if (mymap == null) {
  31.                 mymap = new ConcurrentHashMap<String, String>();
  32.                 setConcurrentHashMap(mymap);
  33.             }
  34.         } catch (InterruptedException ie) {
  35.             ie.printStackTrace();
  36.         }
  37.     }
  38.  
  39.  
  40.     public static void main (String[] args) throws java.lang.Exception
  41.     {
  42.  
  43.         Thread[] threads = new Thread[5];
  44.         for (int i = 0; i < threads.length; i++) {
  45.             threads[i] = new Thread(new Ideone());
  46.             threads[i].start();
  47.         }
  48.         synchronized (syncloc) {
  49.             go = true;
  50.             syncloc.notifyAll();
  51.         }
  52.         for (Thread t : threads) {
  53.             t.join();
  54.         }
  55.     }
  56. }
Success #stdin #stdout 0.06s 381824KB
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Standard input is empty
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Setting CHM 15013136
Setting CHM 30545452
Setting CHM 15416452
Setting CHM 16329928
Setting CHM 30013691
https://ideone.com/PKvCSd
language:
Java (HotSpot 12)
created:
11 years ago
visibility:
public

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