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  1. import java.util.ArrayList;
  2. import java.util.List;
  3.  
  4. public class VolatileTest {
  5.     public static void main(final String[] args) throws InterruptedException {
  6.         final long start = System.currentTimeMillis();
  7.         final int max = 5000;
  8.         final int maxThreads = 2;
  9.         for (int i = 0; i < max; i++) {
  10.             final List<Thread> threadList = new ArrayList<>();
  11.             for (int j = 0; j < maxThreads; j++) {
  12.                 threadList.add(new Thread(new Runnable() {
  13.                     @Override
  14.                     public void run() {
  15.                         do_something();
  16.                     }
  17.                 }));
  18.             }
  19.             for (final Thread thread : threadList)
  20.                 thread.start();
  21.             for (final Thread thread : threadList)
  22.                 thread.join();
  23.         }
  24.         final long end = System.currentTimeMillis();
  25.         System.out.println((end - start) + " ms");
  26.         // for 2 threads:
  27.         //   16407 ms (w/o volatile counter)
  28.         //  176203 ms
  29.         //     1 thread
  30.         //   10687 ms (w/o volatile counter)
  31.         //  154345 ms
  32.         // intel snb 3.3 ghz, 2x2 cores
  33.     }
  34.  
  35.     static int value = 1; // add volatile for volatile run
  36.     static final int maxcount = 100_000_000;
  37.  
  38.     public static int do_something() {
  39.         int sum = 0;
  40.         for (int i = 0; i < maxcount; i++) {
  41.             sum += value;
  42.         }
  43.         return sum;
  44.     }
  45. }
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https://ideone.com/O4kN8s
language:
Java (12.0.1)
created:
12 years ago
visibility:
public

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