code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.concurrent.FutureTask;
  
  /*
   * Written by Doug Lea with assistance from members of JCP JSR-166
   * Expert Group and released to the public domain, as explained at
   * http://creativecommons.org/licenses/publicdomain
   */
  
  /*
   * @test
   * @bug 4486658
   * @compile -source 1.5 CancelledFutureLoops.java
   * @run main/timeout=2000 CancelledFutureLoops
   * @summary Checks for responsiveness of futures to cancellation.
   * Runs under the assumption that ITERS computations require more than
   * TIMEOUT msecs to complete.
   */
  
  import java.util.concurrent.*;
  import java.util.concurrent.locks.*;
  import java.util.*;
  
  public final class CancelledFutureLoops {
      static final ExecutorService pool = Executors.newCachedThreadPool();
      static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
      static boolean print = false;
      static final int ITERS = 1000000;
      static final long TIMEOUT = 100;
  
      public static void main(String[] args) throws Exception {
          int maxThreads = 5;
          if (args.length > 0)
              maxThreads = Integer.parseInt(args[0]);
  
          print = true;
  
          for (int i = 2; i <= maxThreads; i += (i+1) >>> 1) {
              System.out.print("Threads: " + i);
              try {
                  new FutureLoop(i).test();
              }
              catch(BrokenBarrierException bb) {
                  // OK; ignore
              }
              catch(ExecutionException ee) {
                  // OK; ignore
              }
              Thread.sleep(TIMEOUT);
          }
          pool.shutdown();
          if (! pool.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS))
              throw new Error();
      }
  
      static final class FutureLoop implements Callable {
          private int v = rng.next();
          private final ReentrantLock lock = new ReentrantLock();
          private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
          private final CyclicBarrier barrier;
          private final int nthreads;
          FutureLoop(int nthreads) {
              this.nthreads = nthreads;
              barrier = new CyclicBarrier(nthreads+1, timer);
          }
  
          final void test() throws Exception {
              Future[] futures = new Future[nthreads];
              for (int i = 0; i < nthreads; ++i)
                  futures[i] = pool.submit(this);
  
              barrier.await();
              Thread.sleep(TIMEOUT);
              boolean tooLate = false;
              for (int i = 1; i < nthreads; ++i) {
                  if (!futures[i].cancel(true))
                      tooLate = true;
                  // Unbunch some of the cancels
                  if ( (i & 3) == 0)
                      Thread.sleep(1 + rng.next() % 10);
              }
  
              Object f0 = futures[0].get();
              if (!tooLate) {
                  for (int i = 1; i < nthreads; ++i) {
                      if (!futures[i].isDone() || !futures[i].isCancelled())
                          throw new Error("Only one thread should complete");
                  }
              }
              else
                  System.out.print("(cancelled too late) ");
  
              long endTime = System.nanoTime();
              long time = endTime - timer.startTime;
              if (print) {
                  double secs = (double)(time) / 1000000000.0;
                  System.out.println("\t " + secs + "s run time");
              }
  
          }
  
          public final Object call() throws Exception {
              barrier.await();
              int sum = v;
              int x = 0;
              int n = ITERS;
              while (n-- > 0) {
                  lock.lockInterruptibly();
                  try {
                      v = x = LoopHelpers.compute1(v);
                  }
                  finally {
                      lock.unlock();
                  }
                  sum += LoopHelpers.compute2(LoopHelpers.compute2(x));
              }
              return new Integer(sum);
          }
      }
  
  }
  