code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.loops;
  
  /*
   * 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
   * Checks for responsiveness of locks to timeouts. Runs under the
   * assumption that ITERS computations require more than TIMEOUT msecs
   * to complete, which seems to be a safe assumption for another
   * decade.
   */
  
  import java.util.concurrent.*;
  import java.util.concurrent.locks.*;
  import java.util.*;
  
  public final class TimeoutMutexLoops {
      static final ExecutorService pool = Executors.newCachedThreadPool();
      static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
      static boolean print = false;
      static final int ITERS = Integer.MAX_VALUE;
      static final long TIMEOUT = 100;
  
      public static void main(String[] args) throws Exception {
          int maxThreads = 100;
          if (args.length > 0)
              maxThreads = Integer.parseInt(args[0]);
  
          print = true;
  
          for (int i = 1; i <= maxThreads; i += (i+1) >>> 1) {
              System.out.print("Threads: " + i);
              new MutexLoop(i).test();
              Thread.sleep(TIMEOUT);
          }
          pool.shutdown();
      }
  
      static final class MutexLoop implements Runnable {
          private int v = rng.next();
          private volatile boolean completed;
          private volatile int result = 17;
          private final Mutex lock = new Mutex();
          private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
          private final CyclicBarrier barrier;
          private final int nthreads;
          MutexLoop(int nthreads) {
              this.nthreads = nthreads;
              barrier = new CyclicBarrier(nthreads+1, timer);
          }
  
          final void test() throws Exception {
              for (int i = 0; i < nthreads; ++i)
                  pool.execute(this);
              barrier.await();
              Thread.sleep(TIMEOUT);
              lock.lock();
              barrier.await();
              if (print) {
                  long time = timer.getTime();
                  double secs = (double) time / 1000000000.0;
                  System.out.println("\t " + secs + "s run time");
              }
  
              if (completed)
                  throw new Error("Some thread completed instead of timing out");
              int r = result;
              if (r == 0) // avoid overoptimization
                  System.out.println("useless result: " + r);
          }
  
          public final void run() {
              try {
                  barrier.await();
                  int sum = v;
                  int x = 0;
                  int n = ITERS;
                  do {
                      if (!lock.tryLock(TIMEOUT, TimeUnit.MILLISECONDS))
                          break;
                      try {
                          v = x = LoopHelpers.compute1(v);
                      }
                      finally {
                          lock.unlock();
                      }
                      sum += LoopHelpers.compute2(x);
                  } while (n-- > 0);
                  if (n <= 0)
                      completed = true;
                  barrier.await();
                  result += sum;
              }
              catch (Exception ie) {
                  return;
              }
          }
      }
  
  }
  