code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.concurrent.ConcurrentQueues;
  
  /*
   * Copyright 2005-2008 Sun Microsystems, Inc.  All Rights Reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
   * CA 95054 USA or visit www.sun.com if you need additional information or
   * have any questions.
   */
  
  /*
   * @test
   * @bug 6316155 6595669 6871697 6868712
   * @summary Test concurrent offer vs. remove
   * @run main OfferRemoveLoops 300
   * @author Martin Buchholz
   */
  
  import java.util.*;
  import java.util.concurrent.*;
  import java.util.concurrent.atomic.*;
  
  @SuppressWarnings({"unchecked", "rawtypes", "deprecation"})
  public class OfferRemoveLoops {
      final long testDurationMillisDefault = 10L * 1000L;
      final long testDurationMillis;
  
      OfferRemoveLoops(String[] args) {
          testDurationMillis = (args.length > 0) ?
              Long.valueOf(args[0]) : testDurationMillisDefault;
      }
  
      void checkNotContainsNull(Iterable it) {
          for (Object x : it)
              check(x != null);
      }
  
      void test(String[] args) throws Throwable {
          testQueue(new LinkedBlockingQueue(10));
          testQueue(new LinkedBlockingQueue());
          testQueue(new LinkedBlockingDeque(10));
          testQueue(new LinkedBlockingDeque());
          testQueue(new ArrayBlockingQueue(10));
          testQueue(new PriorityBlockingQueue(10));
          testQueue(new ConcurrentLinkedQueue());
          //testQueue(new LinkedTransferQueue());
      }
  
      private static Random seeder = new Random();
      private static ThreadLocal<Random> local = new ThreadLocal<Random>() {
          protected Random initialValue() {
              return new Random(seeder.nextLong());
          }
      };
  
      Random getRandom() {
          //return ThreadLocalRandom.current();
          return local.get();
      }
  
      void testQueue(final Queue q) throws Throwable {
          System.out.println(q.getClass().getSimpleName());
          final long testDurationNanos = testDurationMillis * 1000L * 1000L;
          final long quittingTimeNanos = System.nanoTime() + testDurationNanos;
          final long timeoutMillis = 10L * 1000L;
          final int maxChunkSize = 1042;
          final int maxQueueSize = 10 * maxChunkSize;
  
          /** Poor man's bounded buffer. */
          final AtomicLong approximateCount = new AtomicLong(0L);
  
          abstract class CheckedThread extends Thread {
              CheckedThread(String name) {
                  super(name);
                  setDaemon(true);
                  start();
              }
              /** Polls for quitting time. */
              protected boolean quittingTime() {
                  return System.nanoTime() - quittingTimeNanos > 0;
              }
              /** Polls occasionally for quitting time. */
              protected boolean quittingTime(long i) {
                  return (i % 1024) == 0 && quittingTime();
              }
              abstract protected void realRun();
              public void run() {
                  try { realRun(); } catch (Throwable t) { unexpected(t); }
              }
          }
  
          Thread offerer = new CheckedThread("offerer") {
              protected void realRun() {
                  final long chunkSize = getRandom().nextInt(maxChunkSize) + 2;
                  long c = 0;
                  for (long i = 0; ! quittingTime(i); i++) {
                      if (q.offer(Long.valueOf(c))) {
                          if ((++c % chunkSize) == 0) {
                              approximateCount.getAndAdd(chunkSize);
                              while (approximateCount.get() > maxQueueSize)
                                  Thread.yield();
                          }
                      } else {
                          Thread.yield();
                      }}}};
  
          Thread remover = new CheckedThread("remover") {
              protected void realRun() {
                  final long chunkSize = getRandom().nextInt(maxChunkSize) + 2;
                  long c = 0;
                  for (long i = 0; ! quittingTime(i); i++) {
                      if (q.remove(Long.valueOf(c))) {
                          if ((++c % chunkSize) == 0) {
                              approximateCount.getAndAdd(-chunkSize);
                          }
                      } else {
                          Thread.yield();
                      }
                  }
                  q.clear();
                  approximateCount.set(0); // Releases waiting offerer thread
              }};
  
          Thread scanner = new CheckedThread("scanner") {
              protected void realRun() {
                  final Random rnd = getRandom();
                  while (! quittingTime()) {
                      switch (rnd.nextInt(3)) {
                      case 0: checkNotContainsNull(q); break;
                      case 1: q.size(); break;
                      case 2: checkNotContainsNull
                              (Arrays.asList(q.toArray(new Long[0])));
                          break;
                      }
                      Thread.yield();
                  }}};
  
          for (Thread thread : new Thread[] { offerer, remover, scanner }) {
              thread.join(timeoutMillis + testDurationMillis);
              if (thread.isAlive()) {
                  System.err.printf("Hung thread: %s%n", thread.getName());
                  failed++;
                  for (StackTraceElement e : thread.getStackTrace())
                      System.err.println(e);
                  // Kludge alert
                  thread.stop();
                  thread.join(timeoutMillis);
              }
          }
      }
  
      //--------------------- Infrastructure ---------------------------
      volatile int passed = 0, failed = 0;
      void pass() {passed++;}
      void fail() {failed++; Thread.dumpStack();}
      void fail(String msg) {System.err.println(msg); fail();}
      void unexpected(Throwable t) {failed++; t.printStackTrace();}
      void check(boolean cond) {if (cond) pass(); else fail();}
      void equal(Object x, Object y) {
          if (x == null ? y == null : x.equals(y)) pass();
          else fail(x + " not equal to " + y);}
      public static void main(String[] args) throws Throwable {
          new OfferRemoveLoops(args).instanceMain(args);}
      public void instanceMain(String[] args) throws Throwable {
          try {test(args);} catch (Throwable t) {unexpected(t);}
          System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
          if (failed > 0) throw new AssertionError("Some tests failed");}
  }
  