code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.concurrent.BlockingQueue;
  
  /*
   * 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 6805775 6815766
   * @run main OfferDrainToLoops 300
   * @summary Test concurrent offer vs. drainTo
   */
  
  import java.util.*;
  import java.util.concurrent.*;
  import java.util.concurrent.atomic.*;
  
  @SuppressWarnings({"unchecked", "rawtypes", "deprecation"})
  public class OfferDrainToLoops {
      final long testDurationMillisDefault = 10L * 1000L;
      final long testDurationMillis;
  
      OfferDrainToLoops(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 {
          test(new LinkedBlockingQueue());
          test(new LinkedBlockingQueue(2000));
          test(new LinkedBlockingDeque());
          test(new LinkedBlockingDeque(2000));
          test(new ArrayBlockingQueue(2000));
          //test(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 test(final BlockingQueue 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;
  
          /** 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() {
                  long c = 0;
                  for (long i = 0; ! quittingTime(i); i++) {
                      if (q.offer(c)) {
                          if ((++c % 1024) == 0) {
                              approximateCount.getAndAdd(1024);
                              while (approximateCount.get() > 10000)
                                  Thread.yield();
                          }
                      } else {
                          Thread.yield();
                      }}}};
  
          Thread drainer = new CheckedThread("drainer") {
              protected void realRun() {
                  final Random rnd = getRandom();
                  while (! quittingTime()) {
                      List list = new ArrayList();
                      int n = rnd.nextBoolean() ?
                          q.drainTo(list) :
                          q.drainTo(list, 100);
                      approximateCount.getAndAdd(-n);
                      equal(list.size(), n);
                      for (int j = 0; j < n - 1; j++)
                          equal((Long) list.get(j) + 1L, list.get(j + 1));
                      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:
                          Long[] a = (Long[]) q.toArray(new Long[0]);
                          int n = a.length;
                          for (int j = 0; j < n - 1; j++) {
                              check(a[j] < a[j+1]);
                              check(a[j] != null);
                          }
                          break;
                      }
                      Thread.yield();
                  }}};
  
          for (Thread thread : new Thread[] { offerer, drainer, 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 OfferDrainToLoops(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");}
  }
  