code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.concurrent.ConcurrentQueues;
  
  /*
   * 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 6785442
   * @summary Benchmark that tries to GC-tenure head, followed by
   * many add/remove operations.
   * @run main GCRetention 12345
   */
  
  import java.util.concurrent.ArrayBlockingQueue;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.LinkedBlockingDeque;
  import java.util.concurrent.LinkedBlockingQueue;
  //import java.util.concurrent.LinkedTransferQueue;
  import java.util.concurrent.PriorityBlockingQueue;
  import java.util.LinkedList;
  import java.util.PriorityQueue;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  import java.util.Queue;
  import java.util.Map;
  
  public class GCRetention {
      // Suitable for benchmarking.  Overriden by args[0] for testing.
      int count = 1024 * 1024;
  
      final Map<String,String> results = new ConcurrentHashMap<String,String>();
  
      Collection<Queue<Boolean>> queues() {
          List<Queue<Boolean>> queues = new ArrayList<Queue<Boolean>>();
          queues.add(new ConcurrentLinkedQueue<Boolean>());
          queues.add(new ArrayBlockingQueue<Boolean>(count, false));
          queues.add(new ArrayBlockingQueue<Boolean>(count, true));
          queues.add(new LinkedBlockingQueue<Boolean>());
          queues.add(new LinkedBlockingDeque<Boolean>());
          queues.add(new PriorityBlockingQueue<Boolean>());
          queues.add(new PriorityQueue<Boolean>());
          queues.add(new LinkedList<Boolean>());
  //        queues.add(new LinkedTransferQueue<Boolean>());
  
          // Following additional implementations are available from:
          // http://gee.cs.oswego.edu/dl/concurrency-interest/index.html
          // queues.add(new SynchronizedLinkedListQueue<Boolean>());
  
          // Avoid "first fast, second slow" benchmark effect.
          Collections.shuffle(queues);
          return queues;
      }
  
      void prettyPrintResults() {
          List<String> classNames = new ArrayList<String>(results.keySet());
          Collections.sort(classNames);
          int maxClassNameLength = 0;
          int maxNanosLength = 0;
          for (String name : classNames) {
              if (maxClassNameLength < name.length())
                  maxClassNameLength = name.length();
              if (maxNanosLength < results.get(name).length())
                  maxNanosLength = results.get(name).length();
          }
          String format = String.format("%%%ds %%%ds nanos/item%%n",
                                        maxClassNameLength, maxNanosLength);
          for (String name : classNames)
              System.out.printf(format, name, results.get(name));
      }
  
      void test(String[] args) {
          if (args.length > 0)
              count = Integer.valueOf(args[0]);
          // Warmup
          for (Queue<Boolean> queue : queues())
              test(queue);
          results.clear();
          for (Queue<Boolean> queue : queues())
              test(queue);
  
          prettyPrintResults();
      }
  
      void test(Queue<Boolean> q) {
          long t0 = System.nanoTime();
          for (int i = 0; i < count; i++)
              check(q.add(Boolean.TRUE));
          System.gc();
          System.gc();
          Boolean x;
          while ((x = q.poll()) != null)
              equal(x, Boolean.TRUE);
          check(q.isEmpty());
  
          for (int i = 0; i < 10 * count; i++) {
              for (int k = 0; k < 3; k++)
                  check(q.add(Boolean.TRUE));
              for (int k = 0; k < 3; k++)
                  if (q.poll() != Boolean.TRUE)
                      fail();
          }
          check(q.isEmpty());
  
          String className = q.getClass().getSimpleName();
          long elapsed = System.nanoTime() - t0;
          int nanos = (int) ((double) elapsed / (10 * 3 * count));
          results.put(className, String.valueOf(nanos));
      }
  
      //--------------------- 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 GCRetention().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");}
  }
  