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
   */
  
  import java.util.*;
  import java.util.concurrent.*;
  
  /*
   * @test
   * @bug 6805775 6815766
   * @summary Check weak consistency of concurrent queue iterators
   */
  
  @SuppressWarnings({"unchecked", "rawtypes"})
  public class IteratorWeakConsistency {
  
      void test(String[] args) throws Throwable {
          test(new LinkedBlockingQueue());
          test(new LinkedBlockingQueue(20));
          test(new LinkedBlockingDeque());
          test(new LinkedBlockingDeque(20));
          test(new ConcurrentLinkedQueue());
          //test(new LinkedTransferQueue());
          // Other concurrent queues (e.g. ArrayBlockingQueue) do not
          // currently have weakly consistent iterators.
          // test(new ArrayBlockingQueue(20));
      }
  
      void test(Queue q) throws Throwable {
          // TODO: make this more general
          for (int i = 0; i < 10; i++)
              q.add(i);
          Iterator it = q.iterator();
          q.poll();
          q.poll();
          q.poll();
          q.remove(7);
          List list = new ArrayList();
          while (it.hasNext())
              list.add(it.next());
          equal(list, Arrays.asList(0, 3, 4, 5, 6, 8, 9));
          check(! list.contains(null));
          System.out.printf("%s: %s%n",
                            q.getClass().getSimpleName(),
                            list);
      }
  
      //--------------------- 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);}
      static Class<?> thisClass = new Object(){}.getClass().getEnclosingClass();
      public static void main(String[] args) throws Throwable {
          new IteratorWeakConsistency().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");}
  }
  