code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.tck;
  
  /*
   * 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
   * Other contributors include Andrew Wright, Jeffrey Hayes,
   * Pat Fisher, Mike Judd.
   */
  
  import junit.framework.*;
  import java.util.*;
  import java.util.concurrent.*;
  import static java.util.concurrent.TimeUnit.MILLISECONDS;
  import java.io.*;
  
  public class SynchronousQueueTest extends JSR166TestCase {
  
      public static void main(String[] args) {
          junit.textui.TestRunner.run (suite());
      }
  
      public static Test suite() {
          return new TestSuite(SynchronousQueueTest.class);
      }
  
      /**
       * A SynchronousQueue is both empty and full
       */
      public void testEmptyFull() {
          SynchronousQueue q = new SynchronousQueue();
          assertTrue(q.isEmpty());
          assertEquals(0, q.size());
          assertEquals(0, q.remainingCapacity());
          assertFalse(q.offer(zero));
      }
  
      /**
       * A fair SynchronousQueue is both empty and full
       */
      public void testFairEmptyFull() {
          SynchronousQueue q = new SynchronousQueue(true);
          assertTrue(q.isEmpty());
          assertEquals(0, q.size());
          assertEquals(0, q.remainingCapacity());
          assertFalse(q.offer(zero));
      }
  
      /**
       * offer(null) throws NPE
       */
      public void testOfferNull() {
          try {
              SynchronousQueue q = new SynchronousQueue();
              q.offer(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * add(null) throws NPE
       */
      public void testAddNull() {
          try {
              SynchronousQueue q = new SynchronousQueue();
              q.add(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * offer fails if no active taker
       */
      public void testOffer() {
          SynchronousQueue q = new SynchronousQueue();
          assertFalse(q.offer(one));
      }
  
      /**
       * add throws ISE if no active taker
       */
      public void testAdd() {
          try {
              SynchronousQueue q = new SynchronousQueue();
              assertEquals(0, q.remainingCapacity());
              q.add(one);
              shouldThrow();
          } catch (IllegalStateException success) {}
      }
  
      /**
       * addAll(null) throws NPE
       */
      public void testAddAll1() {
          try {
              SynchronousQueue q = new SynchronousQueue();
              q.addAll(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * addAll(this) throws IAE
       */
      public void testAddAllSelf() {
          try {
              SynchronousQueue q = new SynchronousQueue();
              q.addAll(q);
              shouldThrow();
          } catch (IllegalArgumentException success) {}
      }
  
      /**
       * addAll of a collection with null elements throws NPE
       */
      public void testAddAll2() {
          try {
              SynchronousQueue q = new SynchronousQueue();
              Integer[] ints = new Integer[1];
              q.addAll(Arrays.asList(ints));
              shouldThrow();
          } catch (NullPointerException success) {}
      }
      /**
       * addAll throws ISE if no active taker
       */
      public void testAddAll4() {
          try {
              SynchronousQueue q = new SynchronousQueue();
              Integer[] ints = new Integer[1];
              for (int i = 0; i < 1; ++i)
                  ints[i] = new Integer(i);
              q.addAll(Arrays.asList(ints));
              shouldThrow();
          } catch (IllegalStateException success) {}
      }
  
      /**
       * put(null) throws NPE
       */
      public void testPutNull() throws InterruptedException {
          try {
              SynchronousQueue q = new SynchronousQueue();
              q.put(null);
              shouldThrow();
          } catch (NullPointerException success) {}
       }
  
      /**
       * put blocks interruptibly if no active taker
       */
      public void testBlockingPut() throws InterruptedException {
          Thread t = new Thread(new CheckedInterruptedRunnable() {
              public void realRun() throws InterruptedException {
                  SynchronousQueue q = new SynchronousQueue();
                  q.put(zero);
              }});
  
          t.start();
          Thread.sleep(SHORT_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
      /**
       * put blocks waiting for take
       */
      public void testPutWithTake() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue();
          Thread t = new Thread(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  int added = 0;
                  try {
                      while (true) {
                          q.put(added);
                          ++added;
                      }
                  } catch (InterruptedException success) {
                      assertTrue(added == 1);
                  }
              }});
  
          t.start();
          Thread.sleep(SHORT_DELAY_MS);
          assertEquals(0, q.take());
          Thread.sleep(SHORT_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
      /**
       * timed offer times out if elements not taken
       */
      public void testTimedOffer() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue();
          Thread t = new Thread(new CheckedInterruptedRunnable() {
              public void realRun() throws InterruptedException {
                  assertFalse(q.offer(new Object(), SHORT_DELAY_MS, MILLISECONDS));
                  q.offer(new Object(), LONG_DELAY_MS, MILLISECONDS);
              }});
  
          t.start();
          Thread.sleep(SMALL_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
  
      /**
       * take blocks interruptibly when empty
       */
      public void testTakeFromEmpty() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue();
          Thread t = new Thread(new CheckedInterruptedRunnable() {
              public void realRun() throws InterruptedException {
                  q.take();
              }});
  
          t.start();
          Thread.sleep(SHORT_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
  
      /**
       * put blocks interruptibly if no active taker
       */
      public void testFairBlockingPut() throws InterruptedException {
          Thread t = new Thread(new CheckedInterruptedRunnable() {
              public void realRun() throws InterruptedException {
                  SynchronousQueue q = new SynchronousQueue(true);
                  q.put(zero);
              }});
  
          t.start();
          Thread.sleep(SHORT_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
      /**
       * put blocks waiting for take
       */
      public void testFairPutWithTake() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue(true);
          Thread t = new Thread(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  int added = 0;
                  try {
                      while (true) {
                          q.put(added);
                          ++added;
                      }
                  } catch (InterruptedException success) {
                      assertTrue(added == 1);
                  }
              }});
  
          t.start();
          Thread.sleep(SHORT_DELAY_MS);
          assertEquals(0, q.take());
          Thread.sleep(SHORT_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
      /**
       * timed offer times out if elements not taken
       */
      public void testFairTimedOffer() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue(true);
          Thread t = new Thread(new CheckedInterruptedRunnable() {
              public void realRun() throws InterruptedException {
                  assertFalse(q.offer(new Object(), SHORT_DELAY_MS, MILLISECONDS));
                  q.offer(new Object(), LONG_DELAY_MS, MILLISECONDS);
              }});
  
          t.start();
          Thread.sleep(SMALL_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
  
      /**
       * take blocks interruptibly when empty
       */
      public void testFairTakeFromEmpty() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue(true);
          Thread t = new Thread(new CheckedInterruptedRunnable() {
              public void realRun() throws InterruptedException {
                  q.take();
              }});
  
          t.start();
          Thread.sleep(SHORT_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
      /**
       * poll fails unless active taker
       */
      public void testPoll() {
          SynchronousQueue q = new SynchronousQueue();
          assertNull(q.poll());
      }
  
      /**
       * timed pool with zero timeout times out if no active taker
       */
      public void testTimedPoll0() throws InterruptedException {
          SynchronousQueue q = new SynchronousQueue();
          assertNull(q.poll(0, MILLISECONDS));
      }
  
      /**
       * timed pool with nonzero timeout times out if no active taker
       */
      public void testTimedPoll() throws InterruptedException {
          SynchronousQueue q = new SynchronousQueue();
          assertNull(q.poll(SHORT_DELAY_MS, MILLISECONDS));
      }
  
      /**
       * Interrupted timed poll throws InterruptedException instead of
       * returning timeout status
       */
      public void testInterruptedTimedPoll() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue();
          Thread t = new Thread(new CheckedInterruptedRunnable() {
              public void realRun() throws InterruptedException {
                  q.poll(SMALL_DELAY_MS, MILLISECONDS);
              }});
  
          t.start();
          Thread.sleep(SHORT_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
      /**
       *  timed poll before a delayed offer fails; after offer succeeds;
       *  on interruption throws
       */
      public void testTimedPollWithOffer() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue();
          Thread t = new Thread(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  assertNull(q.poll(SHORT_DELAY_MS, MILLISECONDS));
                  assertSame(zero, q.poll(LONG_DELAY_MS, MILLISECONDS));
                  try {
                      q.poll(LONG_DELAY_MS, MILLISECONDS);
                      shouldThrow();
                  } catch (InterruptedException success) {}
              }});
  
          t.start();
          Thread.sleep(SMALL_DELAY_MS);
          assertTrue(q.offer(zero, SHORT_DELAY_MS, MILLISECONDS));
          t.interrupt();
          t.join();
      }
  
      /**
       * Interrupted timed poll throws InterruptedException instead of
       * returning timeout status
       */
      public void testFairInterruptedTimedPoll() throws InterruptedException {
          Thread t = new Thread(new CheckedInterruptedRunnable() {
              public void realRun() throws InterruptedException {
                  SynchronousQueue q = new SynchronousQueue(true);
                  q.poll(SMALL_DELAY_MS, MILLISECONDS);
              }});
  
          t.start();
          Thread.sleep(SHORT_DELAY_MS);
          t.interrupt();
          t.join();
      }
  
      /**
       *  timed poll before a delayed offer fails; after offer succeeds;
       *  on interruption throws
       */
      public void testFairTimedPollWithOffer() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue(true);
          Thread t = new Thread(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  assertNull(q.poll(SHORT_DELAY_MS, MILLISECONDS));
                  assertSame(zero, q.poll(LONG_DELAY_MS, MILLISECONDS));
                  try {
                      q.poll(LONG_DELAY_MS, MILLISECONDS);
                      threadShouldThrow();
                  } catch (InterruptedException success) {}
              }});
  
          t.start();
          Thread.sleep(SMALL_DELAY_MS);
          assertTrue(q.offer(zero, SHORT_DELAY_MS, MILLISECONDS));
          t.interrupt();
          t.join();
      }
  
  
      /**
       * peek returns null
       */
      public void testPeek() {
          SynchronousQueue q = new SynchronousQueue();
          assertNull(q.peek());
      }
  
      /**
       * element throws NSEE
       */
      public void testElement() {
          SynchronousQueue q = new SynchronousQueue();
          try {
              q.element();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       * remove throws NSEE if no active taker
       */
      public void testRemove() {
          SynchronousQueue q = new SynchronousQueue();
          try {
              q.remove();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       * remove(x) returns false
       */
      public void testRemoveElement() {
          SynchronousQueue q = new SynchronousQueue();
          assertFalse(q.remove(zero));
          assertTrue(q.isEmpty());
      }
  
      /**
       * contains returns false
       */
      public void testContains() {
          SynchronousQueue q = new SynchronousQueue();
          assertFalse(q.contains(zero));
      }
  
      /**
       * clear ensures isEmpty
       */
      public void testClear() {
          SynchronousQueue q = new SynchronousQueue();
          q.clear();
          assertTrue(q.isEmpty());
      }
  
      /**
       * containsAll returns false unless empty
       */
      public void testContainsAll() {
          SynchronousQueue q = new SynchronousQueue();
          Integer[] empty = new Integer[0];
          assertTrue(q.containsAll(Arrays.asList(empty)));
          Integer[] ints = new Integer[1]; ints[0] = zero;
          assertFalse(q.containsAll(Arrays.asList(ints)));
      }
  
      /**
       * retainAll returns false
       */
      public void testRetainAll() {
          SynchronousQueue q = new SynchronousQueue();
          Integer[] empty = new Integer[0];
          assertFalse(q.retainAll(Arrays.asList(empty)));
          Integer[] ints = new Integer[1]; ints[0] = zero;
          assertFalse(q.retainAll(Arrays.asList(ints)));
      }
  
      /**
       * removeAll returns false
       */
      public void testRemoveAll() {
          SynchronousQueue q = new SynchronousQueue();
          Integer[] empty = new Integer[0];
          assertFalse(q.removeAll(Arrays.asList(empty)));
          Integer[] ints = new Integer[1]; ints[0] = zero;
          assertFalse(q.containsAll(Arrays.asList(ints)));
      }
  
  
      /**
       * toArray is empty
       */
      public void testToArray() {
          SynchronousQueue q = new SynchronousQueue();
          Object[] o = q.toArray();
          assertEquals(o.length, 0);
      }
  
      /**
       * toArray(a) is nulled at position 0
       */
      public void testToArray2() {
          SynchronousQueue q = new SynchronousQueue();
          Integer[] ints = new Integer[1];
          assertNull(ints[0]);
      }
  
      /**
       * toArray(null) throws NPE
       */
      public void testToArray_BadArg() {
          SynchronousQueue q = new SynchronousQueue();
          try {
              Object o[] = q.toArray(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
  
      /**
       * iterator does not traverse any elements
       */
      public void testIterator() {
          SynchronousQueue q = new SynchronousQueue();
          Iterator it = q.iterator();
          assertFalse(it.hasNext());
          try {
              Object x = it.next();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       * iterator remove throws ISE
       */
      public void testIteratorRemove() {
          SynchronousQueue q = new SynchronousQueue();
          Iterator it = q.iterator();
          try {
              it.remove();
              shouldThrow();
          } catch (IllegalStateException success) {}
      }
  
      /**
       * toString returns a non-null string
       */
      public void testToString() {
          SynchronousQueue q = new SynchronousQueue();
          String s = q.toString();
          assertNotNull(s);
      }
  
  
      /**
       * offer transfers elements across Executor tasks
       */
      public void testOfferInExecutor() {
          final SynchronousQueue q = new SynchronousQueue();
          ExecutorService executor = Executors.newFixedThreadPool(2);
  
          executor.execute(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  assertFalse(q.offer(one));
                  assertTrue(q.offer(one, MEDIUM_DELAY_MS, MILLISECONDS));
                  assertEquals(0, q.remainingCapacity());
              }});
  
          executor.execute(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  Thread.sleep(SMALL_DELAY_MS);
                  assertSame(one, q.take());
              }});
  
          joinPool(executor);
      }
  
      /**
       * poll retrieves elements across Executor threads
       */
      public void testPollInExecutor() {
          final SynchronousQueue q = new SynchronousQueue();
          ExecutorService executor = Executors.newFixedThreadPool(2);
          executor.execute(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  assertNull(q.poll());
                  assertSame(one, q.poll(MEDIUM_DELAY_MS, MILLISECONDS));
                  assertTrue(q.isEmpty());
              }});
  
          executor.execute(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  Thread.sleep(SHORT_DELAY_MS);
                  q.put(one);
              }});
  
          joinPool(executor);
      }
  
      /**
       * a deserialized serialized queue is usable
       */
      public void testSerialization() throws Exception {
          SynchronousQueue q = new SynchronousQueue();
          ByteArrayOutputStream bout = new ByteArrayOutputStream(10000);
          ObjectOutputStream out = new ObjectOutputStream(new BufferedOutputStream(bout));
          out.writeObject(q);
          out.close();
  
          ByteArrayInputStream bin = new ByteArrayInputStream(bout.toByteArray());
          ObjectInputStream in = new ObjectInputStream(new BufferedInputStream(bin));
          SynchronousQueue r = (SynchronousQueue)in.readObject();
          assertEquals(q.size(), r.size());
          while (!q.isEmpty())
              assertEquals(q.remove(), r.remove());
      }
  
      /**
       * drainTo(null) throws NPE
       */
      public void testDrainToNull() {
          SynchronousQueue q = new SynchronousQueue();
          try {
              q.drainTo(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * drainTo(this) throws IAE
       */
      public void testDrainToSelf() {
          SynchronousQueue q = new SynchronousQueue();
          try {
              q.drainTo(q);
              shouldThrow();
          } catch (IllegalArgumentException success) {}
      }
  
      /**
       * drainTo(c) of empty queue doesn't transfer elements
       */
      public void testDrainTo() {
          SynchronousQueue q = new SynchronousQueue();
          ArrayList l = new ArrayList();
          q.drainTo(l);
          assertEquals(q.size(), 0);
          assertEquals(l.size(), 0);
      }
  
      /**
       * drainTo empties queue, unblocking a waiting put.
       */
      public void testDrainToWithActivePut() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue();
          Thread t = new Thread(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  q.put(new Integer(1));
              }});
  
          t.start();
          ArrayList l = new ArrayList();
          Thread.sleep(SHORT_DELAY_MS);
          q.drainTo(l);
          assertTrue(l.size() <= 1);
          if (l.size() > 0)
              assertEquals(l.get(0), new Integer(1));
          t.join();
          assertTrue(l.size() <= 1);
      }
  
      /**
       * drainTo(null, n) throws NPE
       */
      public void testDrainToNullN() {
          SynchronousQueue q = new SynchronousQueue();
          try {
              q.drainTo(null, 0);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * drainTo(this, n) throws IAE
       */
      public void testDrainToSelfN() {
          SynchronousQueue q = new SynchronousQueue();
          try {
              q.drainTo(q, 0);
              shouldThrow();
          } catch (IllegalArgumentException success) {}
      }
  
      /**
       * drainTo(c, n) empties up to n elements of queue into c
       */
      public void testDrainToN() throws InterruptedException {
          final SynchronousQueue q = new SynchronousQueue();
          Thread t1 = new Thread(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  q.put(one);
              }});
  
          Thread t2 = new Thread(new CheckedRunnable() {
              public void realRun() throws InterruptedException {
                  q.put(two);
              }});
  
          t1.start();
          t2.start();
          ArrayList l = new ArrayList();
          Thread.sleep(SHORT_DELAY_MS);
          q.drainTo(l, 1);
          assertTrue(l.size() == 1);
          q.drainTo(l, 1);
          assertTrue(l.size() == 2);
          assertTrue(l.contains(one));
          assertTrue(l.contains(two));
          t1.join();
          t2.join();
      }
  
  }
  