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 java.io.*;
  
  public class PriorityQueueTest extends JSR166TestCase {
      public static void main(String[] args) {
          junit.textui.TestRunner.run (suite());
      }
      public static Test suite() {
          return new TestSuite(PriorityQueueTest.class);
      }
  
      static class MyReverseComparator implements Comparator {
          public int compare(Object x, Object y) {
              return ((Comparable)y).compareTo(x);
          }
      }
  
      /**
       * Create a queue of given size containing consecutive
       * Integers 0 ... n.
       */
      private PriorityQueue populatedQueue(int n) {
          PriorityQueue q = new PriorityQueue(n);
          assertTrue(q.isEmpty());
          for (int i = n-1; i >= 0; i-=2)
              assertTrue(q.offer(new Integer(i)));
          for (int i = (n & 1); i < n; i+=2)
              assertTrue(q.offer(new Integer(i)));
          assertFalse(q.isEmpty());
          assertEquals(n, q.size());
          return q;
      }
  
      /**
       * A new queue has unbounded capacity
       */
      public void testConstructor1() {
          assertEquals(0, new PriorityQueue(SIZE).size());
      }
  
      /**
       * Constructor throws IAE if capacity argument nonpositive
       */
      public void testConstructor2() {
          try {
              PriorityQueue q = new PriorityQueue(0);
              shouldThrow();
          } catch (IllegalArgumentException success) {}
      }
  
      /**
       * Initializing from null Collection throws NPE
       */
      public void testConstructor3() {
          try {
              PriorityQueue q = new PriorityQueue((Collection)null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * Initializing from Collection of null elements throws NPE
       */
      public void testConstructor4() {
          try {
              Integer[] ints = new Integer[SIZE];
              PriorityQueue q = new PriorityQueue(Arrays.asList(ints));
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * Initializing from Collection with some null elements throws NPE
       */
      public void testConstructor5() {
          try {
              Integer[] ints = new Integer[SIZE];
              for (int i = 0; i < SIZE-1; ++i)
                  ints[i] = new Integer(i);
              PriorityQueue q = new PriorityQueue(Arrays.asList(ints));
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * Queue contains all elements of collection used to initialize
       */
      public void testConstructor6() {
          Integer[] ints = new Integer[SIZE];
          for (int i = 0; i < SIZE; ++i)
              ints[i] = new Integer(i);
          PriorityQueue q = new PriorityQueue(Arrays.asList(ints));
          for (int i = 0; i < SIZE; ++i)
              assertEquals(ints[i], q.poll());
      }
  
      /**
       * The comparator used in constructor is used
       */
      public void testConstructor7() {
          MyReverseComparator cmp = new MyReverseComparator();
          PriorityQueue q = new PriorityQueue(SIZE, cmp);
          assertEquals(cmp, q.comparator());
          Integer[] ints = new Integer[SIZE];
          for (int i = 0; i < SIZE; ++i)
              ints[i] = new Integer(i);
          q.addAll(Arrays.asList(ints));
          for (int i = SIZE-1; i >= 0; --i)
              assertEquals(ints[i], q.poll());
      }
  
      /**
       * isEmpty is true before add, false after
       */
      public void testEmpty() {
          PriorityQueue q = new PriorityQueue(2);
          assertTrue(q.isEmpty());
          q.add(new Integer(1));
          assertFalse(q.isEmpty());
          q.add(new Integer(2));
          q.remove();
          q.remove();
          assertTrue(q.isEmpty());
      }
  
      /**
       * size changes when elements added and removed
       */
      public void testSize() {
          PriorityQueue q = populatedQueue(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(SIZE-i, q.size());
              q.remove();
          }
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.size());
              q.add(new Integer(i));
          }
      }
  
      /**
       * offer(null) throws NPE
       */
      public void testOfferNull() {
          try {
              PriorityQueue q = new PriorityQueue(1);
              q.offer(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * add(null) throws NPE
       */
      public void testAddNull() {
          try {
              PriorityQueue q = new PriorityQueue(1);
              q.add(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * Offer of comparable element succeeds
       */
      public void testOffer() {
          PriorityQueue q = new PriorityQueue(1);
          assertTrue(q.offer(zero));
          assertTrue(q.offer(one));
      }
  
      /**
       * Offer of non-Comparable throws CCE
       */
      public void testOfferNonComparable() {
          try {
              PriorityQueue q = new PriorityQueue(1);
              q.offer(new Object());
              q.offer(new Object());
              q.offer(new Object());
              shouldThrow();
          } catch (ClassCastException success) {}
      }
  
      /**
       * add of comparable succeeds
       */
      public void testAdd() {
          PriorityQueue q = new PriorityQueue(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.size());
              assertTrue(q.add(new Integer(i)));
          }
      }
  
      /**
       * addAll(null) throws NPE
       */
      public void testAddAll1() {
          try {
              PriorityQueue q = new PriorityQueue(1);
              q.addAll(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
      /**
       * addAll of a collection with null elements throws NPE
       */
      public void testAddAll2() {
          try {
              PriorityQueue q = new PriorityQueue(SIZE);
              Integer[] ints = new Integer[SIZE];
              q.addAll(Arrays.asList(ints));
              shouldThrow();
          } catch (NullPointerException success) {}
      }
      /**
       * addAll of a collection with any null elements throws NPE after
       * possibly adding some elements
       */
      public void testAddAll3() {
          try {
              PriorityQueue q = new PriorityQueue(SIZE);
              Integer[] ints = new Integer[SIZE];
              for (int i = 0; i < SIZE-1; ++i)
                  ints[i] = new Integer(i);
              q.addAll(Arrays.asList(ints));
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * Queue contains all elements of successful addAll
       */
      public void testAddAll5() {
          Integer[] empty = new Integer[0];
          Integer[] ints = new Integer[SIZE];
          for (int i = 0; i < SIZE; ++i)
              ints[i] = new Integer(SIZE-1-i);
          PriorityQueue q = new PriorityQueue(SIZE);
          assertFalse(q.addAll(Arrays.asList(empty)));
          assertTrue(q.addAll(Arrays.asList(ints)));
          for (int i = 0; i < SIZE; ++i)
              assertEquals(new Integer(i), q.poll());
      }
  
      /**
       * poll succeeds unless empty
       */
      public void testPoll() {
          PriorityQueue q = populatedQueue(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.poll());
          }
          assertNull(q.poll());
      }
  
      /**
       * peek returns next element, or null if empty
       */
      public void testPeek() {
          PriorityQueue q = populatedQueue(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.peek());
              assertEquals(i, q.poll());
              assertTrue(q.peek() == null ||
                         !q.peek().equals(i));
          }
          assertNull(q.peek());
      }
  
      /**
       * element returns next element, or throws NSEE if empty
       */
      public void testElement() {
          PriorityQueue q = populatedQueue(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.element());
              assertEquals(i, q.poll());
          }
          try {
              q.element();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       * remove removes next element, or throws NSEE if empty
       */
      public void testRemove() {
          PriorityQueue q = populatedQueue(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.remove());
          }
          try {
              q.remove();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       * remove(x) removes x and returns true if present
       */
      public void testRemoveElement() {
          PriorityQueue q = populatedQueue(SIZE);
          for (int i = 1; i < SIZE; i+=2) {
              assertTrue(q.remove(new Integer(i)));
          }
          for (int i = 0; i < SIZE; i+=2) {
              assertTrue(q.remove(new Integer(i)));
              assertFalse(q.remove(new Integer(i+1)));
          }
          assertTrue(q.isEmpty());
      }
  
      /**
       * contains(x) reports true when elements added but not yet removed
       */
      public void testContains() {
          PriorityQueue q = populatedQueue(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertTrue(q.contains(new Integer(i)));
              q.poll();
              assertFalse(q.contains(new Integer(i)));
          }
      }
  
      /**
       * clear removes all elements
       */
      public void testClear() {
          PriorityQueue q = populatedQueue(SIZE);
          q.clear();
          assertTrue(q.isEmpty());
          assertEquals(0, q.size());
          q.add(new Integer(1));
          assertFalse(q.isEmpty());
          q.clear();
          assertTrue(q.isEmpty());
      }
  
      /**
       * containsAll(c) is true when c contains a subset of elements
       */
      public void testContainsAll() {
          PriorityQueue q = populatedQueue(SIZE);
          PriorityQueue p = new PriorityQueue(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertTrue(q.containsAll(p));
              assertFalse(p.containsAll(q));
              p.add(new Integer(i));
          }
          assertTrue(p.containsAll(q));
      }
  
      /**
       * retainAll(c) retains only those elements of c and reports true if changed
       */
      public void testRetainAll() {
          PriorityQueue q = populatedQueue(SIZE);
          PriorityQueue p = populatedQueue(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              boolean changed = q.retainAll(p);
              if (i == 0)
                  assertFalse(changed);
              else
                  assertTrue(changed);
  
              assertTrue(q.containsAll(p));
              assertEquals(SIZE-i, q.size());
              p.remove();
          }
      }
  
      /**
       * removeAll(c) removes only those elements of c and reports true if changed
       */
      public void testRemoveAll() {
          for (int i = 1; i < SIZE; ++i) {
              PriorityQueue q = populatedQueue(SIZE);
              PriorityQueue p = populatedQueue(i);
              assertTrue(q.removeAll(p));
              assertEquals(SIZE-i, q.size());
              for (int j = 0; j < i; ++j) {
                  Integer I = (Integer)(p.remove());
                  assertFalse(q.contains(I));
              }
          }
      }
  
      /**
       * toArray contains all elements
       */
      public void testToArray() {
          PriorityQueue q = populatedQueue(SIZE);
          Object[] o = q.toArray();
          Arrays.sort(o);
          for (int i = 0; i < o.length; i++)
              assertEquals(o[i], q.poll());
      }
  
      /**
       * toArray(a) contains all elements
       */
      public void testToArray2() {
          PriorityQueue q = populatedQueue(SIZE);
          Integer[] ints = new Integer[SIZE];
          ints = (Integer[])q.toArray(ints);
          Arrays.sort(ints);
          for (int i = 0; i < ints.length; i++)
              assertEquals(ints[i], q.poll());
      }
  
      /**
       * iterator iterates through all elements
       */
      public void testIterator() {
          PriorityQueue q = populatedQueue(SIZE);
          int i = 0;
          Iterator it = q.iterator();
          while (it.hasNext()) {
              assertTrue(q.contains(it.next()));
              ++i;
          }
          assertEquals(i, SIZE);
      }
  
      /**
       * iterator.remove removes current element
       */
      public void testIteratorRemove () {
          final PriorityQueue q = new PriorityQueue(3);
          q.add(new Integer(2));
          q.add(new Integer(1));
          q.add(new Integer(3));
  
          Iterator it = q.iterator();
          it.next();
          it.remove();
  
          it = q.iterator();
          assertEquals(it.next(), new Integer(2));
          assertEquals(it.next(), new Integer(3));
          assertFalse(it.hasNext());
      }
  
  
      /**
       * toString contains toStrings of elements
       */
      public void testToString() {
          PriorityQueue q = populatedQueue(SIZE);
          String s = q.toString();
          for (int i = 0; i < SIZE; ++i) {
              assertTrue(s.indexOf(String.valueOf(i)) >= 0);
          }
      }
  
      /**
       * A deserialized serialized queue has same elements
       */
      public void testSerialization() throws Exception {
          PriorityQueue q = populatedQueue(SIZE);
          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));
          PriorityQueue r = (PriorityQueue)in.readObject();
          assertEquals(q.size(), r.size());
          while (!q.isEmpty())
              assertEquals(q.remove(), r.remove());
      }
  }
  