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
   */
  
  import junit.framework.*;
  import java.util.*;
  import java.util.concurrent.*;
  
  public class ArrayDequeTest extends JSR166TestCase {
      public static void main(String[] args) {
          junit.textui.TestRunner.run (suite());
      }
  
      public static Test suite() {
          return new TestSuite(ArrayDequeTest.class);
      }
  
      /**
       * Create a queue of given size containing consecutive
       * Integers 0 ... n.
       */
      private ArrayDeque populatedDeque(int n) {
          ArrayDeque q = new ArrayDeque();
          assertTrue(q.isEmpty());
          for (int i = 0; i < n; ++i)
              assertTrue(q.offerLast(new Integer(i)));
          assertFalse(q.isEmpty());
          assertEquals(n, q.size());
          return q;
      }
  
      /**
       * new queue is empty
       */
      public void testConstructor1() {
          assertEquals(0, new ArrayDeque().size());
      }
  
      /**
       * Initializing from null Collection throws NPE
       */
      public void testConstructor3() {
          try {
              ArrayDeque q = new ArrayDeque((Collection)null);
              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);
          ArrayDeque q = new ArrayDeque(Arrays.asList(ints));
          for (int i = 0; i < SIZE; ++i)
              assertEquals(ints[i], q.pollFirst());
      }
  
      /**
       * isEmpty is true before add, false after
       */
      public void testEmpty() {
          ArrayDeque q = new ArrayDeque();
          assertTrue(q.isEmpty());
          q.add(new Integer(1));
          assertFalse(q.isEmpty());
          q.add(new Integer(2));
          q.removeFirst();
          q.removeFirst();
          assertTrue(q.isEmpty());
      }
  
      /**
       * size changes when elements added and removed
       */
      public void testSize() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(SIZE-i, q.size());
              q.removeFirst();
          }
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.size());
              q.add(new Integer(i));
          }
      }
  
      /**
       * push(null) throws NPE
       */
      public void testPushNull() {
          try {
              ArrayDeque q = new ArrayDeque(1);
              q.push(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * peekFirst returns element inserted with push
       */
      public void testPush() {
          ArrayDeque q = populatedDeque(3);
          q.pollLast();
          q.push(four);
          assertSame(four, q.peekFirst());
      }
  
      /**
       *  pop removes next element, or throws NSEE if empty
       */
      public void testPop() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.pop());
          }
          try {
              q.pop();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       * offer(null) throws NPE
       */
      public void testOfferFirstNull() {
          try {
              ArrayDeque q = new ArrayDeque();
              q.offerFirst(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * OfferFirst succeeds
       */
      public void testOfferFirst() {
          ArrayDeque q = new ArrayDeque();
          assertTrue(q.offerFirst(new Integer(0)));
          assertTrue(q.offerFirst(new Integer(1)));
      }
  
      /**
       * OfferLast succeeds
       */
      public void testOfferLast() {
          ArrayDeque q = new ArrayDeque();
          assertTrue(q.offerLast(new Integer(0)));
          assertTrue(q.offerLast(new Integer(1)));
      }
  
      /**
       * add succeeds
       */
      public void testAdd() {
          ArrayDeque q = new ArrayDeque();
          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 {
              ArrayDeque q = new ArrayDeque();
              q.addAll(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * Queue contains all elements, in traversal order, 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(i);
          ArrayDeque q = new ArrayDeque();
          assertFalse(q.addAll(Arrays.asList(empty)));
          assertTrue(q.addAll(Arrays.asList(ints)));
          for (int i = 0; i < SIZE; ++i)
              assertEquals(ints[i], q.pollFirst());
      }
  
      /**
       *  pollFirst succeeds unless empty
       */
      public void testPollFirst() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.pollFirst());
          }
          assertNull(q.pollFirst());
      }
  
      /**
       *  pollLast succeeds unless empty
       */
      public void testPollLast() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = SIZE-1; i >= 0; --i) {
              assertEquals(i, q.pollLast());
          }
          assertNull(q.pollLast());
      }
  
      /**
       *  poll succeeds unless empty
       */
      public void testPoll() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.poll());
          }
          assertNull(q.poll());
      }
  
      /**
       *  remove removes next element, or throws NSEE if empty
       */
      public void testRemove() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.remove());
          }
          try {
              q.remove();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       *  peekFirst returns next element, or null if empty
       */
      public void testPeekFirst() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.peekFirst());
              assertEquals(i, q.pollFirst());
              assertTrue(q.peekFirst() == null ||
                         !q.peekFirst().equals(i));
          }
          assertNull(q.peekFirst());
      }
  
      /**
       *  peek returns next element, or null if empty
       */
      public void testPeek() {
          ArrayDeque q = populatedDeque(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());
      }
  
      /**
       *  peekLast returns next element, or null if empty
       */
      public void testPeekLast() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = SIZE-1; i >= 0; --i) {
              assertEquals(i, q.peekLast());
              assertEquals(i, q.pollLast());
              assertTrue(q.peekLast() == null ||
                         !q.peekLast().equals(i));
          }
          assertNull(q.peekLast());
      }
  
      /**
       * getFirst returns next getFirst, or throws NSEE if empty
       */
      public void testFirstElement() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.getFirst());
              assertEquals(i, q.pollFirst());
          }
          try {
              q.getFirst();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       *  getLast returns next element, or throws NSEE if empty
       */
      public void testLastElement() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = SIZE-1; i >= 0; --i) {
              assertEquals(i, q.getLast());
              assertEquals(i, q.pollLast());
          }
          try {
              q.getLast();
              shouldThrow();
          } catch (NoSuchElementException success) {}
          assertNull(q.peekLast());
      }
  
  
      /**
       *  removeFirst removes next element, or throws NSEE if empty
       */
      public void testRemoveFirst() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertEquals(i, q.removeFirst());
          }
          try {
              q.removeFirst();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       * removeFirstOccurrence(x) removes x and returns true if present
       */
      public void testRemoveFirstOccurrence() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 1; i < SIZE; i+=2) {
              assertTrue(q.removeFirstOccurrence(new Integer(i)));
          }
          for (int i = 0; i < SIZE; i+=2) {
              assertTrue(q.removeFirstOccurrence(new Integer(i)));
              assertFalse(q.removeFirstOccurrence(new Integer(i+1)));
          }
          assertTrue(q.isEmpty());
      }
  
      /**
       * removeLastOccurrence(x) removes x and returns true if present
       */
      public void testRemoveLastOccurrence() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 1; i < SIZE; i+=2) {
              assertTrue(q.removeLastOccurrence(new Integer(i)));
          }
          for (int i = 0; i < SIZE; i+=2) {
              assertTrue(q.removeLastOccurrence(new Integer(i)));
              assertFalse(q.removeLastOccurrence(new Integer(i+1)));
          }
          assertTrue(q.isEmpty());
      }
  
      /**
       * contains(x) reports true when elements added but not yet removed
       */
      public void testContains() {
          ArrayDeque q = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              assertTrue(q.contains(new Integer(i)));
              assertEquals(i, q.pollFirst());
              assertFalse(q.contains(new Integer(i)));
          }
      }
  
      /**
       * clear removes all elements
       */
      public void testClear() {
          ArrayDeque q = populatedDeque(SIZE);
          q.clear();
          assertTrue(q.isEmpty());
          assertEquals(0, q.size());
          assertTrue(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() {
          ArrayDeque q = populatedDeque(SIZE);
          ArrayDeque p = new ArrayDeque();
          for (int i = 0; i < SIZE; ++i) {
              assertTrue(q.containsAll(p));
              assertFalse(p.containsAll(q));
              assertTrue(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() {
          ArrayDeque q = populatedDeque(SIZE);
          ArrayDeque p = populatedDeque(SIZE);
          for (int i = 0; i < SIZE; ++i) {
              boolean changed = q.retainAll(p);
              assertEquals(changed, (i > 0));
              assertTrue(q.containsAll(p));
              assertEquals(SIZE-i, q.size());
              p.removeFirst();
          }
      }
  
      /**
       * removeAll(c) removes only those elements of c and reports true if changed
       */
      public void testRemoveAll() {
          for (int i = 1; i < SIZE; ++i) {
              ArrayDeque q = populatedDeque(SIZE);
              ArrayDeque p = populatedDeque(i);
              assertTrue(q.removeAll(p));
              assertEquals(SIZE-i, q.size());
              for (int j = 0; j < i; ++j) {
                  assertFalse(q.contains(p.removeFirst()));
              }
          }
      }
  
      /**
       *  toArray contains all elements
       */
      public void testToArray() {
          ArrayDeque q = populatedDeque(SIZE);
          Object[] o = q.toArray();
          Arrays.sort(o);
          for (int i = 0; i < o.length; i++)
              assertEquals(o[i], q.pollFirst());
      }
  
      /**
       *  toArray(a) contains all elements
       */
      public void testToArray2() {
          ArrayDeque q = populatedDeque(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.pollFirst());
      }
  
      /**
       * toArray(null) throws NPE
       */
      public void testToArray_BadArg() {
          ArrayDeque l = new ArrayDeque();
          l.add(new Object());
          try {
              Object o[] = l.toArray(null);
              shouldThrow();
          } catch (NullPointerException success) {}
      }
  
      /**
       * toArray with incompatable aray type throws CCE
       */
      public void testToArray1_BadArg() {
          ArrayDeque l = new ArrayDeque();
          l.add(new Integer(5));
          try {
              Object o[] = l.toArray(new String[10]);
              shouldThrow();
          } catch (ArrayStoreException success) {}
      }
  
      /**
       *  iterator iterates through all elements
       */
      public void testIterator() {
          ArrayDeque q = populatedDeque(SIZE);
          int i = 0;
          Iterator it = q.iterator();
          while (it.hasNext()) {
              assertTrue(q.contains(it.next()));
              ++i;
          }
          assertEquals(i, SIZE);
      }
  
      /**
       *  iterator ordering is FIFO
       */
      public void testIteratorOrdering() {
          final ArrayDeque q = new ArrayDeque();
          q.add(new Integer(1));
          q.add(new Integer(2));
          q.add(new Integer(3));
          int k = 0;
          for (Iterator it = q.iterator(); it.hasNext();) {
              assertEquals(++k, it.next());
          }
  
          assertEquals(3, k);
      }
  
      /**
       * iterator.remove removes current element
       */
      public void testIteratorRemove () {
          final ArrayDeque q = new ArrayDeque();
          final Random rng = new Random();
          for (int iters = 0; iters < 100; ++iters) {
              int max = rng.nextInt(5) + 2;
              int split = rng.nextInt(max-1) + 1;
              for (int j = 1; j <= max; ++j)
                  q.add(new Integer(j));
              Iterator it = q.iterator();
              for (int j = 1; j <= split; ++j)
                  assertEquals(it.next(), new Integer(j));
              it.remove();
              assertEquals(it.next(), new Integer(split+1));
              for (int j = 1; j <= split; ++j)
                  q.remove(new Integer(j));
              it = q.iterator();
              for (int j = split+1; j <= max; ++j) {
                  assertEquals(it.next(), new Integer(j));
                  it.remove();
              }
              assertFalse(it.hasNext());
              assertTrue(q.isEmpty());
          }
      }
  
      /**
       *  Descending iterator iterates through all elements
       */
      public void testDescendingIterator() {
          ArrayDeque q = populatedDeque(SIZE);
          int i = 0;
          Iterator it = q.descendingIterator();
          while (it.hasNext()) {
              assertTrue(q.contains(it.next()));
              ++i;
          }
          assertEquals(i, SIZE);
          assertFalse(it.hasNext());
          try {
              it.next();
              shouldThrow();
          } catch (NoSuchElementException success) {}
      }
  
      /**
       *  Descending iterator ordering is reverse FIFO
       */
      public void testDescendingIteratorOrdering() {
          final ArrayDeque q = new ArrayDeque();
          for (int iters = 0; iters < 100; ++iters) {
              q.add(new Integer(3));
              q.add(new Integer(2));
              q.add(new Integer(1));
              int k = 0;
              for (Iterator it = q.descendingIterator(); it.hasNext();) {
                  assertEquals(++k, it.next());
              }
  
              assertEquals(3, k);
              q.remove();
              q.remove();
              q.remove();
          }
      }
  
      /**
       * descendingIterator.remove removes current element
       */
      public void testDescendingIteratorRemove () {
          final ArrayDeque q = new ArrayDeque();
          final Random rng = new Random();
          for (int iters = 0; iters < 100; ++iters) {
              int max = rng.nextInt(5) + 2;
              int split = rng.nextInt(max-1) + 1;
              for (int j = max; j >= 1; --j)
                  q.add(new Integer(j));
              Iterator it = q.descendingIterator();
              for (int j = 1; j <= split; ++j)
                  assertEquals(it.next(), new Integer(j));
              it.remove();
              assertEquals(it.next(), new Integer(split+1));
              for (int j = 1; j <= split; ++j)
                  q.remove(new Integer(j));
              it = q.descendingIterator();
              for (int j = split+1; j <= max; ++j) {
                  assertEquals(it.next(), new Integer(j));
                  it.remove();
              }
              assertFalse(it.hasNext());
              assertTrue(q.isEmpty());
          }
      }
  
  
      /**
       * toString contains toStrings of elements
       */
      public void testToString() {
          ArrayDeque q = populatedDeque(SIZE);
          String s = q.toString();
          for (int i = 0; i < SIZE; ++i) {
              assertTrue(s.indexOf(String.valueOf(i)) >= 0);
          }
      }
  
      /**
       * peekFirst returns element inserted with addFirst
       */
      public void testAddFirst() {
          ArrayDeque q = populatedDeque(3);
          q.addFirst(four);
          assertSame(four, q.peekFirst());
      }
  
      /**
       * peekLast returns element inserted with addLast
       */
      public void testAddLast() {
          ArrayDeque q = populatedDeque(3);
          q.addLast(four);
          assertSame(four, q.peekLast());
      }
  
  }
  