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 CopyOnWriteArraySetTest extends JSR166TestCase {
      public static void main(String[] args) {
          junit.textui.TestRunner.run (suite());
      }
      public static Test suite() {
          return new TestSuite(CopyOnWriteArraySetTest.class);
      }
  
      static CopyOnWriteArraySet populatedSet(int n) {
          CopyOnWriteArraySet a = new CopyOnWriteArraySet();
          assertTrue(a.isEmpty());
          for (int i = 0; i < n; ++i)
              a.add(new Integer(i));
          assertFalse(a.isEmpty());
          assertEquals(n, a.size());
          return a;
      }
  
      /**
       * Default-constructed set is empty
       */
      public void testConstructor() {
          CopyOnWriteArraySet a = new CopyOnWriteArraySet();
          assertTrue(a.isEmpty());
      }
  
      /**
       * Collection-constructed set holds all of its elements
       */
      public void testConstructor3() {
          Integer[] ints = new Integer[SIZE];
          for (int i = 0; i < SIZE-1; ++i)
              ints[i] = new Integer(i);
          CopyOnWriteArraySet a = new CopyOnWriteArraySet(Arrays.asList(ints));
          for (int i = 0; i < SIZE; ++i)
              assertTrue(a.contains(ints[i]));
      }
  
  
      /**
       *  addAll adds each element from the given collection
       */
      public void testAddAll() {
          CopyOnWriteArraySet full = populatedSet(3);
          Vector v = new Vector();
          v.add(three);
          v.add(four);
          v.add(five);
          full.addAll(v);
          assertEquals(6, full.size());
      }
  
      /**
       *  addAll adds each element from the given collection that did not
       *  already exist in the set
       */
      public void testAddAll2() {
          CopyOnWriteArraySet full = populatedSet(3);
          Vector v = new Vector();
          v.add(three);
          v.add(four);
          v.add(one); // will not add this element
          full.addAll(v);
          assertEquals(5, full.size());
      }
  
      /**
       *  add will not add the element if it already exists in the set
       */
      public void testAdd2() {
          CopyOnWriteArraySet full = populatedSet(3);
          full.add(one);
          assertEquals(3, full.size());
      }
  
      /**
       *  add  adds the element when it does not exist
       *  in the set
       */
      public void testAdd3() {
          CopyOnWriteArraySet full = populatedSet(3);
          full.add(three);
          assertTrue(full.contains(three));
      }
  
      /**
       *  clear removes all elements from the set
       */
      public void testClear() {
          CopyOnWriteArraySet full = populatedSet(3);
          full.clear();
          assertEquals(0, full.size());
      }
  
      /**
       *   contains returns true for added elements
       */
      public void testContains() {
          CopyOnWriteArraySet full = populatedSet(3);
          assertTrue(full.contains(one));
          assertFalse(full.contains(five));
      }
  
      /**
       * Sets with equal elements are equal
       */
      public void testEquals() {
          CopyOnWriteArraySet a = populatedSet(3);
          CopyOnWriteArraySet b = populatedSet(3);
          assertTrue(a.equals(b));
          assertTrue(b.equals(a));
          assertEquals(a.hashCode(), b.hashCode());
          a.add(m1);
          assertFalse(a.equals(b));
          assertFalse(b.equals(a));
          b.add(m1);
          assertTrue(a.equals(b));
          assertTrue(b.equals(a));
          assertEquals(a.hashCode(), b.hashCode());
      }
  
  
      /**
       *  containsAll returns true for collections with subset of elements
       */
      public void testContainsAll() {
          CopyOnWriteArraySet full = populatedSet(3);
          Vector v = new Vector();
          v.add(one);
          v.add(two);
          assertTrue(full.containsAll(v));
          v.add(six);
          assertFalse(full.containsAll(v));
      }
  
      /**
       *  isEmpty is true when empty, else false
       */
      public void testIsEmpty() {
          CopyOnWriteArraySet empty = new CopyOnWriteArraySet();
          CopyOnWriteArraySet full = populatedSet(3);
          assertTrue(empty.isEmpty());
          assertFalse(full.isEmpty());
      }
  
      /**
       *  iterator() returns an iterator containing the elements of the set
       */
      public void testIterator() {
          CopyOnWriteArraySet full = populatedSet(3);
          Iterator i = full.iterator();
          int j;
          for (j = 0; i.hasNext(); j++)
              assertEquals(j, i.next());
          assertEquals(3, j);
      }
  
      /**
       * iterator remove is unsupported
       */
      public void testIteratorRemove () {
          CopyOnWriteArraySet full = populatedSet(3);
          Iterator it = full.iterator();
          it.next();
          try {
              it.remove();
              shouldThrow();
          } catch (UnsupportedOperationException success) {}
      }
  
      /**
       * toString holds toString of elements
       */
      public void testToString() {
          CopyOnWriteArraySet full = populatedSet(3);
          String s = full.toString();
          for (int i = 0; i < 3; ++i) {
              assertTrue(s.indexOf(String.valueOf(i)) >= 0);
          }
      }
  
  
      /**
       *  removeAll  removes all elements from the given collection
       */
      public void testRemoveAll() {
          CopyOnWriteArraySet full = populatedSet(3);
          Vector v = new Vector();
          v.add(one);
          v.add(two);
          full.removeAll(v);
          assertEquals(1, full.size());
      }
  
  
      /**
       * remove removes an element
       */
      public void testRemove() {
          CopyOnWriteArraySet full = populatedSet(3);
          full.remove(one);
          assertFalse(full.contains(one));
          assertEquals(2, full.size());
      }
  
      /**
       *  size returns the number of elements
       */
      public void testSize() {
          CopyOnWriteArraySet empty = new CopyOnWriteArraySet();
          CopyOnWriteArraySet full = populatedSet(3);
          assertEquals(3, full.size());
          assertEquals(0, empty.size());
      }
  
      /**
       *  toArray returns an Object array containing all elements from the set
       */
      public void testToArray() {
          CopyOnWriteArraySet full = populatedSet(3);
          Object[] o = full.toArray();
          assertEquals(3, o.length);
          assertEquals(0, o[0]);
          assertEquals(1, o[1]);
          assertEquals(2, o[2]);
      }
  
      /**
       *  toArray returns an Integer array containing all elements from
       *  the set
       */
      public void testToArray2() {
          CopyOnWriteArraySet full = populatedSet(3);
          Integer[] i = new Integer[3];
          i = (Integer[])full.toArray(i);
          assertEquals(3, i.length);
          assertEquals(0, (int) i[0]);
          assertEquals(1, (int) i[1]);
          assertEquals(2, (int) i[2]);
      }
  
  
      /**
       *  toArray throws an ArrayStoreException when the given array can
       *  not store the objects inside the set
       */
      public void testToArray_ArrayStoreException() {
          try {
              CopyOnWriteArraySet c = new CopyOnWriteArraySet();
              c.add("zfasdfsdf");
              c.add("asdadasd");
              c.toArray(new Long[5]);
              shouldThrow();
          } catch (ArrayStoreException success) {}
      }
  
      /**
       * A deserialized serialized set is equal
       */
      public void testSerialization() throws Exception {
          CopyOnWriteArraySet q = populatedSet(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));
          CopyOnWriteArraySet r = (CopyOnWriteArraySet)in.readObject();
          assertEquals(q.size(), r.size());
          assertTrue(q.equals(r));
          assertTrue(r.equals(q));
      }
  
  }
  