code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.concurrent.CopyOnWriteArraySet;
  
  /*
   * Copyright 2005 Sun Microsystems, Inc.  All Rights Reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
   * CA 95054 USA or visit www.sun.com if you need additional information or
   * have any questions.
   */
  
  /*
   * @test
   * @bug 6330307 6355645
   * @summary Check for race conditions in COWArray classes
   * @author Martin Buchholz
   */
  
  import java.util.*;
  import java.util.concurrent.*;
  
  public class RacingCows {
      private static void realMain(String[] args) throws Throwable {
          final int iterations = 100000;
          final Integer two = Integer.valueOf(2);
          final Integer three = Integer.valueOf(3);
  
          //------------ CopyOnWriteArraySet -------------------------------
          final Set<Integer> s1 = new CopyOnWriteArraySet<Integer>();
          final Set<Integer> s2 = new CopyOnWriteArraySet<Integer>();
          s1.add(1);
  
          final Thread t1 = new CheckedThread() { public void realRun() {
              for (int i = 0; i < iterations; i++) {
                  s2.add(two);
                  s2.remove(two);
              }}};
          t1.start();
  
          for (int i = 0; i < iterations; i++) {
              check(! s1.equals(s2));
              check(! s2.equals(s1));
          }
          t1.join();
  
          //------------ CopyOnWriteArrayList ------------------------------
          final List<Integer> l1 = new CopyOnWriteArrayList<Integer>();
          final List<Integer> l2 = new CopyOnWriteArrayList<Integer>();
          final List<Integer> l3 = new CopyOnWriteArrayList<Integer>();
          l1.add(1);
  
          final Thread t2 = new CheckedThread() { public void realRun() {
              for (int i = 0; i < iterations; i++) {
                  switch (i%2) {
                  case 0: l2.add(two);    break;
                  case 1: l2.add(0, two); break;
                  }
                  switch (i%3) {
                  case 0: l2.remove(two); break;
                  case 1: l2.remove(0);   break;
                  case 2: l2.clear();     break;
                  }}}};
          t2.start();
  
          final Thread t3 = new CheckedThread() { public void realRun() {
              l3.add(three);
              for (int i = 0; i < iterations; i++) {
                  switch (i%2) {
                  case 0: l3.add(two);    break;
                  case 1: l3.add(0, two); break;
                  }
                  switch (i%2) {
                  case 0: l3.remove(two); break;
                  case 1: l3.remove(0);   break;
                  }}}};
          t3.start();
  
          for (int i = 0; i < iterations; i++) {
              check(! l1.equals(l2));
              check(! l2.equals(l1));
  
              // CopyOnWriteArrayList(mutatingCollection)
              try { new CopyOnWriteArrayList<Integer>(l2); }
              catch (Throwable t) { unexpected(t); }
  
              // addAllAbsent(mutatingCollection)
              try { new CopyOnWriteArrayList<Integer>().addAllAbsent(l3); }
              catch (Throwable t) { unexpected(t); }
  
              // addAll(mutatingCollection)
              try { new CopyOnWriteArrayList<Integer>().addAll(l3); }
              catch (Throwable t) { unexpected(t); }
  
              // addAll(int, mutatingCollection)
              try { new CopyOnWriteArrayList<Integer>().addAll(0,l3); }
              catch (Throwable t) { unexpected(t); }
          }
          t2.join();
          t3.join();
      }
  
      //--------------------- Infrastructure ---------------------------
      static volatile int passed = 0, failed = 0;
      static void pass() {passed++;}
      static void fail() {failed++; Thread.dumpStack();}
      static void fail(String msg) {System.out.println(msg); fail();}
      static void unexpected(Throwable t) {failed++; t.printStackTrace();}
      static void check(boolean cond) {if (cond) pass(); else fail();}
      static void equal(Object x, Object y) {
          if (x == null ? y == null : x.equals(y)) pass();
          else fail(x + " not equal to " + y);}
      public static void main(String[] args) throws Throwable {
          try {realMain(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");}
      private static abstract class CheckedThread extends Thread {
          public abstract void realRun() throws Throwable;
          public void run() {
              try { realRun(); } catch (Throwable t) { unexpected(t); }}}
  }
  