code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.Collection;
  
  /*
   * Copyright 2005-2006 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 6355660 6347106 6394004
   * @summary methods taking concurrently mutating collection should work
   * @author Martin Buchholz
   */
  
  import java.lang.reflect.*;
  import java.util.*;
  import java.util.concurrent.*;
  
  @SuppressWarnings("unchecked")
  public class HotPotatoes {
      private static void realMain(String[] args) throws Throwable {
          testImplementation(Vector.class);
          testImplementation(ArrayList.class);
          testImplementation(PriorityQueue.class);
          testImplementation(PriorityBlockingQueue.class);
      }
  
      private static void testImplementation(Class<? extends Collection> implClazz)
          throws Throwable
      {
          testPotato(implClazz, Vector.class);
          testPotato(implClazz, CopyOnWriteArrayList.class);
  
          final Constructor<? extends Collection> constr
              = implClazz.getConstructor(Collection.class);
          final Collection<Object> coll
              = constr.newInstance(Arrays.asList(new String[] {}));
          coll.add(1);
          equal(coll.toString(), "[1]");
      }
  
      private static void testPotato(Class<? extends Collection> implClazz,
                                     Class<? extends List> argClazz)
          throws Throwable
      {
          try {
              System.out.printf("implClazz=%s, argClazz=%s\n",
                                implClazz.getName(), argClazz.getName());
              final int iterations = 100000;
              final List<Integer> list = (List<Integer>) argClazz.newInstance();
              final Integer one = Integer.valueOf(1);
              final List<Integer> oneElementList = Collections.singletonList(one);
              final Constructor<? extends Collection> constr
                  = implClazz.getConstructor(Collection.class);
              final Thread t = new CheckedThread() { public void realRun() {
                  for (int i = 0; i < iterations; i++) {
                      list.add(one);
                      list.remove(one);
                  }}};
              t.setDaemon(true);
              t.start();
  
              for (int i = 0; i < iterations; i++) {
                  Collection<?> coll = constr.newInstance(list);
                  Object[] elts = coll.toArray();
                  check(elts.length == 0 ||
                        (elts.length == 1 && elts[0] == one));
              }
          } catch (Throwable t) { unexpected(t); }
      }
  
      //--------------------- 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); }}}
  }
  