code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.Collections;
  
  /*
   * Copyright 2007 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 6585904
   * @summary Checked collections with underlying maps with identity comparisons
   */
  
  import java.util.*;
  import static java.util.Collections.*;
  
  public class CheckedIdentityMap {
      void test(String[] args) throws Throwable {
          Map<Integer, Integer> m1 = checkedMap(
              new IdentityHashMap<Integer, Integer>(),
              Integer.class, Integer.class);
          Map<Integer, Integer> m2 = checkedMap(
              new IdentityHashMap<Integer, Integer>(),
              Integer.class, Integer.class);
          m1.put(new Integer(1), new Integer(1));
          m2.put(new Integer(1), new Integer(1));
  
          Map.Entry<Integer, Integer> e1 = m1.entrySet().iterator().next();
          Map.Entry<Integer, Integer> e2 = m2.entrySet().iterator().next();
          check(! e1.equals(e2));
          check(e1.hashCode() == hashCode(e1));
          check(e2.hashCode() == hashCode(e2));
      }
  
      int hashCode(Map.Entry<?,?> e) {
          return (System.identityHashCode(e.getKey()) ^
                  System.identityHashCode(e.getValue()));
      }
  
      //--------------------- Infrastructure ---------------------------
      volatile int passed = 0, failed = 0;
      void pass() {passed++;}
      void fail() {failed++; Thread.dumpStack();}
      void fail(String msg) {System.err.println(msg); fail();}
      void unexpected(Throwable t) {failed++; t.printStackTrace();}
      void check(boolean cond) {if (cond) pass(); else fail();}
      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 {
          new CheckedIdentityMap().instanceMain(args);}
      void instanceMain(String[] args) throws Throwable {
          try {test(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");}
      abstract class F {abstract void f() throws Throwable;}
      void THROWS(Class<? extends Throwable> k, F... fs) {
          for (F f : fs)
              try {f.f(); fail("Expected " + k.getName() + " not thrown");}
              catch (Throwable t) {
                  if (k.isAssignableFrom(t.getClass())) pass();
                  else unexpected(t);}}
      Thread checkedThread(final Runnable r) {
          return new Thread() {public void run() {
              try {r.run();} catch (Throwable t) {unexpected(t);}}};}
  }
  