code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.Collections;
  
  /*
   * Copyright 1999 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 4268780
   * @summary Collection-views of submap-views of synchronized-views of
   *          SortedMap objects do not synchronize on the correct object.
   *          (Got that?)
   */
  
  import java.util.*;
  
  public class ViewSynch {
      static final Integer ZERO = new Integer(0);
      static final Int INT_ZERO = new Int(0);
      static final Int INT_ONE = new Int(1);
      static SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
      static Map m2 = m.tailMap(ZERO);
      static Collection c = m2.values();
  
      public static void main(String[] args) {
          for (int i=0; i<10000; i++)
              m.put(new Integer(i), INT_ZERO);
  
          new Thread() {
              public void run() {
                  for (int i=0; i<100; i++) {
                      Thread.yield();
                      m.remove(ZERO);
                      m.put(ZERO, INT_ZERO);
                  }
              }
          }.start();
  
          c.contains(INT_ONE);
      }
  }
  
  /**
   * Like Integer, except yields while doing equals comparison, to allow
   * for interleaving.
   */
  class Int {
      Integer x;
      Int(int i) {x = new Integer(i);}
  
      public boolean equals(Object o) {
          Thread.yield();
          Int i = (Int)o;
          return x.equals(i.x);
      }
  
      public int hashCode() {return x.hashCode();}
  }
  