code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.PriorityQueue;
  
  /*
   * Copyright 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 6394004
   * @summary Test ForgetMeNot implementation feature (and more)
   * @author Martin Buchholz
   */
  
  import java.util.*;
  
  public class ForgetMeNot {
      private static void checkQ(PriorityQueue<Integer> q, Integer...elts) {
          check(Arrays.equals(q.toArray(), elts));
      }
  
      private static void noMoreElements(final Iterator<Integer> it) {
          for (int j = 0; j < 2; j++) {
              THROWS(NoSuchElementException.class,
                     new Fun() { void f() { it.next(); }});
              check(! it.hasNext());
          }
      }
  
      private static void removeIsCurrentlyIllegal(final Iterator<Integer> it) {
          for (int j = 0; j < 2; j++) {
              THROWS(IllegalStateException.class,
                     new Fun() { void f() { it.remove(); }});
          }
      }
  
      private static void remove(Iterator<Integer> it,
                                 Queue<Integer> q) {
          int size = q.size();
          it.remove();
          removeIsCurrentlyIllegal(it);
          equal(size, q.size()+1);
      }
  
      private static void realMain(String[] args) throws Throwable {
          final PriorityQueue<Integer> q = new PriorityQueue<Integer>();
          Iterator<Integer> it;
  
          //----------------------------------------------------------------
          // Empty
          //----------------------------------------------------------------
          checkQ(q);
          check(q.isEmpty());
          check(! q.contains(1));
          it = q.iterator();
          removeIsCurrentlyIllegal(it);
          noMoreElements(it);
          q.clear();
          check(q.isEmpty());
  
          //----------------------------------------------------------------
          // Singleton
          //----------------------------------------------------------------
          q.add(1);
          checkQ(q, 1);
          check(! q.isEmpty());
          check(q.contains(1));
          it = q.iterator();
          removeIsCurrentlyIllegal(it);
          check(it.hasNext());
          equal(it.next(), 1);
          noMoreElements(it);
          remove(it, q);
          check(q.isEmpty());
          noMoreElements(it);
          checkQ(q);
          q.clear();
  
          //----------------------------------------------------------------
          // @see PriorityQueue.forgetMeNot
          //----------------------------------------------------------------
          final Integer[] a = {0, 4, 1, 6, 7, 2, 3}; // Carefully chosen!
          q.addAll(Arrays.asList(a));
          checkQ(q, a);
          it = q.iterator();
          checkQ(q, a);
          removeIsCurrentlyIllegal(it);
          checkQ(q, a);
          check(it.hasNext());
          removeIsCurrentlyIllegal(it);
          checkQ(q, a);
          check(it.hasNext());
          equal(it.next(), 0);
          equal(it.next(), 4);
          equal(it.next(), 1);
          equal(it.next(), 6);
          check(it.hasNext());
          checkQ(q, a);
          remove(it, q);
          checkQ(q, 0, 3, 1, 4, 7, 2);
          check(it.hasNext());
          removeIsCurrentlyIllegal(it);
          equal(it.next(), 7);
          remove(it, q);
          checkQ(q, 0, 2, 1, 4, 3);
          check(it.hasNext());
          removeIsCurrentlyIllegal(it);
          check(it.hasNext());
          equal(it.next(), 3);
          equal(it.next(), 2);
          check(! it.hasNext());
          remove(it, q);
          checkQ(q, 0, 3, 1, 4);
          check(! it.hasNext());
          noMoreElements(it);
          removeIsCurrentlyIllegal(it);
      }
  
      //--------------------- 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 Fun {abstract void f() throws Throwable;}
      static void THROWS(Class<? extends Throwable> k, Fun... fs) {
          for (Fun f : fs)
              try { f.f(); fail("Expected " + k.getName() + " not thrown"); }
              catch (Throwable t) {
                  if (k.isAssignableFrom(t.getClass())) pass();
                  else unexpected(t);}}
  }
  