code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.AbstractCollection;
  
  /*
   * Copyright 2001-2005 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 4486049 6282555 6318622
   * @summary toString method fails if size changes in between a call to size
   *           and an attempt to iterate.
   * @author Josh Bloch, Martin Buchholz
   */
  
  import java.util.*;
  import java.util.concurrent.*;
  
  public class ToString {
      private static void realMain(String[] args) {
          testCollection(new LinkedHashSet<Object>() {
                  public int size() {
                      return super.size() + 1; // Lies, lies, all lies!
                  }});
          testCollection(new ArrayList<Object>());
          testCollection(new Vector<Object>());
          testCollection(new CopyOnWriteArrayList<Object>());
          testCollection(new CopyOnWriteArraySet<Object>());
      }
  
      private static void testCollection(Collection<Object> c) {
          System.out.println(c.getClass());
          equal(c.toString(), "[]");
          check(c.add("x"));
          equal(c.toString(), "[x]");
          check(c.add("y"));
          equal(c.toString(), "[x, y]");
          check(c.add(null));
          equal(c.toString(), "[x, y, null]");
          if (c instanceof AbstractCollection) {
              check(c.add(c));
              equal(c.toString(), "[x, y, null, (this Collection)]");
          }
      }
  
      //--------------------- 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 {System.out.println(x + " not equal to " + y); fail(); }}
  
      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 Exception("Some tests failed");
      }
  }
  