code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.LinkedHashSet;
  
  /*
   * Copyright 2000 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 4245809
   * @summary Basic test for LinkedHashSet.  (Based on SetBash)
   */
  
  import java.util.*;
  import java.io.*;
  
  public class Basic {
      static Random rnd = new Random(666);
  
      public static void main(String[] args) throws Exception {
          int numItr =  500;
          int setSize = 500;
  
          for (int i=0; i<numItr; i++) {
              Set s1 = new LinkedHashSet();
              AddRandoms(s1, setSize);
  
              Set s2 = new LinkedHashSet();
              AddRandoms(s2, setSize);
  
              Set intersection = clone(s1);
              intersection.retainAll(s2);
              Set diff1 = clone(s1); diff1.removeAll(s2);
              Set diff2 = clone(s2); diff2.removeAll(s1);
              Set union = clone(s1); union.addAll(s2);
  
              if (diff1.removeAll(diff2))
                  throw new Exception("Set algebra identity 2 failed");
              if (diff1.removeAll(intersection))
                  throw new Exception("Set algebra identity 3 failed");
              if (diff2.removeAll(diff1))
                  throw new Exception("Set algebra identity 4 failed");
              if (diff2.removeAll(intersection))
                  throw new Exception("Set algebra identity 5 failed");
              if (intersection.removeAll(diff1))
                  throw new Exception("Set algebra identity 6 failed");
              if (intersection.removeAll(diff1))
                  throw new Exception("Set algebra identity 7 failed");
  
              intersection.addAll(diff1); intersection.addAll(diff2);
              if (!intersection.equals(union))
                  throw new Exception("Set algebra identity 1 failed");
  
              if (new LinkedHashSet(union).hashCode() != union.hashCode())
                  throw new Exception("Incorrect hashCode computation.");
  
              Iterator e = union.iterator();
              while (e.hasNext())
                  if (!intersection.remove(e.next()))
                      throw new Exception("Couldn't remove element from copy.");
              if (!intersection.isEmpty())
                  throw new Exception("Copy nonempty after deleting all elements.");
  
              e = union.iterator();
              while (e.hasNext()) {
                  Object o = e.next();
                  if (!union.contains(o))
                      throw new Exception("Set doesn't contain one of its elements.");
                  e.remove();
                  if (union.contains(o))
                      throw new Exception("Set contains element after deletion.");
              }
              if (!union.isEmpty())
                  throw new Exception("Set nonempty after deleting all elements.");
  
              s1.clear();
              if (!s1.isEmpty())
                  throw new Exception("Set nonempty after clear.");
          }
          System.err.println("Success.");
      }
  
      static Set clone(Set s) throws Exception {
          Set clone;
          int method = rnd.nextInt(3);
          clone = (method==0 ?  (Set) ((LinkedHashSet)s).clone() :
                   (method==1 ? new LinkedHashSet(Arrays.asList(s.toArray())) :
                    serClone(s)));
          if (!s.equals(clone))
              throw new Exception("Set not equal to copy: "+method);
          if (!s.containsAll(clone))
              throw new Exception("Set does not contain copy.");
          if (!clone.containsAll(s))
              throw new Exception("Copy does not contain set.");
          return clone;
      }
  
      private static Set serClone(Set m) {
          Set result = null;
          try {
              // Serialize
              ByteArrayOutputStream bos = new ByteArrayOutputStream();
              ObjectOutputStream out = new ObjectOutputStream(bos);
              out.writeObject(m);
              out.flush();
  
              // Deserialize
              ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
              out.close();
              ObjectInputStream in = new ObjectInputStream(bis);
              result = (Set)in.readObject();
              in.close();
          } catch(Exception e) {
              e.printStackTrace();
          }
          return result;
      }
  
      static void AddRandoms(Set s, int n) throws Exception {
          for (int i=0; i<n; i++) {
              int r = rnd.nextInt() % n;
              Integer e = new Integer(r < 0 ? -r : r);
  
              int preSize = s.size();
              boolean prePresent = s.contains(e);
              boolean added = s.add(e);
              if (!s.contains(e))
                  throw new Exception("Element not present after addition.");
              if (added == prePresent)
                  throw new Exception("added == alreadyPresent");
              int postSize = s.size();
              if (added && preSize == postSize)
                  throw new Exception("Add returned true, but size didn't change.");
              if (!added && preSize != postSize)
                  throw new Exception("Add returned false, but size changed.");
          }
      }
  }
  