code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.loops;
  
  /*
   * Written by Doug Lea and Josh Bloch with assistance from members of
   * JCP JSR-166 Expert Group and released to the public domain, as
   * explained at http://creativecommons.org/licenses/publicdomain
   */
  import java.util.*;
  
  public class SetBash {
      static Random rnd = new Random();
  
      public static void main(String[] args) {
  	int numItr = Integer.parseInt(args[1]);
  	int setSize = Integer.parseInt(args[2]);
  	Class cl = null;
  
  	try {
  	    cl = Class.forName(args[0]);
  	} catch (ClassNotFoundException e) {
  	    fail("Class " + args[0] + " not found.");
  	}
  
          boolean synch = (args.length>3);
  
  	for (int i=0; i<numItr; i++) {
  	    Set s1 = newSet(cl, synch);
  	    AddRandoms(s1, setSize);
  
  	    Set s2 = newSet(cl, synch);
  	    AddRandoms(s2, setSize);
  
  	    Set intersection = clone(s1, cl, synch);
              intersection.retainAll(s2);
  	    Set diff1 = clone(s1, cl, synch); diff1.removeAll(s2);
  	    Set diff2 = clone(s2, cl, synch); diff2.removeAll(s1);
  	    Set union = clone(s1, cl, synch); union.addAll(s2);
  
  	    if (diff1.removeAll(diff2))
  		fail("Set algebra identity 2 failed");
  	    if (diff1.removeAll(intersection))
  		fail("Set algebra identity 3 failed");
  	    if (diff2.removeAll(diff1))
  		fail("Set algebra identity 4 failed");
  	    if (diff2.removeAll(intersection))
  		fail("Set algebra identity 5 failed");
  	    if (intersection.removeAll(diff1))
  		fail("Set algebra identity 6 failed");
  	    if (intersection.removeAll(diff1))
  		fail("Set algebra identity 7 failed");
  
  	    intersection.addAll(diff1); intersection.addAll(diff2);
  	    if (!intersection.equals(union))
  		fail("Set algebra identity 1 failed");
  
  	    Iterator e = union.iterator();
  	    while (e.hasNext())
  		if (!intersection.remove(e.next()))
  		    fail("Couldn't remove element from copy.");
  	    if (!intersection.isEmpty())
  		fail("Copy nonempty after deleting all elements.");
  
  	    e = union.iterator();
  	    while (e.hasNext()) {
  		Object o = e.next();
  		if (!union.contains(o))
  		    fail("Set doesn't contain one of its elements.");
  		e.remove();
  		if (union.contains(o))
  		    fail("Set contains element after deletion.");
  	    }
  	    if (!union.isEmpty())
  		fail("Set nonempty after deleting all elements.");
  
  	    s1.clear();
  	    if (!s1.isEmpty())
  		fail("Set nonempty after clear.");
  	}
  	System.out.println("Success.");
      }
  
      // Done inefficiently so as to exercise toArray
      static Set clone(Set s, Class cl, boolean synch) {
  	Set clone = newSet(cl, synch);
  	clone.addAll(Arrays.asList(s.toArray()));
  	if (!s.equals(clone))
  	    fail("Set not equal to copy.");
  	if (!s.containsAll(clone))
  	    fail("Set does not contain copy.");
  	if (!clone.containsAll(s))
  	    fail("Copy does not contain set.");
  	return clone;
      }
  
      static Set newSet(Class cl, boolean synch) {
  	try {
  	    Set s = (Set) cl.newInstance();
              if (synch)
                  s = Collections.synchronizedSet(s);
  	    if (!s.isEmpty())
  		fail("New instance non empty.");
  	    return s;
  	} catch (Throwable t) {
  	    fail("Can't instantiate " + cl + ": " + t);
  	}
  	return null; //Shut up compiler.
      }
  
      static void AddRandoms(Set s, int n) {
  	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))
  		fail ("Element not present after addition.");
  	    if (added == prePresent)
  		fail ("added == alreadyPresent");
  	    int postSize = s.size();
  	    if (added && preSize == postSize)
  		fail ("Add returned true, but size didn't change.");
  	    if (!added && preSize != postSize)
  		fail ("Add returned false, but size changed.");
  	}
      }
  
      static void fail(String s) {
  	System.out.println(s);
  	System.exit(1);
      }
  }
  