import java.util.Iterator;
import java.util.Random;
import java.util.Vector;

public class VectorThrasher extends Thread {
    private static Random _random = new Random();
    private static final int VECTOR_FILL_LENGTH = 25;

    public static void say( String msg ) {
	if (false) {
	System.out.println( "VectorThrahser: " + Thread.currentThread().getName() + ": " 
	    + msg );
	}
    }

    public void run() {
	int theKeyToMadness = 10;
	Vector v = null;
	while (true) {
	    if (v == null) {
		v = new Vector();
	    }

	    if (v.size() != 0) {
		// remove everything from the vector. get a monitor on ourselves for the
		// hell of it.
		synchronized (this) {	
		    say( "Clearing out my vector" );
		    for (Iterator i = v.iterator(); i.hasNext();) { 
			i.next();
			i.remove();
		    }
		}
	    } else {
		synchronized (this) {
		    say( "Filling up my vector" );
		    for (int i = 0; i < VECTOR_FILL_LENGTH; ++i) {
			v.add( new Integer(_random.nextInt()) );
		    }
		}
	    }

	    // re-assigning the vector is important to reproduce this problem. it will
	    // keep the hash sycn table busy by hopefully adding new heavy locks into the
	    // chain. Without this re-assignment the heavy lock chains will remain in a
	    // steady state.
	    if (--theKeyToMadness == 0) {
		v = null;
		theKeyToMadness = 10;
	    }
	}
    }
}