Can a parent thread kill a child thread?

Question

I'm writing a multi-threaded application in which it is possible for one of the threads to go into an infinite loop. Is there any way for a parent thread to actually kill the child thread that has gone into the infinite loop? Of course the parent thread won't actually be able to discern whether or not the child thread is in an infinite loop. I would specify some time out value, and when it has been exceeded, then I would want to kill the child thread. Is this possible without setting any sort of flag that the child would read, because once it gets stuck inside an infinite loop, there will be no way to read the flag.

Answer 1

Here's an example of a program that I wrote to simply ping a server. It works somewhat backwards from what you were looking for (the child interrupts the parent) but should provide some clue:
import java.net.*;
import java.io.*;
import java.util.Date;
public class ServerPing extends Thread {
  String [] args;
  public static void main(String[] args) throws Exception {
    ServerPing sp = new ServerPing(args);
    sp.start();
  ServerPing(String [] args) {
    this.args = args;
  public void run() {
    Pinger pinger = new Pinger(this);
    pinger.start();
    try {
      sleep(30000);
    catch (InterruptedException x) {
      System.exit(0); // this is ok. It means the pinger interrupted.
    System.out.println("TIMEOUT");
    System.exit(1);
class Pinger extends Thread {
  Thread p = null;
  Pinger (Thread p) {
    this.p = p;
  public void run() {
    try {
      URL simpleURL = new URL("http://localhost:7001/ping.jsp");
      BufferedReader in = new BufferedReader(new InputStreamReader(simpleURL.openStream()));
      String inputLine;
      while ((inputLine = in.readLine()) != null)
      System.out.println(inputLine);
      in.close();
      p.interrupt();   // <<-- interrupt the parent
    catch (Exception x) {
      x.printStackTrace();
}