Stopping native-threads

Question

hi all,
how can i stop native (hanging) threads?
i see that many people have this question but i can't find any real solution.
all the time sun said we should us cancel-flags in a loop in the thread. but how to do this when the threads was written from other with native code (the most original io-classes from sun , eg. java.net.UrlConnection)?!
look at the following code example:
in linux and mac os-x the timeout for dns-lookups needs between 40 and 60 seconds. but what if you don't like to wait so long?! if you like to test many 1000 urls (internal and external urls mixed)
latest with jdk 1.4 you will get almost internel-jvm-error ending in a java-crash if you test in a loop much urls.
but please! if somebody has a thread-save-soluton please post it!
thx
oliver scorp
code-example:
ublic final class Test1 {
private boolean urlErr = false;
private String urlErrMsg = null;
private int urlTimeout = 5;
public final class TestUrlConnection extends Thread{
private String myUrl = null;
public TestUrlConnection(String parMyUrl) {
super();
myUrl = parMyUrl;
public void run(){
try{
if (myUrl == null)
return;
java.net.URL u = new java.net.URL(myUrl);
java.net.URLConnection uc = u.openConnection();
uc.connect(); // 40 sec timout in linux when url not can be connected !!!
// 60 sec timeout in MAC OS-X !!!
// 1 sec timeout in Windows !!! (so, this example maybe doesn't work there!)
}catch(Exception e){
urlErr = true;
urlErrMsg = e.toString();
public Test1() {
super();
public static void main (String args[]) {
Test1 myProg = new Test1();
myProg.myTest1();
public void myTest1() {
try{
String s = "http://www.apache.org";
TestUrlConnection tuc = new TestUrlConnection(s);
tuc.start();
tuc.join(urlTimeout * 1000);
if (tuc.isAlive()){
tuc.stop(); //searching for an alterNATIVE
//is extrem instable in jdk 1.4!
//(get almost internal errors in jvm if you have many 100 test-threads)
//tuc.interrupt(); //doesn't work by native (hanging) threads
//tuc = null; //doesn't stop the thread
urlErr = true;
urlErrMsg = "Connection timeout!";
if (urlErr)
System.out.println(urlErrMsg);
else
System.out.println("Connection ok");
}catch(Exception e){
System.out.println(e.toString());

Answer 1

the question was: how to end native threads - threadsave (without using the 'deprecated' stop-methode)?!So you have a C method (not Java) in which you created a thread that runs C code (not Java) and it is indeed running, not blocked, and you wish to end it?
Seems like a bad design and bad idea to me, because it is very likely that it will cause memory leaks, and since it it hard to cause it to stop at arbritrary points in its execution it will also be hard to use an automated tool to track down those leaks.
But if you have already dealt with all of those issues then you could stop it. The answer to how is specific to the thread library that you are using. So at the very least you would have to specify that. And since this particular topic has nothing to do with java you might find an answer on another list/forum/group faster.
Despite all of the above, if the thread touches java in any way then I would say that trying to stop it arbritrarily is going to be a really bad idea. Java isn't set up for that. And at the very least you will end up with memory leaks (with no way to get rid of them, since they are likely to be internal to the JVM.) And that would be the best outcome. It is also possible that it would make the JVM unstable and I can't imagine any application where that is going to be a good thing.