Limit the number of threads

Hello,
I am developing an application which has to execute untrusted Java source code. The Java security manager is helpful in preventing unauthorized network and local file system access, but as far as I can tell, it can not limit the number of threads created by the untrusted application.
How would I limit the number of threads an untrusted Java application is allowed to create?
Jure
Edited by: zbontarj on Feb 16, 2009 9:46 AM

zbontarj wrote:
Create a custom ThreadGroup will allows only a limited number of threadsI can't see any methods in ThreadGroup that limit the number of threads. There is a method that returns the number of active threads in the group, but that doesn't help me out much.ThreadGroup is not designed for easy extensibility.
You can either take a copy and modify it to take a thread limit. (You can override the default implementation by using -Xbootclasspath/p:path or adding a jar to lib/endorsed however this may contravene the JDK license.)
Or you can write a thread which monitors threads in the thread group every few seconds.
Or you can use the SecurityManager to check the threads in the thread group. The SecurityManager is called each time a thread is added and it can check the threads in the current thread group.

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Is there any way to limit the number of Threads running in Application(JVM)

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You should definitely use a thread pool for this. You can specify maximum number of threads that can be run. Be note that the thread pool will only limit the number of threads that are submitted to it. So donot call "Thread"s start() method to start thread on your own. Submit it to the pool. To know more, study about executor service and thread pool creation. Actually it will not be more than 20 line code for a class and you might need maximum of 2 such classes, one for threadPool and other one for rejection handler (if you want).
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Limit the number of threads

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