memory leaks - java.lang.OutOfMemoryError: unable to create new native thread

Question

i saw comment like this

one place i have seen this problem is if you keep creating threads, and instead of calling start(), call run() directly on the thread object. This will result in the thread object not getting dereferenced... So after sometime the message unable to create new native thread comes up

on the Sun Java Forums

In my application, initialy we plan to use thread, but later, we decided no need anymore, so we just call run() instead of start(). Do we need to do manual GC for new threadClass(..) ?

my tomcat startup setting

-Xms1024m -Xmx1024m -XX:MaxPermSize=450m 

Answer 1

Why do you create a Thread in the first place?

Your code should implement the Runnable interface instead.

Then, when you decide that you want to run it in a thread, simple instantiate a Thread with the Runnable as the argument and call start() on the Thread object.

If, instead, you just want to run it in your current thread, simply call run() on your Runnable object.

This has several advantages:

• you don't involve any Thread objects as long as you don't care about separate threads
• your code is wrapped in a Runnable which fits closer conceptually: you're not writing some special kind of Thread, do you? You simply write some code that can be executed/run.
• you can easily switch to using an Executor which further abstract away the decision

And last but not least you avoid any potential confusion on whether or not a native thread resource is created.