Question

I got the following error when I try to start again my thread.

Exception in thread "Thread-1" java.lang.IllegalThreadStateException
     at java.lang.Thread.start(Unknown Source)
     at com.jrat.server.Server.run(Server.java:159)

Here is the line:

if (!t.isAlive()) t.start();

The code can be executed many times as it is in a loop (socket handler).
As far as I know, this error means that it can’t start a new Thread because it is already running. What’s weird is I have a isAlive before.

Any idea why it is like that?

Thanks.

Answer 1

As far as I know, this error means that it can’t start a new Thread because it is already running.

No, it means you can’t start a thread which has already been started.

You can’t restart a thread, which is what you’re trying to do. From the documentation for start():

Throws: IllegalThreadStateException – if the thread was already started.

You should probably be using an ExecutorService instead, at a guess – but it’s not really clear what you’re trying to do.