ThreadLifeCycle
After starting a thread we are not allowed to restart the same thread once again, violation leads to Runtime Error saying “IllegalThreadStateException“.

TestThread t = new TestThread();
t.start();
t.start(); //IllegalThreadStateException

Note: we can’t stop a running Thread explicitly. But until 1.2 version we can achieve this by using stop() method but it is deprecated method. Similarly suspend() and resume() methods also deprecated.