Posted in: Thread Pool,ThreadLocal in Java,Threads
A thread can be in one of Four states for threads: new, runnable, blocked, dead.
Step 1: When a thread has just been created using the new operator, it is in the new state.
Step 2: Once start method is invoked (which calls the run method), the thread becomes runnable.
- A runnable thread might not be running.
- There can be many runnable threads. But only one of them can be running at any time point.
- OS decides which thread to run. More on this later.
Step 3: A runnable thread enters the blocked state when
- The thread is currently running and method Thread.sleep is called
- suspend method of the thread is called. (deprecated)
- The thread calls the await method.
- The thread tries to lock an object locked by another thread.
- The thread calls an operation that is blocked on i/o.
Step 4: A blocked reenters runnable state when
- It has slept the specified amount of time.
- resume method of the thread is called. (deprecated)
- Another method calls signal or signalAll
- Object lock released by other thread
- I/O completed.
- Its run method exits. Natural death.
- stop method of the thread is called. (deprecated)
- An exception is thrown but not caught.