JAVA EE: Java Tutorial : Java Threads (Life cycle of a Thread in Java

Tuesday, 29 November 2016

Java Tutorial : Java Threads (Life cycle of a Thread in Java | Java thread life cycle_V3)

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Understanding the Life Cycle of a Thread in Java

Every thread in Java follows a specific path from the moment it is initialized until it completes its execution and gets destroyed. Understanding these distinct states helps you manage concurrency effectively and avoid issues like deadlocks and race conditions.

Detailed Stages: From Creation to Destruction

1. Creation (New State)

A thread begins its life cycle in the New state when an instance of the Thread class is instantiated. At this stage, code execution has not started, and the thread is simply an object residing in memory.

2. Runnable and Running

When you call the start() method, the thread moves to the Runnable state. Once the operating system's thread scheduler allocates CPU execution time, the thread transitions into the Running state, executing the logic written inside the run() method.

3. Non-Runnable (Blocked / Waiting / Timed Waiting)

While executing, a thread can temporarily pause its execution due to several conditions:

Blocked: Waiting to acquire a monitor lock held by another thread.
Waiting: Suspended until another thread issues a notification using notify() or notifyAll().
Timed Waiting: Paused for a specified duration using methods such as Thread.sleep(milliseconds).

4. Destruction (Dead / Terminated State)

A thread reaches the Terminated (dead) state once its run() method execution completes naturally or if an uncaught exception halts it. A thread in this state cannot be re-started.