Thread Life Cycle in Java

In Java, a thread goes through several states during its lifetime, known as the Thread Life Cycle. Understanding the thread life cycle is important for writing multithreaded applications that operate correctly and efficiently.

The thread life cycle in Java has five states:

1. Born/New state: A thread is in the new state when an instance of the Thread class is created, but the start() method has not yet been called. The thread is not yet executing and has not been assigned to a processor.

2. Runnable state: When the start() method is called, the thread enters the runnable state. In this state, the thread is ready to run and is waiting for a processor to be assigned to it.

3. Running state: When a processor is assigned to the thread, it enters the running state. In this state, the thread is executing its code.

4. Waiting state: A thread enters the waiting state when it is waiting for another thread to perform a certain action, such as releasing a lock or notifying it. A thread can also enter the waiting state when it calls methods such as wait(), join(), or sleep().

Similar to the waiting state, a thread enters the timed waiting state when it is waiting for a certain amount of time or waiting for a specific action to occur. This state is entered when a thread calls methods such as wait(timeout), join(timeout), or sleep(timeout).

5. Dead/Terminated state: A thread enters the terminated state when its code has finished executing or when an exception is thrown and not caught. A terminated thread cannot be restarted.

Here is an example that demonstrates the thread life cycle in Java:

                
    public class MyThread implements Runnable {
        public void run() {
            // thread code goes here
        }

        public static void main(String[] args) {
            // create a new thread
            Thread t = new Thread(new MyThread());

            // start the thread
            t.start();

            // wait for the thread to finish
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

In this example, we create a new thread using the Thread class and the Runnable interface. We then start the thread by calling its start() method. The thread enters the runnable state and is waiting for a processor to be assigned to it. When a processor is available, the thread enters the running state and begins executing its code.

The main thread waits for the newly created thread to finish by calling its join() method. This puts the main thread into the waiting state until the new thread finishes executing. When the new thread finishes executing, it enters the terminated state and cannot be restarted.

Overall, understanding the thread life cycle is important for writing efficient and correct multithreaded applications. By understanding the different states a thread can be in, developers can better design and manage their threads to avoid bugs and improve performance.

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