Java Thread : join() example

join() method of the Thread class can be used to join the execution of the currently running thread at end of the execution of some other thread. if you call the join() method on any thread object, the currently running thread will go to sleep (or hold) until that thread object complete its execution. once the its execution is completed, the sleeping/hold thread will resume its execution.

In order to understand the functionality of the join() method clearly, please look at the below sample program.

 

The main method (main thread) of the Application class has created an instance of ThreadA and started it.  as soon as it is started, the main thread has invoked join() method on it.  please check the below code segment of the line number 13.

threadA.join();

Once it is called, the currently running thread ( that is the main thread) will hold its execution and wait until threadA completes its execution.  After threadA going to the dead state, the main thread will be resumed.

if you run the above program, you will get the following output and you can examine the output with the above code.

Main thread started 
ThreadA is running
ThreadA sleeps for 5 seconds
ThreadA was started
Main thread is waiting until ThreadA completes
ThreadA completed
Main thread resumed again after completing ThreadA
Main thread completed

 

One thought on “Java Thread : join() example

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s