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Java Thread Class final void join(long time_in_ms, int time_in_ns) method with Example

Java Thread Class final void join(long time_in_ms, int time_in_ns) method: Here, we are going to learn about the final void join(long time_in_ms, int time_in_ns) method of Thread class with its syntax and example.
Submitted by Preeti Jain, on July 26, 2019

Thread Class final void join(long time_in_ms, int time_in_ns)

• This method is available in package java.lang.Thread.join(long time_in_ms, int time_in_ns).
• join(long time_in_ms, int time_in_ns) method is applicable when currently executing thread wants to wait for a particular amount of time in milliseconds with additional time also in nanoseconds until completing some other thread then we should go for join(long time_in_ms, int time_in_ns) method of Thread class.
• This method is not static so we cannot access this method with the class name too.
• This method is final we can't override this method in child class.
• The return type of this method is void so it does not return anything.
• This method throws an InterruptedException, so it is needed to handle exception either by try-catch or throws otherwise we will get a compile-time error.

For example, We have two threads [t1 – PreparedExamPaper], [t2 – PrintingExamPaper] so will see what will happen.

Let suppose if a thread t1 executes, t2.join(1000, 500) then thread t1 will entered into waiting state for 1000 milliseconds + 500 nanoseconds until t2 completes and suppose in case if t2 couldn't complete its execution in 1000 ms + 500 ns so in that case, t1 will get a chance to execute and if thread t1 goes into waiting state or sleep mode then again t2 will get a chance to execute its execution for 1000 ms + 500 ns and same process will repeat.

Syntax:

    final void join(long time_in_ms, int time_in_ns){
    }

Parameter(s):

When we write t2.join(2000, 1000), so this line means currently executing thread will stop its execution for 2000 milliseconds +1000 nanoseconds until t2 completion.

Return value:

The return type of this method is void, it does not return anything.

Java program to demonstrate example of join(long time_in_ms, int time_in_ns) method

/*  We will use Thread class methods so we are importing 
    the package but it is not mandate because 
    it is imported by default
*/

import java.lang.Thread;

class MyThread extends Thread {
    //Override run() method of Thread class 
    public void run() {

        for (int i = 0; i < 5; ++i) {
            System.out.println("Thread started:" + Thread.currentThread().getName());
            try {
                Thread.sleep(500);
            } catch (Exception ex) {
                System.out.println(ex.getMessage());
            }
        }
        System.out.println("Thread Ended :" + Thread.currentThread().getName());
    }
}

class MainThread1 {
    public static void main(String[] args) throws Exception {

        MyThread mt = new MyThread();
        mt.start();

        /* Note -1*/
        mt.join(1000, 500);

        for (int j = 0; j < 2; ++j)
            System.out.println("Thread started:" + Thread.currentThread().getName());
        System.out.println("Thread ended:" + Thread.currentThread().getName());
    }
}

Note1: Here we have written /*mt.join(1000,500)*/ means currently executing thread [main] will give a chance to another thread named [MyThread mt] for 1000 ms +500 ns and then after main thread will get a chance to execute and if main thread goes into waiting for state or sleep mode then again MyThread will get a chance for 1000 ms +500 ns and this repeats until complete execution of MyThread.

Output

E:\Programs>javac MainThread1.java

E:\Programs>java MainThread1
Thread started:Thread-0
Thread started:Thread-0
Thread started:main
Thread started:main
Thread started:Thread-0
Thread ended:main
Thread started:Thread-0
Thread started:Thread-0
Thread Ended :Thread-0