Running threads in sequence

Question

Suppose I have the following class below, how can I force the three threads to be executed in order, one after the other successively? (waiting for each other to be terminated)

public class MyRunnable implements Runnable{

    @Override
    public void run() {

        System.out.println("Thread 1 :First Thread started");
    }

    public static Runnable delay(){
        Runnable r = new Runnable(){

            @Override
            public void run() {  // running state

                System.out.println("Thread 2: loading second thread..");
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread 2: System loaded");
            }

        }; // finished state
        return r;
    }

    public static Runnable waiting(){
        Runnable r = new Runnable(){

            @Override
            public void run() { // running state

                System.out.println("Thread 3: waiting..");
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread 3: OK");

            }

        }; // finished state
        return r;
    }


    public static void main(String[] args) throws InterruptedException{

       Thread thread1 = new Thread(new MyRunnable());      
       Thread thread2 = new Thread(delay()); 
       Thread thread3 = new Thread(waiting()); // (initial state)

       thread1.start();
       thread2.start();
       thread3.start();

    }


}

Answer 1

Yes there are, but why do you want to do it?

public static void main(String[] args) throws InterruptedException{

    Thread thread1 = new Thread(new MyRunnable());      
    Thread thread2 = new Thread(delay()); 
    Thread thread3 = new Thread(waiting()); // (initial state)

    thread1.start();
    thread1.join();
    thread2.start();
    thread2.join();
    thread3.start();
    thread3.join();
}

Other way (without threads):

public static void main(String[] args) throws InterruptedException{

    new MyRunnable().run();
    delay().run(); 
    waiting().run();
} 

Your code do this:

Main thread      thread-1        thread-2       thread-3
    V
    |
    + . . . . . . > V
    + . . . . . . . | . . . . . . > V
    + . . . . . . . | . . . . . . . | . . . . . . > V
    X               |               |               |
                    X               |               |
                                    |               |
                                    X               |
                                                    |
                                                    X    

You asked for this (it no make sense because threads can parallelize tasks, and you don't want to parallelize them!):

Main thread      thread-1        thread-2       thread-3
    V
    |
    + . . . . . . > V
    |               |
    |<--------------X
    + . . . . . . . . . . . . . . > V
    |                               |
    |                               |
    |                               |
    |                               |
    |<------------------------------X
    + . . . . . . . . . . . . . . . . . . . . . . > V
    |                                               |
    |                                               |
    |                                               |
    |                                               |
    |                                               |
    |                                               |
    |<----------------------------------------------X
    X

Answer 2

Put thread.join ()after you start the thread. This will wait for the thread to return before the next thread starts.