How to call three threads in Java alternatively

Question

Given the number 1, 2, 3, 4, 5, 6 , 7, 8, 9, 10, 11, 12 I have Three threads, say Thread-1(print 1), Thread-2(print 2) and Thread-3(print 3) and then again hread-1(print 4), Thread-2(print 5) and Thread-3(print 6) and so on.. How I can call them in loop such that they will execute alternatively, Output(Expected)--- 1 2 3 4 5 6 7 8 9 10 11 12 However my below code is only printing 1 2 3

public class RunAlternateThread {

    public static void main(String[] args) throws InterruptedException {
        PrintNum count = new PrintNum();
        Thread t1 = new Thread(new Thread1(count));
        //t1.setPriority(5);
        Thread t2 = new Thread(new Thread2(count));
        //t2.setPriority(7);
        Thread t3 = new Thread(new Thread3(count));
        //t3.setPriority(9);

        t1.start();
        t2.start();
        t3.start();

    }
}

class Thread1 implements Runnable {
    PrintNum count = null;
    Thread1(PrintNum count) {
        this.count = count;
    }

    public void run() {
        synchronized (count) {
                count.print1();
                    //count.wait();
            count.notifyAll();
            try {
                count.wait(2000);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }            }
        }
}

class Thread2 implements Runnable {
    PrintNum count = null;

    Thread2(PrintNum count) {
        this.count = count;
    }

    public void run() {
            synchronized (count) {
                count.print2();
                count.notifyAll();
                try {
                    count.wait(2000);
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
            }
    }
}
class Thread3 implements Runnable {
    PrintNum count = null;

    Thread3(PrintNum count) {
        this.count = count;
    }

    public void run() {
        synchronized (count) {
            count.print3();
            count.notifyAll();
            try {
                count.wait(2000);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        }
    }
}
class PrintNum {
    static int num = 1;
    void print1() {
        if(num == 12) {
            try {
                Thread.sleep(10000);
            }
            catch (Exception e){

            }
        }
        System.out.println(this.num);
        num++;
    }

    void print2() {
        if(num == 12) {
            try {
                Thread.sleep(10000);
            }
            catch (Exception e){

            }
        }
        System.out.println(this.num);
        num++;
    }
    void print3() {
        if(num == 12) {
            try {
                Thread.sleep(10000);
            }
            catch (Exception e){

            }
        }
        System.out.println(this.num);
        num++;
    }
}

Answer 1

This does what you are asking and i left the thread numbers so you can test it

public class Test {
   public static void main(String[] args) {
       PrintNum count = new PrintNum();
       Thread t1 = new MyThread(count, 1);
       Thread t2 = new MyThread(count, 2);
       Thread t3 = new MyThread(count, 3);
       t1.start();
       t2.start();
       t3.start();
   }
}

class MyThread extends Thread implements Runnable {
    final PrintNum count;
    final int threadNum;
    MyThread(PrintNum count, int threadNum) {
        this.count = count;
        this.threadNum = threadNum;
    }
    public void run() {
        while (count.num < 12) {
             synchronized (count) {
                 count.print(this.threadNum);
             }
        }
    }
}
class PrintNum {
    int num = 0;
    void print(int tNum) {
        try {
            this.num++;
            System.out.println(this.num + " Thread: " + tNum);
            this.notifyAll();
            this.wait();
            if(num == 12) this.notifyAll();
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }
}