public class ThreadCommunication {

    public static void main(String[] args) {

        Business business = new Business();

        new Thread(() -> {

            while (true) {

                try {

                    business.thread1();

                } catch (InterruptedException e) {

                    e.printStackTrace();

                }

            }

        }).start();

        new Thread(() -> {

            while (true) {

                try {

                    business.thread2();

                } catch (InterruptedException e) {

                    e.printStackTrace();

                }

            }

        }).start();

    }

}

class Business {

    private boolean thread1First = true;

    public synchronized void thread1() throws InterruptedException {

        while (!thread1First) {

            this.wait();

        }

        thread1First = !thread1First;

        this.notify();

        System.out.println("thread 1 is called!!!");

        Thread.sleep(1000);

    }

    public synchronized void thread2() throws InterruptedException {

        while (thread1First) {

            this.wait();

        }

        thread1First = !thread1First;

        this.notify();

        System.out.println("thread 2 is invoked");

        Thread.sleep(1000);

    }

}