wait() Method in Java With Examples

// Java program to demonstrate the use of wait() method
class GunFight {
    private int bullets = 40;

    // This method fires the number of bullets that are
    // passed it. When the bullet in magazine becomes zero,
    // it calls the wait() method and releases the lock.
    synchronized public void fire(int bulletsToBeFired)
    {
        for (int i = 1; i <= bulletsToBeFired; i++) {
            if (bullets == 0) {
                System.out.println(i - 1
                                   + " bullets fired and "
                                   + bullets + " remains");
                System.out.println(
                    "Invoking the wait() method");
                try {
                    wait();
                }
                catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(
                    "Continuing the fire after reloading");
            }

            bullets--;
        }
        System.out.println(
            "The firing process is complete");
    }

    // reload() increases the bullets by 40 everytime it is
    // invoked and calls the notify() method which wakes up
    // the thread that was sent to sleep using wait() inside
    // of fire() method
    synchronized public void reload()
    {
        System.out.println(
            "Reloading the magazine and resuming "
            + "the thread using notify()");
        bullets += 40;
        notify();
    }
}

public class WaitDemo extends Thread {
    public static void main(String[] args)
    {

        GunFight gf = new GunFight();

        // Creating a new thread and invoking
        // our fire() method on it
        new Thread() {
            @Override public void run() { gf.fire(60); }
        }.start();

        // Creating a new thread and invoking
        // our reload method on it
        new Thread() {
            @Override public void run() { gf.reload(); }
        }.start();
    }
}