AlternateSuspendResume.java Source code

Introduction

Here is the source code for AlternateSuspendResume.java

Source

public class AlternateSuspendResume extends Object implements Runnable {

    private volatile int firstVal;

    private volatile int secondVal;

    private volatile boolean suspended;

    public boolean areValuesEqual() {
        return (firstVal == secondVal);
    }

    public void run() {
        try {
            suspended = false;
            firstVal = 0;
            secondVal = 0;
            workMethod();
        } catch (InterruptedException x) {
            System.out.println("interrupted in workMethod()");
        }
    }

    private void workMethod() throws InterruptedException {
        int val = 1;

        while (true) {
            // blocks if suspended is true
            waitWhileSuspended();

            stepOne(val);
            stepTwo(val);
            val++;

            // blocks if suspended is true
            waitWhileSuspended();

            Thread.sleep(200); // pause before looping again
        }
    }

    private void stepOne(int newVal) throws InterruptedException {

        firstVal = newVal;
        // simulate some other lengthy process
        Thread.sleep(300);
    }

    private void stepTwo(int newVal) {
        secondVal = newVal;
    }

    public void suspendRequest() {
        suspended = true;
    }

    public void resumeRequest() {
        suspended = false;
    }

    private void waitWhileSuspended() throws InterruptedException {
        while (suspended) {
            Thread.sleep(200);
        }
    }

    public static void main(String[] args) {
        AlternateSuspendResume asr = new AlternateSuspendResume();

        Thread t = new Thread(asr);
        t.start();

        try {
            Thread.sleep(1000);
        } catch (InterruptedException x) {
        }

        for (int i = 0; i < 10; i++) {
            asr.suspendRequest();

            try {
                Thread.sleep(350);
            } catch (InterruptedException x) {
            }

            System.out.println("dsr.areValuesEqual()=" + asr.areValuesEqual());

            asr.resumeRequest();

            try {
                Thread.sleep((long) (Math.random() * 2000.0));
            } catch (InterruptedException x) {
            }
        }
        System.exit(0);
    }
}