Volatile.java Source code

Introduction

Here is the source code for Volatile.java

Source

public class Volatile extends Object implements Runnable {
    // not marked as 'volatile', but it should be!
    private int value;

    private volatile boolean missedIt;

    // doesn't need to be volatile-doesn't change
    private long creationTime;

    public Volatile() {
        value = 10;
        missedIt = false;
        creationTime = System.currentTimeMillis();
    }

    public void run() {
        print("entering run()");

        // each time, check to see if 'value' is different
        while (value < 20) {
            // Used to break out of the loop if change to
            // value is missed.
            if (missedIt) {
                int currValue = value;

                // Simply execute a synchronized statement on an
                // arbitrary object to see the effect.
                Object lock = new Object();
                synchronized (lock) {
                    // do nothing!
                }

                int valueAfterSync = value;

                print("in run() - see value=" + currValue + ", but rumor has it that it changed!");
                print("in run() - valueAfterSync=" + valueAfterSync);

                break;
            }
        }

        print("leaving run()");
    }

    public void workMethod() throws InterruptedException {
        print("entering workMethod()");

        print("about to sleep for 2 seconds");
        Thread.sleep(2000);

        value = 50;
        print("just set value=" + value);

        print("about to sleep for 5 seconds");
        Thread.sleep(5000);

        missedIt = true;
        print("just set missedIt=" + missedIt);

        print("about to sleep for 3 seconds");
        Thread.sleep(3000);

        print("leaving workMethod()");
    }

    private void print(String msg) {
        long interval = System.currentTimeMillis() - creationTime;

        String tmpStr = (interval / 1000.0) + "000";

        int pos = tmpStr.indexOf(".");
        String secStr = tmpStr.substring(pos - 2, pos + 4);

        String nameStr = Thread.currentThread().getName();

        nameStr = nameStr.substring(nameStr.length() - 8, nameStr.length());

        System.out.println(secStr + " " + nameStr + ": " + msg);
    }

    public static void main(String[] args) {
        try {
            Volatile vol = new Volatile();

            // slight pause to let some time elapse
            Thread.sleep(100);

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

            // slight pause to allow run() to go first
            Thread.sleep(100);

            vol.workMethod();
        } catch (InterruptedException x) {
            System.err.println("one of the sleeps was interrupted");
        }
    }
}