CODEWITHSUNDEEP
javamultithreadingrace-condition
fscore
fscore

Reputation: 2619

Where is the 2nd thread in the race condition?

The following example is from a book explaining Race conditions. The example says that it has 2 threads. I can only see 1 thread implemented i.e. Thread lo = new Race0();. Can someone please help me understand the program? I am new to multi-threading environment.

Where is the first thread being invoked?

Race0:

class Race0 extends Thread {
    static Shared0 s;
    static volatile boolean done = false;
    public static void main(String[] x) {
        Thread lo = new Race0();
        s = new Shared0();
        try {
            lo.start();
            while (!done) {
                s.bump();
                sleep(30);
            }
            lo.join();
        } catch (InterruptedException e) {
            return;
        }
    }
    public void run() {
        int i;
        try {
            for (i = 0; i < 1000; i++) {
                if (i % 60 == 0)
                    System.out.println();
                System.out.print(“.X”.charAt(s.dif()));
                sleep(20);
            }
            System.out.println();
            done = true;
        } catch (InterruptedException e) {
            return;
        }
    }
}

Shared0:

class Shared0 {
    protected int x = 0, y = 0;
    public int dif() {
        return x - y;
    }
    public void bump() throws InterruptedException {
        x++;
        Thread.sleep(9);
        y++;
    }
}

Upvotes: 2

Views: 95

Answers (1)

Eran
Eran

Reputation: 393946

One thread is the main thread that the main method is running in, and the other thread is the thread that it instantiates and starts (Thread lo = new Race0();).

A java program starts with execuing the main method in the main thread.

This program creates a second thread, lo, starts the thread (by calling lo.start();), and runs a loop.

At this point the main thread is running the loop :

        while (!done) {
            s.bump();
            sleep(30);
        }

At the same time, the second thread, lo, is executing its run method :

    try {
        for (i = 0; i < 1000; i++) {
            if (i % 60 == 0)
                System.out.println();
            System.out.print(“.X”.charAt(s.dif()));
            sleep(20);
        }
        System.out.println();
        done = true;
    } catch (InterruptedException e) {
        return;
    }

Upvotes: 6

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