Question

I want to execute multiple thread side by side.
ex: There will be a simple counter method, the thread will access the method and will print the counter value. One thread should not wait for another thread to stop before starting.

A sample output [maybe]:

T1 1
T2 1
T1 2
T1 3
T1 4
T2 2
T1 5

I’ve no prior idea on multi-threading and just want to learn.

Answer 1

If the counter is shared you want something like this:

class ThreadTask implements Runnable {
    private static AtomicInteger counter = new AtomicInteger();
    private int id;

    public ThreadTask(int id) { this.id = id; }

    public void run() {
        int local = 0;
        while((local = counter.incrementAndGet()) < 500) {
            System.out.println("T" + id + " " + local);
        }
    }
}

...

new Thread(new ThreadTask(0)).start();
new Thread(new ThreadTask(1)).start();

Otherwise, if you want a per-thread counter:

class ThreadTask implements Runnable {
    private int counter = 0;
    private int id;

    public ThreadTask(int id) { this.id = id; }

    public void run() {
        while(counter < 500) {
            counter++;
            System.out.println("T" + id + " " + counter);
        }
    }
}

...

new Thread(new ThreadTask(0)).start();
new Thread(new ThreadTask(1)).start();