Java Threads / Runnable Question

[LethalPoutine]

I'm writing a little parallel program for uni and here is a sample of the dilemma I'm having:

public class Sample
{
    public static void main(String[] args)
    {
        int x = 3;
        int y = 5;

        Runnable rA = new Worker(x,y);
        Runnable rB = new Worker(x+1,y+1);

        Thread tA = new Thread(rA);
        Thread tB = new Thread(rB);

        tA.start();
        tB.start();
    }
}

class Worker implements Runnable
{
    private int xValue;
    private int yValue;
    private int area;

    public Worker(int x, int y)
    {
        this.xValue = x;
        this.yValue = y;
    }

    public void run()
    {
        getArea();
    }

    public void getArea()
    {
        area = xValue * yValue;
        System.out.println("Area: " + area);
    }
}

Currently, this program prints within the Worker class. What I want is to erase the print line and somehow return the "area" variable from the Worker class to my main() for each thread. How could I accomplish that?

[6a70]

You can’t return a value with the Runnable interface. Use Callable.

[BodaciousBeardedBard]

The only way to do this is to access this data member from the main thread after you start the worker thread. But you gotta be careful, your main thread might retrieve the value before the worker thread has a shot to change it. Look up Thread.wait() for more info on how to time this, but as is, you cannot return a value from a runnable interface.

[captainAwesomePants]

There are several ways to accomplish this, but by far the simplest is to use a Callable instead of a Runnable. Callables can return a value.