method doesn't finish running - works infinitly

Question

I tried to write simple program and stuck at some point into while loop.

From current output I see that it only print the same data.

But it should be executed at every iteration.

Snippet of code:

public void fight(Droid first, Droid second) {

        while (first.isAlive() & second.isAlive()) {

            if ((random.nextInt(10) + 1) % 2 == 0) {
                shoot(first, second);
            } else {
                shoot(second, first);
            }

            // testing output
            System.out.printf("Droid %s has %d power level%n", first.getName(), first.getPower());
            System.out.printf("Droid %s has %d power level%n", second.getName(), second.getPower());
        }

        if (first.getPower() <= 0) {
            fightResult(second);
        } else {
            fightResult(first);
        }
    }

And here is output:

Droid John has 5 power level
Droid Dik has 8 power level
Droid John has 5 power level
Droid Dik has 8 power level
Droid John has 5 power level
Droid Dik has 8 power level
Droid John has 5 power level
Droid Dik has 8 power level

I made some silly mistake and couldn't find one.

Update:

here is shoot():

private void shoot(Droid first, Droid second) {
    second.setPower(first.getImpact());
}

and Droid class:

public abstract class Droid {

    protected Random random;
    private String name;
    private int power;
    private int impact;

    public Droid(int aPower, int anImpact) {
        power = aPower;
        impact = anImpact;
    }

    public String getName() {
        return name;
    }

    public void setPower(int aPower) {
        power = aPower;
    }

    public void setImpact(int anImpact) {
        impact = anImpact;
    }

    public int getPower() {
        return power;
    }

    public int getImpact() {
        return impact;
    }

    public abstract void fight(Droid first, Droid second);

    public boolean isAlive() {
        boolean result = false;
        if (this.getPower() > 0) result = true;
        return result;
    }
}

• How to solve this trouble?

Answer 1

Your shoot method is incorrect, it keeps setting the droids to each other's impact value.

I suspect you'd want to subtract the impact from the droid's power instead.

Something along the lines of

private void shoot(Droid first, Droid second) {
    second.setPower(second.getPower() - first.getImpact());
}

or somewhat more OO-style:

first.shoot(second);

public void shoot(Droid second) {
    second.absorbImpact(getImpact());
}

public void absorbImpact(int impact) {
    power -= impact;
}

Answer 2

try

private void shoot(Droid first, Droid second) {
    second.setPower(second.getPower() - first.getImpact());
}

Answer 3

You have to call setAlive(false) for one of the Droids to end the infinite loop... While shooting you set the power of the second Droid to the impact of the first one. But you never lower the impact of the Droids...

Answer 4

You seem to be using & (bitwise operator) instead of && (boolean and)

Answer 5

Change this:

while (first.isAlive() & second.isAlive())

to this

while (first.isAlive() && second.isAlive())