I have an array of blasts and an array of zombies, how can I efficiently detect collisions?

Question

I have an array of blasts, and an array of zombies, but I'm struggling to find a way to efficiently detect collisions and remove both the blasts and zombies that have collided. Any suggestions?

    Iterator<Rectangle> blastIter = blasts.iterator();

    while(blastIter.hasNext()) {
        Rectangle blast = blastIter.next();
        blast.x += 200 * Gdx.graphics.getDeltaTime();
        if(blast.x + 16 > 800) blastIter.remove();
    }

    Iterator<Rectangle> zombieIter = zombies.iterator();

    while(zombieIter.hasNext()) {
        Rectangle zombie = zombieIter.next();
        zombie.x -= 150 * Gdx.graphics.getDeltaTime();
        //if(zombie.overlaps(blast)) zombieIter.remove();
    }

Answer 1

You need to put the other iterator inside of the other iterator, try this:

Iterator<Rectangle> zombieIter = zombies.iterator();

while(zombieIter.hasNext()) {

    Rectangle zombie = zombieIter.next();
    zombie.x -= 150 * Gdx.graphics.getDeltaTime();

    Iterator<Rectangle> blastIter = blasts.iterator();

    while(blastIter.hasNext()) {

        Rectangle blast = blastIter.next();
        blast.x += 200 * Gdx.graphics.getDeltaTime();

        if(blast.x + 16 > 800) blastIter.remove();
        if(zombie.overlaps(blast)) zombieIter.remove();

    } 
}