private static int rotation = 0;

public void act() {
    ...
    rotation = getRotation();
    ...
}

public static int getActorsRotation() {
    return rotation;
}

//In the class where you need the rotation of "ball";
//you first need to import java.util.List;
//also you need a integer in your "ball" class to check which ball you want to get the rotation;

private int ballsRotation = 0;

private ball b;

public void act() {
    if (b == null) {
        List<ball> list = getWorld().getObjects(ball.class);
        for (int i = 0; i < list.size(); i++) {
            if (list.get(i).getTheIntegerValue() == 1) { //or any other value. You just must be sure that this ball is the right one.
                b = list.get(i);
            }
        }
    }
    else {
        //the code in which you need the rotation of ball.
    }
}