fast rotation calculation between 2 points

public static double angle2d(double cX, double cZ, double pX, double pZ) {
    if (cX == cZ) {
        if (pZ > cZ) {
            return 180;
        }
        else if (pZ < cZ) {
            return 0;
        }
        else {
            throw new RuntimeException("Points were equal");
        }
    }
    else if (pZ == cZ) {
        if (pX > cX) {
            return 90;
        }
        else if (pX < cX) {
            return 270;
        }
        else {
            throw new RuntimeException("Points were equal");
        }
    }
    else {
        double theta = Math.atan2(pX - cX, -(pZ - cZ));
        if (theta < 0.0) {
            theta += 6.2831853071795865d;
        }
        return 57.2957795130823209d * theta;
    }
}