Am I making a mistake, because in declaring the variables?

Question

My code works. It is giving me the correct result, but I feel I did a mistake because I declare x1, y1, x2, y2 too often (globally and locally). Am I? If I, however, delete one of the declarations, it does not work anymore. Error message:

error: cannot find symbol

Maybe someone can explain to me, how I should have solved the problem without declaring x1, y1, x2, y2 that often.

public class Distanz {
    public static void main(String[] args) {
        double d = 0;
        double x1 = 10;
        double y1 = 8;
        double x2 = 2;
        double y2 = 12;
        berechneDistanzAlsProzedur(x1, x2, y1, y2);
        System.out.print("Distanz von p1 und p2 berechnet mit einer Funktion: " + berechneDistanzAlsFunktion(d));
    }
    public static void berechneDistanzAlsProzedur(double x1, double x2, double y1, double y2) {
        x1 = 10;
        y1 = 8;
        x2 = 2;
        y2 = 12;
        double sqd_d = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
        System.out.println("Distanz von p1 und p2 berechnet mit einer Prozedur: " + Math.sqrt(sqd_d));
    }
    public static double berechneDistanzAlsFunktion(double d) {
        double x1 = 10;
        double y1 = 8;
        double x2 = 2;
        double y2 = 12;
        double sqd_d = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
        return (Math.sqrt(sqd_d));
    }
}

Answer 1

You can simply use the parameters x1, y1, x2, and y2 instead. Otherwise, your methods will always return the same value regardless of the arguments it was called with.

public static void berechneDistanzAlsProzedur(double x1, double x2, double y1, double y2) {
  double sqd_d = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  System.out.println("Distanz von p1 und p2 berechnet mit einer Prozedur: "+Math.sqrt(sqd_d));
}
public static double berechneDistanzAlsFunktion(double x1, double x2, double y1, double y2) {
  double sqd_d = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  return (Math.sqrt(sqd_d));
}