问Java中的方法重载有什么问题？

EN

package vl06.math;

public class Mathematik1 {

    public static void main(final String[] args)
    {
        // Fuege hier deine Methoden ein

        /*int sum;
        double summe;

        int a;
        int b;
        int c;

        double d;
        double e;
        double f;*/



        public int addition(int a, int b)
        {
            int sum = 0;
            int sum = a + b;
            return sum;
            System.out.println(sum);
        }

        public int addition(int a, int b, int c)
        {
            int sum = 0;
            int sum = a + b + c;
            return sum;
            System.out.println(sum);
        }

        public double addition(double a, double b)
        {
            double sum = 0.0;
            double sum = a + b;
            return sum;
            System.out.println(sum);
        }

        public double addition(double a, double b, double c)
        {
            double sum = 0.0;
            double sum = a + b + c;
            return sum;
            System.out.println(sum);
        }
    }
}