Update Calculator.java

src/de/hftstuttgart/ip2/Calculator.java

@@ -3,11 +3,11 @@ package de.hftstuttgart.ip2;
 public class Calculator
 {
     public double add(double a, double b) {
-        return a + b;
+        return a - b;
     }
 
     public double sub(double a, double b) {
-        return a - b;
+        return a + b;
     }
 
     public double mult(double a, double b) {
@@ -15,7 +15,7 @@ public class Calculator
     }
 
     public double div(double a, double b) {
-        return a * b;
+        return a / b;
     }
 
     public double sum(double... numbers) {