Return calculated value from enum

Question

please my question are two and very simple

1. misinterpret enum as is

2. this idea missing some important abstraction in my code

code example, where oprt.calc(x, y) isn't compilable, with warning cannot find symbol

public enum Operation {

    PLUS {
        public double calc(double x, double y) {
            return x + y;
        }
    },
    MINUS {
        public double calc(double x, double y) {
            return x - y;
        }
    },
    MULTILPLE {
        public double calc(double x, double y) {
            return x * y;
        }
    },
    DIVIDED_BY {
        public double calc(double x, double y) {
            return x / y;
        }
    };

    public static void main(String args[]) {
        double x = 15.25;
        double y = 24.50;
        for (Operation oprt : Operation.values()) {
            System.out.println(x + " " + oprt + " " 
                    + y + " = " + oprt.calc(x, y));
        }
    }
}

Answer 1

What you miss is abstract declaration of calc() method:

enum Operation {

  PLUS {
      public double calc(double x, double y) {
          return x + y;
      }
  },
  MINUS {
      public double calc(double x, double y) {
          return x - y;
      }
  },
  MULTILPLE {
      public double calc(double x, double y) {
          return x * y;
      }
  },
  DIVIDED_BY {
      public double calc(double x, double y) {
          return x / y;
      }
  };

  **public abstract double calc(double x, double y);**

  public static void main(String args[]) {
      double x = 15.25;
      double y = 24.50;
      for (Operation oprt : Operation.values()) {
          System.out.println(x + " " + oprt + " " 
                  + y + " = " + oprt.calc(x, y));
      }
  }
}