Operation Enum

public enum Operation {
    PLUS {
        double eval(double x, double y) { return x + y; }
    },
    MINUS {
        double eval(double x, double y) { return x - y; }
    },
    TIMES {
        double eval(double x, double y) { return x \* y; }
    },
    DIVIDED_BY {
        double eval(double x, double y) { return x / y; }
    };

    // Perform the arithmetic operation represented by this constant
    abstract double eval(double x, double y);
    public static void main(String args[]) {
       double x = 2.0;
       double y = 4.0;
       for (Operation op : Operation.values())
           System.out.println(x + " " + op + " " + y + " = " + op.eval(x, y));
      }
}