19. Enums are Classes: Constant Specific Logic

Scenario

In Java, enum is much more than a list of constants. Each constant can provide its own implementation of an abstract method.

Code Block

enum Operation {
    PLUS {
        double apply(double x, double y) { return x + y; }
    },
    MINUS {
        double apply(double x, double y) { return x - y; }
    };

    abstract double apply(double x, double y);
}

public class Main {
    public static void main(String[] args) {
        double x = 10, y = 5;
        for (Operation op : Operation.values()) {
            System.out.printf("%f %s %f = %f%n", x, op, y, op.apply(x, y));
        }
    }
}

Take Your Shot

Predicted Output

Type exactly what you think will be printed in the console.