高階関数とインターフェイス

Adder.java

class Adder implements Applyable {
    @override
    public int func(int a, int b) {
        return a + b;
    }
}

Applyable.java

interface Applyable {
    public abstract int func(int a, int b);
}

Multiplier.java

class Multiplier implements Applyable {
    @override
    public int func(int a, int b) {
        return a * b;
    }
}

Program.java

class Program {
    public static void main(string[] args) {
        Applyable adder = new Adder();
        System.out.println(apply_2_3(adder));       //=> 5
        
        Applyable multiplier = new Multiplier();
        System.out.println(apply_2_3(multiplier));  //=> 6
    }
    
    private static int apply_2_3(Applyable ap) {
        return ap.func(2, 3);
    }
}