Java interface design: where should I put a lot of duplicate code that will be used by all subclasses?

Question

interface Tuple {
    void method1();
}

class Tuple1 implements Tuple {

    @Override
    public void method1() {
        // some code ....
        utilityMethod();
        // some code ....
    }

    // it will be used by subclasses of Tuple only
    private void utilityMethod(){ 
        // some code....
    }
}

class Tuple2 implements Tuple {

    @Override
    public void method1() {
        // some code ....
        utilityMethod();
        // some code ....
    }

    // it will be used by subclasses of Tuple only
    private void utilityMethod(){
        // some code....
    }
}

the utilityMethod will be used by all subclasses of Tuple, where should I put the utilityMethod best?

From the names, I'm guessing that `Tuple` should actually be an abstract class, rather than an interface. Then all you need to do is declare this method as protected. — Dawood ibn Kareem, Jun 10 '20 at 05:01

score 2 · Answer 1 · answered Jun 10 '20 at 03:08

2

Absent some compelling reasons, I would put it in Tuple. You can make it a default method. Like,

interface Tuple {
    void method1();
    // it will be used by subclasses of Tuple only
    default void utilityMethod(){ 
        // some code....
    }
}

answered Jun 10 '20 at 03:08

Elliott Frisch

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Java interface design: where should I put a lot of duplicate code that will be used by all subclasses?

1 Answers1