CODEWITHSUNDEEP
javainterface
Jickson
Jickson

Reputation: 5193

When to implement interface in class and when to instantiate an anonymous implementation of an interface

When to implement interface in class and when to instantiate an anonymous implementation of an interface. Below are two interfaces. 

public interface InterfaceOne {
    void one();
}

public interface InterfaceTwo {
    void two();
}

Approach 1: Implement interface in class 

public class A implements InterfaceOne, InterfaceTwo {

    private void doSomething() {
        Hello hello = new Hello();
        hello.hi(this);
        hello.bye(this);
    }

    @Override
    public void one() {
        //One
    }

    @Override
    public void two() {
        //Two
    }
}

Approach 2: Instantiate an anonymous implementation of an interface 

public class B {

    private void doSomething() {
        Hello hello = new Hello();
        hello.hi(interfaceOne);
        hello.bye(interfaceTwo);
    }

    private InterfaceOne interfaceOne = new InterfaceOne() {
        @Override
        public void one() {
            //One
        }
    };

    private InterfaceTwo interfaceTwo = new InterfaceTwo() {
        @Override
        public void two() {
            //Two
        }
    };
}

What are the scenarios in which we need to use Approach 1 and Approach 2?

Upvotes: 0

Views: 48

Answers (1)

Jack
Jack

Reputation: 133587

With Java8 things slightly changed because with functional interfaces you are allowed to define lambdas with are internally managed as anonymous classes so the awkward syntax is somewhat saved.

In any case an anonymous class makes sense only when you are dealing with something which doesn't need to be named (think about an ActionListener for a button). A named class instead always makes sense, there is no explicit reason to avoid naming a class.

Upvotes: 1

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