Optional Methods in Java Interface

Question

From my understanding if you implement an interface in java, the methods specified in that interface have to be used by the sub classes implementing the said interface.

Answer 1

I was looking for a way to implement the call back interface, so implementing optional methods was necessary since I didn't want to implement every method for each call back.

So, instead of using an interface, I used a class with empty implementation such as:

public class MyCallBack{
    public void didResponseCameBack(String response){}
}

And you can set member variable CallBack like this,

c.setCallBack(new MyCallBack() {
    public void didResponseCameBack(String response) {
        //your implementation here
    }
});

then call it like this.

if(mMyCallBack != null) {
    mMyCallBack.didResponseCameBack(response);
}

This way, you wouldn't need to worry about implementing every methods per call back, but only override the ones you need.