Java - Extracting code to a generic method when method names are different

Question

I have a code that iterates on some objects of type MyType:

// result is of type Map<Long, MyType>
for (final Map.Entry<Long, MyType> someMyTypeObject: result.entrySet() {
   // Do a bunch of stuff

   Status status = someMyTypeObject.getStatus();

   // Do some more stuff
}

No I'm adding a flow that handles result of type Map<Long, MyNewType> that needs to do exactly the same thing while the only difference is that the method that returns the status is named differently (let's say - getObjectStatus() instead of getStatus()). I can't change either method's name.

I wanted to do something like this:

public <T> doIterationWork(Map<Long, T> result) {
   // Do a bunch of stuff

   Status status = someMyTypeObject.getStatus();

   // Do some more stuff
}

The problem is - I can't use this method because I can't tell which type is T. I thought about overloading 3 methods:

public void getStatus(MyType obj) { return obj.getStatus(); }

public void getStatus(MyNewType obj) { return obj.getObjectStatus(); }

public void getStatus(Object obj) { // throw exception }

But I can't do it because the call is set according to the static type and not the dynamic type (thus I will always get to the Object overload).

Is there a good pattern to handle such case without changing the original classes which is not an option right now?

Answer 1

It's not really elegant, but you could check the type with instanceof, cast the object and call the corresponding method.

Something like this:

Status status;

if (someMyTypeObject instanceof MyType) { // It's a MyType object

    MyType myTypeObject = (MyType) someMyTypeObject;
    status = myTypeObject.getStatus();

} else { // It's a MyNewType object

    MyNewType myNewTypeObject = (MyNewType) someMyTypeObject;
    status = myNewTypeObject.getObjectStatus();

}

Answer 2

You don't know T inside doIterationWork(), but you should known it somewhere upstream, right? If so, you can define a strategy at that point and pass it to doIterationWork():

public <T> doIterationWork(Map<Long, T> result, StatusExtractor<T> statusExtractor) {
    ...
     Status status = statusExtractor.extractStatus(result.getValue());
    ...    
}