Changing the return type of a method based on the type of objects in the list

Question

I want to refactor my code from non-typed objects to typed objects.

For example, here is my current code:

public class TestClass {

    ArrayList list = new ArrayList();

    public ArrayList testMethodA() {
        list.add("string1");
        list.add("string2");
        list.add("string3");
        list.add("string4");
        list.add("string5");
        return list;
    }
}

I want to turn this into a typed List, so it becomes

public class TestClass {

    List<String> list = new ArrayList<>();

    public ArrayList<String> testMethodA() {
        list.add("string1");
        list.add("string2");
        list.add("string3");
        list.add("string4");
        list.add("string5");
        return list;
    }
}

Is there a way to change the return type from ArrayList to ArrayList<Object> based on the type of obj1, obj2, ...]? For example, if what's being added to the list are of type String, then is it possible to change the return value from ArrayList to ArrayList<String> dynamically?

I'm using Eclipse, so if there is a plugin (or script or something) that can help me do this it would be much appreciated.

If there is no 'automatic' way of doing this it would mean 5-6 days of manual fixing, which I would rather avoid.

Answer 1

In the java editor: Right-click > Refactor > Infer Generic Type Arguments...

Have a look at the documentation of Eclipse's "Infer Generic Type Arguments" refactoring: http://help.eclipse.org/kepler/index.jsp?topic=/org.eclipse.jdt.doc.user/reference/ref-menu-refactor.htm

Also see this previous stackoverflow question: How to use "Infer Generic Type Arguments..." in Eclipse