Java return the Object/modify the object (coding guidelines)

Question

If a method populates/modifies an object, would it be preferable to return the object or to keep the return type as void and the method would modify the Object through its r

Answer 1

I would choose the first, as it allows you to choose to either modify the object you pass and return it, or take a copy of the object and return the copy.

public Obj populate(Obj o)
{
    Obj returnObj = o.clone();
    ....
    return returnObj;
}

This allows you to keep a reference to the original object and have reference to the modified object.