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

It is preferable to modify the object this and leave the arguements unchanged.

class ModifiedType {
    public ModifiedType populate(UnmodifiedType arg) {
         return this;
    }
    // or
    public void populate(UnmodifiedType arg) {

    }
}

See StringBuilder as an example.