使用父类对象创建子类对象？

Question

I want to create an instance of a subclass that contains all the same fields as the parent Object, just with an extra field or two. My plan is this:

public subclass(parentClass parent, String extraField)
{
    super(parent.getField1(), parent.getField2());
    this.extraField = extraField;
}

Is there anything wrong with this design?

Answer 1

That's fine, it's just a copy-constructor-plus.

But ideally, define a copy-constructor on the parent class and use it instead:

public Subclass(ParentClass parent, String extraField) {
    super(parent); // <=== Using the copy constructor
    this.extraField = extraField;
}

(Also, ideally, use Java standard naming conventions, at least when posting code for others to read... ;-) )