Cloning a member Integer...

Question

Hi all experts, if I have a class like MyClass below, I understand from what I've read, that to achieve deep copy, I must clone all members that are not primitives, while the primitives get cloned automatically by Object.clone().
Fine so long, I just make clone methods in the wrapped classes (like MyWrappedClass below) that are called from the top level class' clone. But what about members that are for example String or Integers?? Must I subclass the String and Integer classes to implement their clone method?? Seems lika a long way to go...
Very thankful for any help in resolving this issue/
AC
MyClass implements Cloneable{
int i; //automatically cloned by Object.clone
Integer integer; //How to clone this?
String string; //How to clone this?
MyWrappedClass coolClass;//easy to clone
public Object clone(){
}

Answer 1

I must clone all members that are not
primitives, while the primitives get cloned
automatically by Object.clone().Object.clone() does a byte-level (for lack of a better term) copy of the object's data. That means that it copies all primitives, as you noted, but also copies all pointers. The cloned pointers will point to the same objects as the original object's pointers.
Objects such as Integer or String are immutable, meaning that you give them a value at construction, and cannot change that value. So, if you clone a pointer to an Integer, you have no worries that the value will change unexpectedly.
More complex objects, however, typically have getter and setter methods. For example, a HashMap can have objects added to and removed from it over its lifetime. If you clone an object that contains a HashMap, both the old and new object will point to the same HashMap.
However, the main reason that you use clone() is to make a snapshot of an object, which is then processed differently than the original object. You typically don't want these two streams of execution to see changes made by the other, and the only way to do this is to make a copy of the HashMap (as well as any other contained objects that can be modified).
I will note here, that I can probably count the number of times I've needed clone() on one hand. I would suggest that, before you implement it, you give some thought as to why you need a snapshot of your object, and whether there might not be a better alternative.