Java : clone() operation calling super.clone()

java clone
TurtleToes picture TurtleToes · Mar 25, 2011 · Viewed 30.7k times · Source

I am not fully understanding the idea of returning super.clone() in the clone() method of a class. First of all, wouldn't that relate to it returning an object that is a superclass which contains LESS data than requested, because a superclass "is not a" subclass, but a subclass "is a" superclass. And if there were a long chain of subclasses, each calling super.clone(), why wouldn't that lead to it eventually calling Object.clone() at the root of the chain, which isn't any of the subclasses?

Sorry if that was confusing; I confuse myself sometimes

Answer

Laurent Pireyn picture Laurent Pireyn · Mar 25, 2011

The implementation of clone() in Object checks if the actual class implements Cloneable, and creates an instance of that actual class.

So if you want to make your class cloneable, you have to implement Cloneable and downcast the result of super.clone() to your class. Another burden is that the call to super.clone() can throw a CloneNotSupportedException that you have to catch, even though you know it won't happen (since your class implements Cloneable).

The Cloneable interface and the clone method on the Object class are an obvious case of object-oriented design gone wrong.

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