The first thing you should know about Cloneable is – don’t use it.
It is very hard to implement cloning with Cloneable right, and the effort is not worth it.
Instead of that use some other options, like apache-commons SerializationUtils (deep-clone) or BeanUtils (shallow-clone), or simply use a copy-constructor.
See here for the views of Josh Bloch about cloning with Cloneable, which explains the many drawbacks of the approach. (Joshua Bloch was a Sun employee, and led the development of numerous Java features.)