Are there any alternatives to implementing Clone in Java?

Question

In my Java project, I have a vector of various types of Traders. These different types of traders are subclasses of the Trader class. Right now, I have a method that takes a

Answer 1

I am a little unclear as to why you would want to store 50 or so clones of the same object unless they the original trader serves as a prototype (see pattern) for later traders.

If you want to make an exact copy of an object, you have to take into account the issue of polymorphism. If people subclassing your given class are allowed to add state members, then you already have enough of a headache with functions like equals and compareTo, that clone is jut one more case where you need to require special handling.

I disagree that clone is always evil, it is sometimes necessary. However, in situations of subclassing, a lot of things become tricky.

I would recommend you read (when you get a chance) Bloch's "Effective Java", which covers a lot of his topics. Bracha's view is that it is not a good idea to let others extend your classes, and that if you do, you need to document very well what they would have to do and hope that they follow your instructions. There really isn't a way to bypass that. You may also want to make your Traders immutable.

Go ahead an implement Clone normally, and indicate very clearly in the class header that anybody inheriting from your Trader and adding state members must implement X methods (specify which).

Finding tricks to bypass an actual Cloneable and still Clone isn't going to overcome the problem of inheritance. There is no silver bullet here.