Object cloning question

Question

Hello all,
I have a question about cloning a class. My class is something like this...
public class Message implements Cloneable
  int id;
  Fields fromClient;
  Fields fromProcessor;
  Fields toClient;
  Fields toProcessor;
  protected Object clone() throws CloneNotSupportedException
    return (super.clone());
}FYI, the Fields object is another class that contains a Vector of Field objects... A Field is simple class containing three strings, one string named name, one is named value, the other string is named defaultValue.
At application startup, I create this class and each of the Fields objects are initialized with various Field object stuff.
Message baseMessage = new Message();Later in the process, when I need to create a new Message object, instead of doing a 'new' I instead do a
Message msg1 = baseMessage.clone();The newly cloned msg1 object is then processed and manipulated.
The problem I am having is that on the next call to
Message msg2 = baseMessage.clone();the newly cloned msg2 object contains the contents of msg1! This is very strange because I thought that msg2 would be a clone of baseMessage which does not contain any of the information found in msg1...
Any ideas? I hope I explained it well enough...
Thanks,
-Jeff

Answer 1

Also, did you realy intend your clone() method tobe protected?
I am not really sure why a make the clone()
protected. I most likely read somewhere that it
needed to be protected... Is this a bad thing?Not necessarily. It depends on who you want to be able to clone your object. If you want everbody to be able to, make it public. If you want only classes in that package and subclasses of your class to be able to do it, make it protected. I just wondered because public is probably more common.
As for your other comment about why you weren't using new: You can still use new to make a deep or shallow copy. It's called a copy constructor.
public class Message {
  public Message(Message orig) {
    field1 = orig.field1; // shallow copy
    field2 = new Field2(orig.field2); // deep copy, assuming Field2 has such a constructor
    etc.
}