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Message:

clone() & toString()

Posted by Ashish Sahni on 02 Oct 1998, 11:50 AM

> > Bill

> > I am a regular reader of your Design Techniques column. It is great. Thank you for all your efforts.

> > My question is that in you Worker.clone() method, why the name attribute is not copied?

> I didn't bother to clone the name variable, because it holds
> a reference to an immutable String object. Since no one can
> change the String object, it doesn't need to be cloned. Both
> Worker clones can share a reference to the same name String.
I have a question regarding the clone method which is not
directly related to the discussion above

A tutorial on the Javasoft site http://java.sun.com/docs/books/tutorial/java/more/objectclass.html
mentions the following

"Be careful: clone should not use new to create the clone and should not call constructors."

I was wondering why. As long as one gets a cloned object how should
it matter whether its created using new or java.lang.Object.clone()

> > Also I think all class should implement toString() method. My reason is very pratical. When you do debug, at any stage, by

> > System.out.println(worker.toString());

> > you can see the states of the instance. I have implemented the method in all my classes. I found it very helpful in my debugging process, expecially in the distributed computing envirronment.

> > Looking forword to hearing your comments.

> This is one I thought about. I wanted to hear what people
> would say about my leaving out overriding toString(). So
> far you are the only person who complained, but on the
> other hand, no one has said, "Rah, rah, rah, it's about time
> someone said you don't need to always override toString()."

> I left it out because in most of the Java classes I have
> written, I didn't override toString(), even though it
> suggests it in the Java specs and javadoc documentation.
> I have only overridden toString() when I was specifically
> needing to look at the output of toString(), usually for
> debugging purposes. That was rare, so I left it out of
> the idiom mostly just based on my own experience.
Bill, u must be very talented programmer to rarely
use debugging but for most of us its a very common thing.
I always see to it that the toString method of an
application specific class reflects the state of the object
by returning the variable/attribute name and their values in
a form that is readable( ofcourse ) AND understandable format.
java.util.Properties prints out the state of a Properties
object in a similar fashion.
If it printed out
@ ....
one would have to enumerate thru all the key/value pairs
and print them out.

I think it good Object Oriented design when the object
state is reflected as explicitly as possible cause
a lot of other folks might be using your code who might
require this feature even if one does not require it.

-Ashish

> So the question is, does anybody else out there have an
> opinion on toString()?

> bv

• toString() Reginald Braithwaite-Lee 08 Oct 1998, 7:22 AM (0)