Re: operator overloading

From:
Tom Anderson <twic@urchin.earth.li>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 22 May 2008 18:50:35 +0100
Message-ID:
<Pine.LNX.4.64.0805221848410.10241@urchin.earth.li>
On Wed, 21 May 2008, Mark Space wrote:

Tom Anderson wrote:

Hmm. What happens if i call get(int) on my three-dimensional matrix?


A slightly more practical implementation would be something like:

 public abstract class AbstractMatrix<class T>
 {
   public T get( int i ) {
     throw new UnsupportedOperationException("Not implemented.");
   }
   public T get( int i, int j ) {
     throw new UnsupportedOperationException("Not implemented.");
   }
   public T get( int ... i ) {
     throw new UnsupportedOperationException("Not implemented.");
   }
 }

This is how AbstractList and the other abstract collections work. Most
methods throw an exception. You override them if you need them,
otherwise you just don't call them.


I expect the mutator methods of an immutable collection to throw
UnsupportedOperationExceptions - that's a little under half. I don't
expect the other methods, or any methods of a mutable collection, to do
so. I'd be surprised and annoyed to have a class that did so.

You're proposing a class where *two thirds* of the methods will always
throw such an exception. Surely this is the design screaming out to us to
be factored into three separate classes?

tom

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