> -----Original Message----- > From: Takuya Murata [mailto:[EMAIL PROTECTED] > Sent: 20 August 2003 04:29 > To: Jakarta Commons Developers List > Subject: Re: [collections] Questions.... > > > Hi, > > So the question is do we really need SingletonIterator and > such. If we > want to eliminate the number of methods or classes, then what > about one > class for all of collections or iterators? I suppose the use of > singleton methods and classes is almost always to provide an object > matching a data type you want. Thus, we can have a class like > > class Singleton implements List, SortedSet, Bag, Iterator, > ListIterator > { > }
this sounds hugely dangerous - the javadocs for List#equals(Object) for example stipulate: Compares the specified object with this list for equality. Returns true if and only if the specified object is also a list, both lists have the same size, and all corresponding pairs of elements in the two lists are equal. (Two elements e1 and e2 are equal if (e1==null ? e2==null : e1.equals(e2)).) In other words, two lists are defined to be equal if they contain the same elements in the same order. This definition ensures that the equals method works properly across different implementations of the List interface. whereas Set#equals(Object) state: Compares the specified object with this set for equality. Returns true if the specified object is also a set, the two sets have the same size, and every member of the specified set is contained in this set (or equivalently, every member of this set is contained in the specified set). This definition ensures that the equals method works properly across different implementations of the set interface. This is only one of many conflicts. Just implementing the method signatures of such classes without implementing their 'contracts' (even if the contract is only the official line on what they should and shouldn't do) is a recipe for confusion and bugs... Matt ************************************************************************** The information transmitted herewith is sensitive information intended only for use by the individual or entity to which it is addressed. If the reader of this message is not the intended recipient, you are hereby notified that any review, retransmission, dissemination, distribution, copying or other use of, or taking of any action in reliance upon this information is strictly prohibited. If you have received this communication in error, please contact the sender and delete the material from your computer. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
