Design Patterns Java™ Workbook

Summary

The intent of the ITERATOR pattern is to let a client access the elements of a collection sequentially. The collection classes in the Java class libraries offer rich support for operating on collections, including support for iteration. These iterators usually require a client to cast the returned objects to the appropriate type. You can strengthen your contract with clients by creating type-specific collections with type-specific iterators.

If you create a new type of collection, you will often want to create an iterator to go with it. Domain-specific composites are a common example of a new collection type. You can design a fairly generic iterator for composites that you may be able to apply against a variety of composite hierarchies. ...