Design Patterns Java™ Workbook

Summary

COMPOSITE contains two powerful, related concepts. One concept is that a group can contain either individual items or other groups. Related to this concept is the idea that groups and individual items may share a common interface. These ideas come together in object modeling, whereby you can create an abstract class or a Java interface that defines the behaviors that are common to groups and to individual objects.

Modeling composites often leads to recursive definition of methods on composite nodes. When recursion is present, a danger exists of writing code that produces an infinite loop. To avoid such problems, you can take steps to guarantee that your composites are always trees. Alternatively, you can allow cycles to occur in a composite, ...