Design Patterns Java™ Workbook

Appendix B. Solutions

Chain of Responsibility (Chapter 12)......................................................................................................

SOLUTION 12.1....................................................................................................................................

Two possible answers follow.

• Method lookup searches across a well-defined series of classes. The CHAIN OF
  RESPONSIBILITY pattern directs the search for a responsible method to occur across
  a series of objects.


• The mechanics of method lookup are part of the Java language specification, whereas
  CHAIN OF RESPONSIBILITY is under your control as a developer.

SOLUTION 12.2....................................................................................................................................

Your diagram should looking similar to Figure B.16. With this design, any client of
any simulated item can simply ask the item for the responsible engineer. As the next
challenge shows, the code for the various implementations of getResponsible() gets
simpler, too.

Figure B.16. Every SimlulatedItem object can respond to a getResponsible() call.

Internally, a Simulated-Item object may forward the request to its parent.