Quick Reference

Note:

• The intention of this guide is to be succinct. Don't use this for extended explanation, just note brief points. People can follow links for explanation.
• While this guide may be useful for the exam, don't be exam specific. This is a concise list of concepts to jog your memory, not a Cheat Sheet with direct answers from last year or whatever.

Contradictory Design Maxims

• Design by contract and Tell, don't ask
• Composite pattern and Avoid no-op overrides

Design Pattern Cliff Notes

• Decorator
  • Identify by: Both HAS A and IS A at the same time, with multiple subclasses.
  • Used for: Adding flexible combinations of specialized functionality.
  • Classic Example: Adding scrolling functionality, borders, etc to a window.
  • Why better than alternatives: Avoids combinatorial explosion of subclasses.

• Composite
  • Identify by: Both HAS A and IS A at the same time, usually without subclasses.
  • Used for: Making many act as one.
  • Classic Example: Making a shape comprising other shapes.
  • Why better than alternatives: Can use singular and collective instances totally transparently (identically).