Introduction to Programming

Answer

The four patterns—one from each of the four categories—could be the following:

• Creational patterns: Factory method
• Structural patterns: Composite
• Behavioral patterns: Visitor
• Concurrency patterns: Messaging pattern

In this book, we have already used the following patterns:

• Lazy initialization: In Chapter 6, Interfaces, Classes, and Object Construction, we initialized the SingletonClassExample OBJECT static field, not automatically, but only when the getInstance() method was called
• Singleton: In Chapter 6, Interfaces, Classes, and Object Construction, see the SingletonClassExample class
• Facade: In Chapter 6, Interfaces, Classes, and Object Construction, when we created a Calculator interface that captures all possible interactions ...