Book notes

The Template Method Pattern defines the skeleton of an algorithm in a method, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm’s structure.

Key points:

• A template method defines the steps of an algorithm, deferring to subclasses for the implementation of those steps.
• The Template Method Pattern gives us an important technique for code reuse
• The template method’s abstract class may define concrete methods, abstract methods, and hooks.
• Abstract methods are implemented by subclasses.
• Hooks are methods that do nothing or default behavior in the abstract class, but may be overridden in the subclass.
• To prevent subclasses from changing the algorithm in the template method, declare the template method as final.
• The Hollywood Principle guides us to put decision making in high level modules that can decide how and when to call low-level modules.
• Factory Method is a specialization of Template Method.

Example