Template Method Pattern

Template Method Pattern에 대해 설명하는 페이지입니다.

Posted Dec 25, 2023

By HyunJinNo

Tags

Design Pattern, Java

1. Introduction

• Purpose
  • Identifies the framework of an algorithm, allowing implementing classes to define the actual behavior.
• Use When
  • A single abstract implementation of an algorithm is needed.
  • Common behavior among subclasses should be localized to a common class.
  • Parent classes should be able to uniformly invoke behavior in their subclasses.
  • Most or all subclasses need to implement the behavior.

2. Characteristics

• The template pattern defines the steps of an algorithm and allows the subclasses to implement one or more of the steps.
• Encapsulates an algorithm by creating a template for it.
• Defines the skeleton of an algorithm as a set of steps.
• Some methods of the algorithm have to be implemented by the subclasses– these are abstract methods in the super class.
• The subclasses can redefine certain steps of the algorithm without changing the algorithm’s structure.
• Some steps of the algorithm are concrete methods defined in the super class.
• Advantages
  • The superclass facilitates reuse of methods.
  • Code changes will occur in only one place.

3. Hook Method

• A hook is a method that is declared in the abstract class, but only given an empty or default implementation.

4. How to Use (Example)

• Superclass

  java

  1public abstract class CaffeineBeverage {
  2    public void final prepareRecipe() {
  3        boilWater();
  4        brew();
  5        pourInCup();
  6        if (customerWantsCondiments()) {
  7            addCondiments();
  8        }
  9    }
  10
  11    public void boilWater() {
  12        // implementation
  13    }
  14
  15    public abstract void brew();
  16
  17    public void pourInCup() {
  18        // implementation
  19    }
  20
  21    public abstract void addCondiments();
  22
  23    // hook
  24    public boolean customerWantsCondiments() {
  25        return true;
  26    }
  27}

• Subclass

  java

  1public class Coffee extends CaffeineBeverage {
  2    @Override
  3    public void brew() {
  4        // implementation
  5    }
  6
  7    @Override
  8    public void addCondiments() {
  9        // implementation
  10    }
  11
  12    @Override
  13    public boolean customerWantsCondiments(char c) {
  14        if (c == 'y') {
  15            return true;
  16        } else {
  17            return false;
  18        }
  19    }
  20}