Template Method Pattern

in Design Patterns
Template Method Pattern

Template Method Pattern에 대해 설명하는 페이지입니다.

Environment

  • Programming Language: Java

Index

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.

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.

Hook Method

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

How to Use (Example)

  • Superclass
    public abstract class CaffeineBeverage {
    public void final prepareRecipe() {
        boilWater();
        brew();
        pourInCup();
        if (customerWantsCondiments()) {
            addCondiments();
        }
    }

    public void boilWater() {
        // implementation
    }

    public abstract void brew();

    public void pourInCup() {
        // implementation
    }

    public abstract void addCondiments();

    // hook
    public boolean customerWantsCondiments() {
        return true;
    }
}
  • Subclass
    public class Coffee extends CaffeineBeverage {
    @Override
    public void brew() {
        // implementation
    }

    @Override
    public void addCondiments() {
        // implementation
    }

    @Override
    public boolean customerWantsCondiments(char c) {
        if (c == 'y') {
            return true;
        } else {
            return false;
        }
    }
}




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