模板方法模式——Head First Design Patterns

定义：模板方法定义了一个算法的步骤，并且允许子类重载某些步骤。

 

使用场景：算法的总体步骤基本稳定，但是某些步骤的具体算法经常改变

 

类图：

代码样例：

 

package headfirst.templatemethod.barista;public abstract class CaffeineBeverageWithHook { void prepareRecipe() {boilWater();brew();pourInCup();if (customerWantsCondiments()) {addCondiments();}} abstract void brew(); abstract void addCondiments(); void boilWater() {System.out.println("Boiling water");} void pourInCup() {System.out.println("Pouring into cup");} boolean customerWantsCondiments() {return true;}}

package headfirst.templatemethod.barista;import java.io.*;public class CoffeeWithHook extends CaffeineBeverageWithHook { public void brew() {System.out.println("Dripping Coffee through filter");} public void addCondiments() {System.out.println("Adding Sugar and Milk");} public boolean customerWantsCondiments() {String answer = getUserInput();if (answer.toLowerCase().startsWith("y")) {return true;} else {return false;}} private String getUserInput() {String answer = null;System.out.print("Would you like milk and sugar with your coffee (y/n)? ");BufferedReader in = new BufferedReader(new InputStreamReader(System.in));try {answer = in.readLine();} catch (IOException ioe) {System.err.println("IO error trying to read your answer");}if (answer == null) {return "no";}return answer;}}

 

优点：1）规范化算法步骤，总体框架趋于稳定，防止代码五花八门，便于大家理解代码；2）抽象出总体步骤，减少开发者思考时间，提升开发效率 3）

缺点：1）模板方法改变，所有的子类都可能会受影响

 

类似的设计模式：

见工厂方法设计模式 

 

配套的内功心法：1）好莱坞原则：不要找我，我会找你；即让高层次代码决定何时调用低层次代码，而低层次代码实现具体的算法以组成具体系统。