模版模式 读书笔记

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在一个方法中定义一个算法的骨架，而将一些步骤延迟到子类中。模版方法使子类可以在不改变算法结构的情况下，重新定义算法中的某些步骤。模板就是一个方法。更具体的说，这个方法将算法定义成一组步骤，其中的任何步骤都可以是抽象的，由子类负责实现。这可以确保算法的结构保持不变，同时由子类提供部分实现。
1 。模版方法定义了算法的步骤，把这些步骤地实现延迟到子类。
2。模版方法模式为我们提供了一种代码复用的重要技巧。
3。模版方法的抽象类可以定义具体的方法，抽象的方法和钩子。
4。抽象方法由子类实现。
5。钩子是一种方法，它在抽象类中不做事，或者只做默认的事情，资料可以选择要不要去覆盖它。
6。为了防止子类改变模版方法中的算法，可以将模版声明为final。
7。好莱坞原则告诉我们，将决策权放在高层模块中，以便决定如何以及何时调用底层模块。
8。你将在真实世界 代码中看到模版方法模式的许多变体，不要期待他们全部是 一眼就可以被你认出的。
9。策略模式和模版方法模式都封装算法，一个用组合一个用继承。
10。工厂方法是模版方法的一种特殊版本。

package pattern;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public abstract class CaffeineBeverage {
 final void prepareRecipe(){
  boilWater();
  brew();
  pourInCup();
  addCondiments();
 }
 abstract void brew();
 abstract void addCondiments();
 void boilWater(){
  System.out.println("Boiling water");
 }
 void pourInCup(){
  System.out.println("Pouring into cup");
 }
}
class Tea extends CaffeineBeverage{
 public void brew(){
  System.out.println("Steeping the tea");
 }
 public void addCondiments(){
  System.out.println("Adding Lemon");
 }
}
class Coffee extends CaffeineBeverage{
 public void brew(){
  System.out.println("Dripping Coffee  through filter");
 }
 public void addCondiments(){
  System.out.println("Adding Sugar and Milk");
 }
} 
 abstract class CaffeineBeverageWithHook {
 final 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;
 }
}
class TeaWithHook extends CaffeineBeverageWithHook{
 public void brew(){
  System.out.println("Steeping the tea");
 }
 public void addCondiments(){
  System.out.println("Adding Lemon");
 }
}
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.println("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;
 }
} 
 
package pattern;
public class BeverageTestDrive {
 public static void main(String[] args) {
  TeaWithHook teaHook=new TeaWithHook();
  CoffeeWithHook coffeeHook=new CoffeeWithHook();
  System.out.println("\nMaking tea...");
  teaHook.prepareRecipe();
  System.out.println("\nMaking coffee...");
  coffeeHook.prepareRecipe(); 
 }
}

 
package pattern;
import java.util.Arrays;
public class DuckSortTestDrive {
 public static void main(String[] args) {
  DuckSort[] ducks = { new DuckSort("Daffy", 8),
    new DuckSort("Dewey", 2), new DuckSort("Howard", 7),
    new DuckSort("Louie", 2), new DuckSort("Donald", 10),
    new DuckSort("Huey", 2) };
  System.out.println("Bdfore sorting:");
  display(ducks);
  Arrays.sort(ducks);
  System.out.println("\nAfter sorting:");
  display(ducks);
 }
 static void display(DuckSort[] ducks) {
  for (int i = 0; i < ducks.length; i++) {
   System.out.println(ducks[i]);
  }
 }
}
class DuckSort implements Comparable {
 String name;
 int weight;
 public DuckSort(String name, int weight) {
  this.name = name;
  this.weight = weight;
 }
 public String toString() {
  return name + " weighs " + weight;
 }
 public int compareTo(Object object) {
  DuckSort otherDuck = (DuckSort) object;
  if (this.weight < otherDuck.weight) {
   return -1;
  } else if (this.weight == otherDuck.weight) {
   return 0;
  } else {
   return 1;
  }
 }
}
 
package pattern;
public class DuckTestDrive {
 public static void main(String[] args) {
  DuckInterface duck=new MallardDuckinterface();
  WildTurkey turkey= new WildTurkey();
  
  DuckInterface turkeyAdapter=new TurkeyAdapter(turkey);
  Turkey duckAdapter=new DuckAdapter(duck);
  System.out.println("The Turkey says...");
  turkey.gobble();
  turkey.fly();
  
  System.out.println("\n The Duck says...");
  testDuck(duck);
  
  System.out.println("\n The TurkeyAdapter says...");
  //testDuck(turkeyAdapter);
  //turkeyAdapter.quack();
  duckAdapter.fly();
 }
 static void testDuck(DuckInterface duck){
  duck.quack();
  duck.fly();
 }
}