java设计模式——结构型模式（二）

Hello 帅帅 2021-02-05

531

外观模式

例：定义一个动物接口，猫狗鱼实现该接口，并有购买方法，超市类，该类在构造时便创建了之前动物类的对象，并且可以调用动物类的方法。

Animal

 public interface Animal {
     void buy();
 }

Cat

 public class Cat implements Animal{
     public void buy(){
         System.out.println("你买了一只猫");
     }
 }

Dog

 public class Dog implements Animal{
    public void buy() {
         System.out.println("你买了一条狗");
     }
 }

Fish

 public class Fish implements Animal {
     public void buy(){
         System.out.println("你买了鱼老师");
     }
 }

Market

 public class Market {
     private final Cat cat;
     private final Dog dog;
     private final Fish fish;
 
     public Market() {
          cat = new Cat();
          dog = new Dog();
          fish = new Fish();
     }
 
 
     public void buyCat() {
         cat.buy();
     }
 
     public void buyDog() {
         dog.buy();
     }
 
     public void buyFish() {
         fish.buy();
     }
 }

Test

 public class Test {
     public static void main(String[] args) {
         Market m=new Market();
 
         m.buyCat();
         m.buyDog();
         m.buyFish();
     }
 }

享元模式

例：MyBook实现book接口，有属性name。Bookcase有获取书籍方法，如果书架中有相应书籍，则返回相应hashmap中相应书籍，如果没有相应书籍，则new一个MyBook对象，并将其加入到hashmap中

Book

 public interface Book {
     void look();
 }

Bookcase

 public class Bookcase {
     Map<String, MyBook> m = new HashMap<>();
 
     public Book getBook(String name) {
         if (!m.containsKey(name)) {
             m.put(name, new MyBook(name));
         }
         return (Book) m.get(name);
     }
 
     public int count(){
         return m.size();
     }
 }

MyBook

 public class MyBook implements Book {
     private final String name;
 
     public MyBook(String name) {
         this.name = name;
     }
 
     @Override
     public void look() {
         System.out.println("你正在看书：" + name);
     }
 }

Test

 public class Test {
     public static void main(String[] args) {
         Bookcase bookcase = new Bookcase();
 
         bookcase.getBook("三国演义");
         bookcase.getBook("三国演义");
         bookcase.getBook("三国演义");
         bookcase.getBook("三国演义");
 
         bookcase.getBook("水浒传");
         bookcase.getBook("水浒传");
         bookcase.getBook("水浒传");
         bookcase.getBook("水浒传");
 
         System.out.println(bookcase.count());
     }
 }

代理模式

例：代理图片与真实图片实现图片接口，真实图片在创建时，会在内存中加载，代理图片在加载时，如果之前加载过，则不会消耗时间在内存中加载。Image

 public interface Image {
     void display();
 }

ProxyImage

 public class ProxyImage implements Image {
 
     private final String name;
     private RealImage realImage;
 
     public ProxyImage(String name) {
         this.name = name;
     }
 
     @Override
     public void display() {
         if (realImage == null) {
             realImage = new RealImage(this.name);
         }
         realImage.display();
     }
 }

RealImage

 public class RealImage implements Image {
 
     private final String name;
 
     public RealImage(String name) {
         this.name = name;
         load();
     }
 
     private void load() {
         System.out.println("加载图像，消耗两秒");
         try {
             Thread.sleep(2000);
         } catch (InterruptedException e) {
             e.printStackTrace();
         }
     }
 
     @Override
     public void display() {
         System.out.println("显示图片");
     }
 }

Test

 public class Test {
     public static void main(String[] args) {
         Image image1 = new ProxyImage("图片1");
 
         image1.display();
         image1.display();
         image1.display();
         image1.display();
     }
 }

java

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java设计模式——结构型模式（二）

外观模式

享元模式

代理模式

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