常用设计模式

一.单例模式：

public class Singleton {  
    private static Singleton instance;  
    private Singleton (){}  
    public static Singleton getInstance() {  
      if (instance == null) {  
          instance = new Singleton();  
      }  
      return instance;  
    }  
}

二.观察着模式：

public interface Person {
    //老王和老李通过这个接口可以接收到小美发过来的消息
    void getMessage(String s);
}

public class LaoWang implements Person {
    private String name = "老王";
    public LaoWang() {}
    @Override
    public void getMessage(String s) {
        System.out.println(name + "接到了小美打过来的电话，电话内容是：" + s);
    }
}

public class LaoLi implements Person {
    private String name = "老李";
    public LaoLi() {}
    @Override
    public void getMessage(String s) {
        System.out.println(name + "接到了小美打过来的电话，电话内容是：->" + s);
    }
}

public class XiaoMei {
    List<Person> list = new ArrayList<Person>();
      public XiaoMei(){}
      public void addPerson(Person person){
               list.add(person);
      }
      //遍历list，把自己的通知发送给所有暗恋自己的人
       public void notifyPerson() {
           for(Person person:list){
　　　　　　　　person.getMessage("我是广播，我发消息了哈");
           }
       }
}

public class Test {
  public static void main(String[] args) {
          XiaoMei xiao_mei = new XiaoMei();
          LaoWang lao_wang = new LaoWang();
        LaoLi lao_li = new LaoLi();
        //老王和老李在小美那里都注册了一下
        xiao_mei.addPerson(lao_wang);
          xiao_mei.addPerson(lao_li);
        //小美向老王和老李发送通知
        xiao_mei.notifyPerson();
    }
}

三.装饰器模式

public class Food {
   private String food_name;
   public Food() {}
   public Food(String food_name) {
        this.food_name = food_name;
    }
    public String make() {
        return food_name;
    }
}

//面包类
public class Bread extends Food {
    private Food basic_food;
    public Bread(Food basic_food) {
        this.basic_food = basic_food;
    }
    public String make() {
        return basic_food.make()+"+面包";
    }
}

//奶油类
public class Cream extends Food {
    private Food basic_food;
    public Cream(Food basic_food) {
        this.basic_food = basic_food;
    }
    public String make() {
        return basic_food.make()+"+奶油";
    }
}

//蔬菜类
public class Vegetable extends Food {
    private Food basic_food;
    public Vegetable(Food basic_food) {
        this.basic_food = basic_food;
    }
    public String make() {
        return basic_food.make()+"+蔬菜";
    }
}

//测试：
public class Test {
    public static void main(String[] args) {
        Food food = new Bread(new Vegetable(new Cream(new Food("香肠"))));
        System.out.println(food.make());
    }
}

四.适配器模式

public class Test {
    public static void main(String[] args) {
        Phone phone = new Phone();
        VoltageAdapter adapter = new VoltageAdapter();
        phone.setAdapter(adapter);
        phone.charge();
    }
}

// 手机类
class Phone {
    public static final int V = 220;// 正常电压220v，是一个常量
    private VoltageAdapter adapter;
    // 充电
    public void charge() {
        adapter.changeVoltage();
    }
    public void setAdapter(VoltageAdapter adapter) {
        this.adapter = adapter;
    }
}

// 变压器
class VoltageAdapter {
    // 改变电压的功能
    public void changeVoltage() {
        System.out.println("正在充电...");
        System.out.println("原始电压：" + Phone.V + "V");
        System.out.println("经过变压器转换之后的电压:" + (Phone.V - 200) + "V");
    }
}

五．代理模式

//代理接口
public interface ProxyInterface {
   //需要代理的是结婚这件事
   void marry();
}

婚庆公司的代码:
public class WeddingCompany implements ProxyInterface {
   private ProxyInterface proxyInterface;
   public WeddingCompany(ProxyInterface proxyInterface) {
      this.proxyInterface = proxyInterface;
   }

 @Override
   public void marry() {
      System.out.println("我们是婚庆公司的");
      System.out.println("我们在做结婚前的准备工作");
      System.out.println("节目彩排...");
      System.out.println("礼物购买...");
      System.out.println("工作人员分工...");
      System.out.println("可以开始结婚了");
      proxyInterface.marry();
      System.out.println("结婚完毕，我们需要做后续处理，你们可以回家了，其余的事情我们公司来做");
   }

}

结婚家庭
public class NormalHome implements ProxyInterface{
   @Override
   public void marry() {
      System.out.println("我们结婚啦～");
   }
}