设计模式

桥接模式（Bridge）

• 介绍：将抽象与实现分离开来，使它们可以独立变化。

• 关系图：

  

  将品牌和类型分开。

  1. 品牌接口

  public interface Brand {
      void info();
  }

  2. 实现品牌接口

  public class Apple implements Brand {
      @Override
      public void info() {
          System.out.print("苹果");
      }
  }
  

  public class Lenovo implements Brand {
      @Override
      public void info() {
          System.out.print("联想");
      }
  }
  

3. 电脑类型抽象类

   public abstract class Computer {
    private Brand brand;
   
    public Computer(Brand brand) {
        this.brand = brand;
    }
    public void info(){
        brand.info();
    }
   }

4. 继承电脑类型类

   class Desktop extends Computer{
   
    public Desktop(Brand brand) {
        super(brand);
    }
   
    @Override
    public void info() {
        super.info();
        System.out.print("台式机");
    }
   }
   class Laptop extends Computer{
   
    public Laptop(Brand brand) {
        super(brand);
    }
   
    @Override
    public void info() {
        super.info();
        System.out.print("笔记本");
    }
   }

5. 测试类

   public class Test {
    public static void main(String[] args) {
        Computer computer =new Desktop(new Apple()) ;
        computer.info();
        Computer computer1=new Laptop(new Lenovo());
        computer1.info();
    }
   }
   //苹果台式机联想笔记本

   

单例模式

//饿汉模式
public class SingletonDemo1 {
    private  SingletonDemo1(){}

    private static SingletonDemo1 instance = new SingletonDemo1();

    public static  SingletonDemo1 getInstance(){
        return instance;
    }


}

//懒汉式
public class SingletonDemo2 {
    //私有化构造器
    private SingletonDemo2(){
    }
    //类初始化不立即加载该对象
    private  static SingletonDemo2 instance;
    // synchronized 效率低 //JVM 指令重排，某些线程获得未实例化对象
    public static synchronized SingletonDemo2 getInstance(){
        if (instance==null){
            instance = new SingletonDemo2();
        }
        return instance;
    }
}

// 双重检测/懒汉式
public class SingletonDemo3 {
    //
    private   SingletonDemo3(){

    }
    private volatile static  SingletonDemo3 instance; //voaltile（） 排除JVM指令重排产生的影响
    public static  SingletonDemo3 getInstance(){
        if (instance==null){
            synchronized (SingletonDemo3.class){ //线程竞争锁
                if (instance==null){//竞争到后再判断对象是否实例化
                    instance=new SingletonDemo3();  //1.为 instance 分配内存空间
                                                    //1.初始化 instance
                                                    //3.将 instance 指向分配的内存地址
                }
            }
        }
        return instance;
    }
}

//静态内部类实现
public class SingletonDemo4 {
    private SingletonDemo4(){
    }

    private static class InnerClass{
        private static final SingletonDemo4 instance =new SingletonDemo4();
    }
    //延迟加载
    public static  SingletonDemo4 getInstance(){
        return InnerClass.instance;
    }

}

//枚举实现
public enum SingletonDemo5 {
    INSTANCE;
    public SingletonDemo5 getInstance(){
        return INSTANCE;
    }
}