设计模式

六大原则

• 开闭原则
• 扩展性
• 易于修改
• 里式代换原则
• 依赖倒转原则
• 接口隔离原则

常见的几种设计模式

• 单例模式

  懒汉式:

  class Singleton{
    static private Singleton singleton = null;
    public  Singleton getSingleton() {
        if (singleton == null) {// 第一层上锁
            synchronized (Singleton.class) {
                if(singleton==null) // 第二层上锁  双重检验锁
                singleton = new Singleton();
            }
  
        }
        //当对象不是Null时候不用考虑线程安全了
        return singleton;
    }
  }

  饿汉式:

  class Singleton{
    static private Singleton singleton = new Singleton();
    public  Singleton getSingleton() {
        if (singleton == null) {// 第一层上锁
            synchronized (Singleton.class) {
                if(singleton==null) // 第二层上锁  双重检验锁
                singleton = new Singleton();
            }
  
        }
        //当对象不是Null时候不用考虑线程安全了
        return singleton;
    }
  }

• 工厂模式

  简单工厂:

  interface Car {void run();}
  class AoDi implements Car {
  @Override public void run() {
        System.out.println("我是奥迪汽车---我是奥迪A6l");}}
  class BenChi implements Car {
  @Override public void run() {
        System.out.println("我是奔驰汽车----我是奔驰E级");}}
  
  // 奔驰工厂
  class BenChiFatory {
    static public Car createCar() {
        return new BenChi();
    }}
  
  class AoDiFatory {
    static public Car createCar() {
        return new AoDi();
    }}
  
  class CarFatory {
    static public Car createCar(String name) {
        Car car = null;
        switch (name) {
        case "奥迪":
            car = new AoDi();
            break;
        case "奔驰":
            car = new BenChi();
            break;
        default:
            break;
        }
        return car;
    }
  }
  
  public class Test005 {
    public static void main(String[] args) {
        Car car = BenChiFatory.createCar();
        car.run();
        // Car car = CarFatory.createCar("奔驰");
        // car.run();
    }
  }

  抽象工厂:

• 代理模式

  静态代理:

  class YuShengJun implements Hose {
  
    @Override
    public void maifang() {
        System.out.println("我是余胜军，终于可以买房啦!!!");
    }
  
  }
  
  // 静态代理
  class Proxy implements Hose {
    // 代理对象
    private YuShengJun yuShengJun;
  
    public Proxy(YuShengJun yuShengJun) {
        this.yuShengJun = yuShengJun;
    }
  
    @Override
    public void maifang() {
        System.out.println("我是中介,你买房开始交给我啦!!!");
        yuShengJun.maifang();
        System.out.println("我是中介,你买房开结束啦!!!");
    }
  
  }

  动态代理:

  // jdk动态代理
  class JdkProxy implements InvocationHandler {
    private Object tarjet;
  
    JdkProxy(Object tarjet) {
        this.tarjet = tarjet;
    }
  
    @Override
    public Object invoke(Object paramObject, Method paramMethod, Object[] paramArrayOfObject) throws Throwable {
  
        System.out.println("我是中介,你买房开始交给我啦!!!");
        Object invoke = paramMethod.invoke(tarjet, paramArrayOfObject);
        System.out.println("我是中介,你买房开结束啦!!!");
        return invoke;
  
    }
  
  }
  
   //cglib 动态代理
  class Cglib implements MethodInterceptor{
  
    @Override
    public Object intercept(Object oj, Method method, Object[] arrays, MethodProxy methodProxy) throws Throwable {
  
        System.out.println("我是中介,你买房开始交给我啦!!!");
        Object invokeSuper = methodProxy.invokeSuper(oj, arrays);
        System.out.println("我是中介,你买房开结束啦!!!");
         return invokeSuper;  
  
    }
  
  
  }
  
  public class Test006 {
    public static void main(String[] args) {
  //        Hose hose = new Proxy(new YuShengJun());
  //        hose.maifang();
        YuShengJun yuShengJun = new YuShengJun();
  //        JdkProxy jdkProxy = new JdkProxy(yuShengJun);
  //        Hose hose = (Hose) java.lang.reflect.Proxy.newProxyInstance(yuShengJun.getClass().getClassLoader(), yuShengJun.getClass().getInterfaces(), jdkProxy);
  //        hose.maifang();
        Cglib cglib = new Cglib();
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(YuShengJun.class);
        enhancer.setCallback(cglib);
        Hose hose = (Hose) enhancer.create();
        hose.maifang();
  
    }
  }

设计模式

原文：https://www.cnblogs.com/MagicalFool/p/12288587.html