Java设计模式（一）

talk is cheap show me the code

单例模式

• 懒汉模式

 class Singleton{
        private static final Singleton instance = null;

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

• 恶汉模式

class Singleton{
        private static final Singleton instance = new Singleton;

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

• 线程安全模式

class Singleton{
        private static final Singleton instance = null;

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

工厂模式

• 简单工厂模式

interface SimpleProduct{
          void doSomething();
}

class ProductA extends SimpleProduct{
          public void doSomething(){
                system.out.println("this is Product A");
          }
}

class ProductB extends SimpleProduct{
          public void doSomething(){
                system.out.println("this is Product B");
          }
}

class SimpleFactory{
        public static SimpleProduct getProduct(String name){
                    if(name.equals("A"))
                            return new ProductA();
                    else return new ProductB();
        }
}

• 工厂方法模式

interface SimpleProduct{
          void doSomething();
}

class ProductA extends SimpleProduct{
          public void doSomething(){
                system.out.println("this is Product A");
          }
}

class ProductB extends SimpleProduct{
          public void doSomething(){
                system.out.println("this is Product B");
          }
}

class MethodFactory{
        public static SimpleProduct getProductA(){
                     return new ProductA();
        }

        public static SimpleProduct  getProductB(){
                     return new ProductB();
        }
}

• 抽象工厂模式

interface SimpleProduct{
          void doSomething();
}

class ProductA extends SimpleProduct{
          public void doSomething(){
                system.out.println("this is Product A");
          }
}

class ProductB extends SimpleProduct{
          public void doSomething(){
                system.out.println("this is Product B");
          }
}


##将工厂抽象成接口
interface AbstractFactory{
      SimpleProduct getProduct();
}

class FactoryA implements AbstractFactory{
    SimpleProduct getProduct(){
           return new ProductA();
    }
}

建造者模式

• 建造者模式

class Computer{
      private String cpu;

      private String disk;

      private Computer setCpu(String cpu){
                  this.cpu = cpu;
                  return this;
      }
}