２．Java设计模式－－＞观察者模式

这是根据别人文章，自己整理过来的．原文链接：

一：简单工厂模式

BMW.javapublic interface BMW{}

BMW320.javapublic class BMW320 implements BMW{    public BMW320(){    System.out.println("BMW320 has been made already");    }}

BMW520.javapublic class BMW520 implements BMW{    public BMW520(){    System.out.println("BMW520 has been made already");    }}

Factory.javapublic class Factory {    public BMW creatBMW(int type){//工厂只是提供一个方法    swith(type){//根据选择进行实例化    case 320:        return new BMW320();    case 520:        return new BMW520();    default:        break;        }    return null;//确保返回规定返回值，否则编译不通过    }}

Test.javapublic class Test{    public static void main( string[] args){    Factory factory = new Factory();    BMW bmw320 = factory.createBMW( 320);    BMW bmw520 = factory.createBMW( 520);    }

二：工厂方法

BMW.javapublic interface BMW{}

BMW320.javapublic class BMW320 implements BMW{    public BMW320(){    System.out.println("BMW320 has beed made already");    }}

BMW520.javapublic class BMW520 implements BMW{    public BMW520(){    System.out.println("BMW520 has been made already");    }}

．．．．．．．．．．．．．．以上代码与简单工厂一致

Factory.javapublic interface Factory{    BMW creatBMW();//接口中方法默认修饰符：public abstract    }

FactoryBMW320.javapublic class FactoryBMW320 implements Factory{    @Override //覆盖:１返回值　２．方法名　３．参数    public BMW320 createBMW(){//关于此行的 public　修饰符．一般覆盖都是由子类完成．能继承的变量只要 protected 和 public.改写修饰符也是只能放低门槛，所以 protected的变量也会变成　public.一般情况下，需要覆盖的方法的修饰符是不进行调整的，基本是 public.        return new BMW320();        }    }

FactoryBMW520.javapublic class FactoryBMW520 implements Factory{    @Override    public BMW520 createBMW(){        return new BMW520();        }    }

Test.javapublic class Test{    public static void main( String[] args){    Factory factory320 = new FactoryBMW320();    Factory factory520 = new FactoryBMW520();    BMW bmw320 = factory320.createBMW();    BMW bmw520 = factory520.createBMW();    }

主要是进行工厂的解耦，让特定工厂生产特定产品．

三抽象工厂

Engine.javapublic interface Engine{//interface 默认属性：public static final.此行的 pulic 可以省略．}

EngineA.javapublic class EngineA implements Engine{    public EngineA(){    System.out.println("equipped with EngineA");    }}

EngineB.javapublic class EngineB implements Engine{    public EngineB(){    System.out.println("equipped with EngineB");    }}

引擎系列产品

Aircondition.javainterface Aircondition{}

AirconditionA.javapublic class AirconditionA implements Aircondition{    public AirconditionA(){    System.out.println("equipped with airconditon A ");    }}

AirconditionB.javapublic class AirconditionB implements Aircondition{    public AirconditionB(){    System.out.println("equipped with airconditin B");    }}

空调系列产品的制造

AbstractFactory.javainterface AbstractFactory{    Engine createEngine();    Aircondition createAircondition();    }//明显，我们也可以在其中建造BMW,工厂方法已实验过，不再添加

FactoryBMW320.javapublic class FactoryBMW320 implements AbstractFactory{    public EngineA createEngine(){//此行要加public,否则使用门槛升高到 default,编译不能通过．可以指定返回值的子类．        return new EngineA();        }    public AirconditionA createAircondition(){        return new AirconditionA();        }

相同地：

FactoryBMW520.javapublic class FactoryBMW520 implements AbstractFactory{    public EngineB createEngine(){        return new EngineB();        }    public AirconditionB createAircondition(){        return new AirconditonB();        }    }

最后，测试．

Test.javapublic class Test{    public static void main ( String[] args ){    FactoryBMW320 factory = new FactoryBMW320();    factory.createEngine();    factory.createAircondition();//生产出a型引擎，空调．