java8提供了很多新的特性，可以用来重构传统设计模式中的写法。下面是一些例子：1.策略模式上图是策略模式的类图。假设我们现在要保存订单，OrderService接口定义了Whattodo，而NoSqlSaveOrderStragegy和MySqlSaveOrderStrategy提供了两种策略，保存到nosql数据库和传统的mysql关系数据库，最后注入最终要用到的策略OrderServiceExecutor通过构造函数。传统写法，这个场景至少需要4个类，代码如下：OrderService接口：publicinterfaceOrderService{voidsaveOrder(StringorderNo);}orderNo){System.out.println("订单："+orderNo+"保存到mysql");}}Nosql策略实现：publicclassNoSqlSaveOrderStrategyimplementsOrderService{@OverridepublicvoidsaveOrder(StringorderNo){System.out.println("order:"+orderNo+"savetonosql");}}辅助“容器”使用策略：publicclassOrderServiceExecutor{privatefinalOrderServiceservice;publicOrderServiceExecutor(OrderServiceservice){this.service=service;}publicvoidsave(StringorderNo){this.service.saveOrder(orderNo);}}运行测试类：公共类OrderServiceTest{publicstaticvoidmain(String[]args){执行器1.save("001");OrderServiceExecutorexecutor2=newOrderServiceExecutor(newNoSqlSaveOrderStrategy());executor2.save("002");}}重构后可以省去2个策略实现类，代码如下：:"+orderNo+"保存到mysql"));executor1.save("001");OrderServiceExecutorexecutor2=newOrderServiceExecutor((StringorderNo)->System.out.println("order:"+orderNo+"保存到nosql"));executor2.save("002");}2.模板方法类图如下，核心思想是在抽象父类中定义一些常用的标准方法，只定义方法签名，实现逻辑交给子类。例如：在会员系统中，每个商家都会有一些营销活动，需要向会员推送一定的信息，但是不同的商家推送的内容可能会有所不同。有的需要推送优惠券，有的需要积分通知。抽象模板类：publicabstractclassAbstractPushTemplate{publicvoidpush(intcustomerId,StringshopName){System.out.println("Readytopush...");执行（客户编号，商店名称）；System.out.println("推送完成\n");}abstractprotectedvoidexecute(intcustomerId,StringshopName);}优惠券特定模板；publicclassPushCouponTemplateextendsAbstractPushTemplate{@Overrideprotectedvoidexecute(intcustomerId,StringshopName){System.out.println("Member:"+customerId+",你好,"+shopName+"送你一张优惠券");}}点具体模板；publicclassPushScoreTemplateextendsAbstractPushTemplate{@Overrideprotectedvoidexecute(intcustomerId,StringshopName){System.out.println("Member:"+customerId+",hello,"+shopName+"送你10分");}}使用示例：AbstractPushTemplatetemplate1=newPushCouponTemplate();template1.push(1,"糖果店");AbstractPushTemplatetemplate2=newPushScoreTemplate();template2.push(1,"服装店");显然，实现的模板越多，子类就越多。用java8重构后，以上3个模板（包括抽象类模板）可以减少为1个，参考如下：publicclassPushTemplateLambda{publicvoidpush(intcustomerId,StringshopName,Consumerexecute){.out.println("准备推送...");Object[]param=newObject[]{customerId,shopName};执行。接受（参数）；System.out.println("推送完成\n");}}借助Consumer函数接口，可以省略子类实现，具体实现在使用时决定，如：newPushTemplateLambda().push(1,"CandyStore",(Object[]obj)->{System.out.println("会员:"+obj[0]+",你好,"+obj[1]+"送你一张优惠券");});newPushTemplateLambda().push(1,"服装店",(Object[]obj)->{System.out.println("会员："+obj[0]+",你好,"+obj[1]+"送你10分");});3.观察者模式思路：基于一个主题主题，在主题上注册了一堆观察者。当事件发生时，Subject根据注册列表通知所有观察者。观察者接口：publicinterfaceObserver{voidnotify(StringorderNo);}Subject接口：publicinterfaceSubject{voidregisterObserver(Observero);voidnotifyAllObserver(StringorderNo);}Subject接口实现：publicclassSubjectImplimplementsSubject{privatefinalListlist=newArrayList<>();@OverridepublicvoidregisterObserver(Observero){list.add(o);}@OverridepublicvoidnotifyAllObserver(StringorderNo){list.forEach(c->c.notify(orderNo));}}观察者的两种实现方式：OrderObserver:publicclassOrderObserverimplementsObserver{@Overridepublicvoidnotify(StringorderNo){System.out.println("Order"+orderNo+"状态更新为【已付款】");}}股票观察者；publicclassStockObserverimplementsObserver{@Overridepublicvoidnotify(StringorderNo){System.out.println("Order"+orderNo+"仓库已通知发货！");}}测试一：staticvoidtest1(){Subjectsubject=newSubjectImpl();子ject.registerObserver(newOrderObserver());subject.registerObserver(newStockObserver());subject.notifyAllObserver("001");}用java8重构后接口可以提供默认的实现方法，我们新建一个subject接口；publicinterfaceNewSubject{Listlist=newArrayList<>();默认voidregisterObserver(Observero){list.add(o);}默认voidnofityAllObserver(StringorderNo){list.forEach(c->c.notify(orderNo));}}使用：staticvoidtest2(){NewSubjectsubject=newNewSubject(){};subject.registerObserver((StringorderNo)->System.out.println("Order"+orderNo+"状态更新为[Paid]"));subject.registerObserver((StringorderNo)->System.out.println("Order"+orderNo+"仓库已通知发货！"));subject.nofityAllObserver("002");}只用了2个接口来实现观察者模式4.责任链/责任链模式的核心思想：每个处理环节都有一个“指针”指向下一个处理器，类似于链表。处理器接口：publicinterfaceProcessor{ProcessorgetNextProcessor();voidprocess(Stringparam);}抽像实例：publicabstractclassAbstractProcessorimplementsProcessor{privateProcessornext;publicAbstractProcessor（处理器处理器）{this.next=processor;}@OverridepublicProcessorgetNextProcessor(){返回下一个；}@Overridepublicabstractvoidprocess(Stringparam);}定义2个具体的实现：publicclassProcessorImpl1extendsAbstractProcessor{publicProcessorImpl1(Processorprocessor){super(processor);}@Overridepublicvoidprocess(Stringparam){System.out.println("处理器1正在处理："+param);如果(getNextProcessor()!=null){getNextProcessor().process(param);}}}及；publicclassProcessorImpl2extendsAbstractProcessor{publicProcessorImpl2(Processornext){super(next);}@Overridepublicvoidprocess(Stringparam){System.out.println("处理器2正在处理："+param);如果(getNextProcessor()!=null){getNextProcessor().process(param);}}}使用示例：staticvoidtest1(){Processorp1=newProcessorImpl1(null);处理器p2=newProcessorImpl2(p1);p2.process("somethinghappened");}用java8重构后，只需要一个新的接口；@FunctionalInterfacepublicinterfaceNewProcessor{Consumerprocess(Stringparam);}同样的效果可以写的很简洁：staticvoidtest2(){Consumerp1=param->System.out.println("processor1is处理：“+参数）；Consumerp2=param->System.out.println("处理器2正在处理："+param);p2.andThen(p1).accept("somethinghappened");}andThen自然是另一种getNextProcessor表达重要提示：什么时候用lambda什么时候不用看情况。如果处理逻辑比较简单，可以使用lamdba进行重构，让代码更加简洁易读。如果处理逻辑复杂，你还是应该用“类”。
