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依赖倒转原则是指:
1)高层模块不应依赖低层模块,二者都应该依赖其抽象 2)抽象不应该依赖细节,细节应该依赖抽象 3)依赖倒转(置)的中心思想是面向 接口 编程 4)依赖倒转原则是基本这样的设计理念:相对于细节的多变性,抽象的东西要稳定的多,以抽象为基础搭建的架构比以细节为基础搭建的架构要稳定的多。在Java中,抽象指的是接口或抽象类,细节就是具体的实现类 5)使用接口或抽象类的目的是制定好规范,而不涉及任何具体的操作,把展现细节的任务交给它们的实现类去完成定义一个Person类用于接收邮件、微信等的消息
public class DependecyInversion { public static void main(String[] args) { Person person = new Person(); person.receive(new Email()); }}class Email{ public String getInfo(){ return "电子邮件信息:hello,world"; }}// 完成Person接收消息的功能// 方式1 分析// 1. 简单,比较容易想到// 2. 如果我们获取的对象是 微信、短信等等,则新增类,同时Person也要增加相应的接收方法// 3. 解决思路:引入一个抽象的接口IReceiver,表示接收者,这样Person类与接口IReceiver发生依赖// 因为Email、WeiXin等属于接收的范围,她们各自实现IReceiver接口就可以,这样符合依赖倒转原则class Person { public void receive(Email email){ System.out.println(email.getInfo()); }}
public class DependecyInversion { public static void main(String[] args) { //客户端无需改变 Person person = new Person(); person.receive(new Email()); person.receive(new WeiXin()); }}//定义接口interface IReceiver{ public String getInfo();}class Email implements IReceiver{ public String getInfo(){ return "电子邮件信息:hello,world"; }}class WeiXin implements IReceiver{ public String getInfo(){ return "微信信息:hello,ok"; }}//方式2class Person { //这里我们是对接口进行依赖 public void receive(IReceiver receiver){ System.out.println(receiver.getInfo()); }}
1)接口传递
2)构造方法传递 3)setter方式传递接口传递案例:
public class DependecyInversion { public static void main(String[] args) { //方式1 ChangHong changHong = new ChangHong(); OpenAndClose openAndClose = new OpenAndClose(); openAndClose.open(changHong); }}//方式1:通过接口传递,实现依赖//开关的接口interface IOpenAndClose{ public void open(ITV tv); //抽象方法,接收接口}//ITV接口interface ITV{ public void play();}class ChangHong implements ITV{ @Override public void play() { System.out.println("长虹电视机,打开"); }}//实现接口class OpenAndClose implements IOpenAndClose{ public void open(ITV tv){ tv.play(); }}
构造方法传递案例:
public class DependecyInversion { public static void main(String[] args) { //方式2 OpenAndClose openAndClose = new OpenAndClose(changHong); openAndClose.open(); }}class ChangHong implements ITV{ @Override public void play() { System.out.println("长虹电视机,打开"); }}//方式2:通过构造方法,实现依赖传递interface IOpenAndClose{ public void open(); //抽象方法,接收接口}//ITV接口interface ITV{ //ITV接口 public void play();}class OpenAndClose implements IOpenAndClose{ public ITV tv; //成员 public OpenAndClose(ITV tv){ //构造器 this.tv = tv; } public void open(){ this.tv.play(); }}
setter方式传递案例:
public class DependecyInversion { public static void main(String[] args) { //方式3 OpenAndClose openAndClose = new OpenAndClose(); openAndClose.setTv(changHong); openAndClose.open(); }}class ChangHong implements ITV{ @Override public void play() { System.out.println("长虹电视机,打开"); }}//方式3:通过setter方法传递interface IOpenAndClose{ public void open(); //抽象方法,接收接口 public void setTv(ITV tv);}interface ITV{ //ITV接口 public void play();}class OpenAndClose implements IOpenAndClose{ public ITV tv; //成员 public void setTv(ITV tv){ this.tv = tv; } public void open(){ this.tv.play(); }}
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