62 lines
1.4 KiB
Java
62 lines
1.4 KiB
Java
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## 外观（Facade）
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### Intent
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提供了一个统一的接口，用来访问子系统中的一群接口，从而让子系统更容易使用。
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### Class Diagram
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<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/f9978fa6-9f49-4a0f-8540-02d269ac448f.png"/> </div><br>
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### Implementation
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观看电影需要操作很多电器，使用外观模式实现一键看电影功能。
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```java
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public class SubSystem {
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public void turnOnTV() {
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System.out.println("turnOnTV()");
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}
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public void setCD(String cd) {
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System.out.println("setCD( " + cd + " )");
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}
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public void startWatching(){
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System.out.println("startWatching()");
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}
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}
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```
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```java
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public class Facade {
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private SubSystem subSystem = new SubSystem();
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public void watchMovie() {
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subSystem.turnOnTV();
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subSystem.setCD("a movie");
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subSystem.startWatching();
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}
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}
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```
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```java
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public class Client {
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public static void main(String[] args) {
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Facade facade = new Facade();
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facade.watchMovie();
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}
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}
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```
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### 设计原则
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最少知识原则：只和你的密友谈话。也就是说客户对象所需要交互的对象应当尽可能少。
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<div align="center"><img width="320px" src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/githubio/公众号二维码-2.png"></img></div>
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