标签：作用 public 耦合度 tin static out close cad .sh
外观模式是为了解决类与类之间依赖关系的，外观模式将类间关系放在一个Facade类中，降低了类类之间的耦合度，该模式中不涉及接口
举一个经典的例子：
CPU类：
1 public class CPU { 2 public void startup(){ 3 System.out.println("cpu startup"); 4 } 5 6 public void shutdown(){ 7 System.out.println("cpu shutdown"); 8 } 9 }
Mainboard类：
1 public class Mainboard { 2 3 public void startup(){ 4 System.out.println("mainboard startup"); 5 } 6 7 public void shutdown(){ 8 System.out.println("mainboard shutdown"); 9 } 10 }
Disk类：
1 public class Disk { 2 3 public void startup(){ 4 System.out.println("disk startup"); 5 } 6 7 public void shutdown(){ 8 System.out.println("disk shutdown"); 9 } 10 }
Computer类（外观类）：
1 public class Computer { 2 private CPU cpu; 3 private Mainboard mainboard; 4 private Disk disk; 5 6 public Computer(){ 7 cpu = new CPU(); 8 mainboard = new Mainboard(); 9 disk = new Disk(); 10 } 11 12 public void startup(){ 13 System.out.println("starting the computer"); 14 cpu.startup(); 15 mainboard.startup(); 16 disk.startup(); 17 System.out.println("computer is started"); 18 } 19 20 public void shutdown(){ 21 System.out.println("closing the computer"); 22 disk.shutdown(); 23 mainboard.shutdown(); 24 cpu.shutdown(); 25 System.out.println("computer is closed"); 26 } 27 }
测试类：
1 public class Main { 2 3 public static void main(String[] args) { 4 Computer computer = new Computer(); 5 computer.startup(); 6 computer.shutdown(); 7 } 8 }
测试结果：
starting the computer cpu startup mainboard startup disk startup computer is started closing the computer disk shutdown mainboard shutdown cpu shutdown computer is closed
如果我们没有外观类（Computer），CPU、Mainboard、Disk之间将会相互持有实例对象，造成严重的依赖；而有了Computer，他们之间的关系被放在了Computer类里，这样就起到了解耦的作用。这就是外观模式！
标签：作用 public 耦合度 tin static out close cad .sh
原文地址：http://www.cnblogs.com/joshua-aw/p/6033987.html
