起因：
為了解決類與類之家的依賴關系,降低類類之間的耦合度
代碼：
類類
public class CPU {
public void startup(){
System.out.println("cpu startup!");
}
public void shutdown(){
System.out.println("cpu shutdown!");
}
}
public class Memory {
public void startup(){
System.out.println("memory startup!");
}
public void shutdown(){
System.out.println("memory shutdown!");
}
}
public class Disk {
public void startup(){
System.out.println("disk startup!");
}
public void shutdown(){
System.out.println("disk shutdown!");
}
}
外觀
public class Computer {
private CPU cpu;
private Memory memory;
private Disk disk;
public Computer(){
cpu = new CPU();
memory = new Memory();
disk = new Disk();
}
public void startup(){
System.out.println("start the computer!");
cpu.startup();
memory.startup();
disk.startup();
System.out.println("start computer finished!");
}
public void shutdown(){
System.out.println("begin to close the computer!");
cpu.shutdown();
memory.shutdown();
disk.shutdown();
System.out.println("computer closed!");
}
}
使用
public class User {
public static void main(String[] args) {
Computer computer = new Computer();
computer.startup();
computer.shutdown();
}
}
想法：
類類(cpu等。。)間的聯系是通過外觀者(computer)聯系協調的，他們之間沒直接聯系，各自只需要處理好各自的工作即可。
