23种创新模式总署
父文链接

起因：

为了解决类与类之家的依赖关系,降低类类之间的耦合度

代码：
类类

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!");  
    }  
} 

外观

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：

类类(cpu等。。)间的联系是通过外观者(computer)联系协调的，他们之间没直接联系，各自只需要处理好各自的工作即可。