23种设计模式之外观模式代码实例

外观模式是为了解决类与类之家的依赖关系的，

如IOC一样，把存在很多依赖关系的类放在一起统一管理，

就像一个电脑里面有很多零件，但是用电脑的人只能看到机箱。

    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!");  
        }  
    }  

    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!");  
        }  
    }  

测试类：

    public class User {  
      
        public static void main(String[] args) {  
            Computer computer = new Computer();  
            computer.startup();  
            computer.shutdown();  
        }  
    }  

输出：

start the computer!
cpu startup!
memory startup!
disk startup!
start computer finished!
begin to close the computer!
cpu shutdown!
memory shutdown!
disk shutdown!
computer closed!