门面模式 facade

门面模式 实现了子模块 与客户端 之间的松耦合 关系，从而屏蔽了 子模块内部实现的细节，只是将客户端需要的 接口提供给客户，使得子模块的组件如果发生变化不会影响客户端的使用，“松耦合，高内聚” 的体现。

一个薪水结算的例子

1 public class Salary {
2   public double getSalary(String empno){
3       return 200;
4   }
5
6 }

1 public class Holiday {
2    public double getHoliday(String empno){
3        return 2;
4    }
5 }

1 public class Tax {
2    public double getTax(String empno){
3        return 0;
4    }
5 }

1 public interface Computer {
2   public double doSalary(String empno);
3 }

 1 public class ComputerSalary implements Computer {
 2
 3     @Override
 4     public double doSalary(String empno) {
 5         Salary salary = new Salary();
 6         Holiday holiday = new Holiday();
 7         Tax tax = new Tax();
 8         Double money = salary.getSalary(empno) * (30  - holiday.getHoliday(empno))-tax.getTax(empno);
 9         return money;
10     }
11
12 }

 1 import java.io.IOException;
 2 import java.io.InputStream;
 3 import java.util.Properties;
 4
 5 public class PropertiesUtil {
 6     public static Object getInstance() {
 7         Object obj = null;
 8         try {
 9             Properties p = new Properties();
10             InputStream in = null;
11             in = Client.class.getResourceAsStream("class.properties");
12             try {
13                 p.load(in);
14             } catch (IOException e) {
15
16                 e.printStackTrace();
17             } finally {
18                 try {
19                     in.close();
20                 } catch (IOException e) {
21
22                     e.printStackTrace();
23                 }
24             }
25
26             obj = (Object) Class.forName(p.getProperty("class")).newInstance();
27         } catch (InstantiationException e) {
28
29             e.printStackTrace();
30         } catch (IllegalAccessException e) {
31
32             e.printStackTrace();
33         } catch (ClassNotFoundException e) {
34
35             e.printStackTrace();
36         }
37         return obj;
38     }
39
40
41
42 }

1 public class Client {
2     public static void main(String[] args) {
3         Computer computer = (Computer) PropertiesUtil.getInstance();
4         System.out.println(computer.doSalary("1994"));// 调用实现类方法
5     }
6
7 }

包下的 配置文件 class.properties

class = com.facade.ComputerSalary