面向对象应用（一）

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1 被客户不断变化的需求 “折磨” 第一次需求 class Printer{void Open(){System out printl

1.被客户不断变化的需求 “折磨”

 

第一次需求

          

class Printer{
    void Open(){
        System.out.println("Open");
    }
    
    void Close(){
        System.out.println("Close");
    }
    
    void Print(String s){
        System.out.println("Print--->" + s);
    }
}
1 class Test{
2     public static void main(String args []){
3         Printer printer = new Printer();
4         printer.Open();
5         printer.Print("abc");
6         printer.Close();
7     }
8 }

           

 

 

第二次需求

                                

 1 class HPPrinter{
 2     void Open(){
 3         System.out.println("Open");
 4     }
 5     
 6     void Close(){
 7         System.out.println("Close");
 8     }
 9     
10     void Print(String s){
11         System.out.println("Print--->" + s);
12     }
13 }
 1 class CannonPrinter{
 2     void Open(){
 3         System.out.println("Open");
 4     }
 5     
 6     void Close(){
 7         this.Clean();
 8         System.out.println("Close");
 9     }
10     
11     void Print(String s){
12         System.out.println("Print--->" + s);
13     }
14     
15     void Clean(){
16         System.out.println("Clean");
17     }
18 }
 1 class Test{
 2     public static void main(String args []){
 3         int flag = 0;
 4         
 5         if( flag == 0){
 6             HPPrinter hpprinter = new HPPrinter();
 7             hpprinter.Open();
 8             hpprinter.Print("abc");
 9             hpprinter.Close();
10         }
11         else if( flag == 1){
12             CannonPrinter cannonprinter = new CannonPrinter();
13             cannonprinter.Open();
14             cannonprinter.Print("abc");
15             cannonprinter.Close();
16         }
17     }
18 }

             

              

第二次需求优化（消除重复代码）          

 1 class Printer{
 2     void Open(){
 3         System.out.println("Open");
 4     }
 5     
 6     void Close(){
 7         System.out.println("Close");
 8     }
 9     
10     void Print(String s){
11         System.out.println("Print--->" + s);
12     }
13 }

 

 1 class HPPrinter extends Printer{2 }

 1 class CannonPrinter extends Printer{
 2     void Close(){
 3         this.Clean();
 4         super.Close();
 5     }
 6         
 7     void Clean(){
 8         System.out.println("Clean");
 9     }
10 }
 1 class Test{
 2     public static void main(String args []){
 3         int flag = 1;
 4         
 5         if( flag == 0){
 6             HPPrinter hpprinter = new HPPrinter();
 7             hpprinter.Open();
 8             hpprinter.Print("abc");
 9             hpprinter.Close();
10         }
11         else if( flag == 1){
12             CannonPrinter cannonprinter = new CannonPrinter();
13             cannonprinter.Open();
14             cannonprinter.Print("123");
15             cannonprinter.Close();
16         }
17     }
18 }