模板方法模式

定义一个方法，安排算法的步骤，算法每一步的详细实现策略可以延迟到子类执行。

可以在算法里定义hook，让客户选择性的改变算法的策略，而不需要本身算法的步骤。

代码示例：

 1 package templmethod;
 2 
 3 abstract class Audi {
 4     
 5     protected boolean isWhistle;
 6     
 7     protected void start(){
 8         System.out.println("starting....");
 9     }
10     
11     protected void stop(){
12         System.out.println("stopped....");
13     }
14     
15     protected abstract void driveNormal();
16     
17     protected abstract void driveSlowly();
18     
19     protected void reverse(){
20         setWhistle();
21         if(isWhistle){
22             System.out.println("倒车请注意...倒车请注意...");
23             System.out.println("backing now....");
24         }else{
25             System.out.println("backing now....");
26         }
27     }
28     
29     public void setWhistle(){
30         this.isWhistle = true;
31     }
32         
33     
34 }

View Code

 1 package templmethod;
 2 
 3 public class AudiA4 extends Audi{
 4 
 5     @Override
 6     public void driveNormal() {
 7         System.out.println("A4 high-end driving normally....");
 8     }
 9 
10     @Override
11     public void driveSlowly() {
12         System.out.println("A4 high-end driving slowly....");
13     }
14     
15     @Override
16     public void setWhistle() {
17         isWhistle =  false;
18     }
19 
20 
21 }

View Code

 1 package templmethod;
 2 
 3 public class AudiC5 extends Audi {
 4 
 5     @Override
 6     public void driveNormal() {
 7         System.out.println("C5 stdeady driving normally....");
 8     }
 9 
10     @Override
11     public void driveSlowly() {
12         System.out.println("C5 stdeady driving slowly....");
13     }
14     
15     @Override
16     public void setWhistle() {
17         isWhistle = true;
18     }
19 
20 }

View Code

 1 package templmethod;
 2 
 3 public class Driver {
 4     private Audi myCar;
 5     
 6     /*传说中的定义算法的方法，具体的步骤由它规定，任何人都不可以改变;
 7      * 但是每一步是可以通过子类的延迟实现，来定义的
 8      */
 9     public void driveCar(){
10         myCar.start();
11         myCar.driveNormal();
12         System.out.println("GPS提示：前方90度急转弯....");
13         myCar.driveSlowly();
14         System.out.println("GPS提示：前方无路可走....");
15         myCar.reverse();
16     }
17     
18     public void stopCar(){
19         myCar.stop();
20     }
21     
22     public void buyCar(Audi audi){
23         this.myCar = audi;
24     }
25 }

View Code

 1 package templmethod;
 2 
 3 public class Client {
 4     public static void main(String[] args) {
 5         Driver driver = new Driver();
 6         driver.buyCar(new AudiA4());
 7         driver.driveCar();
 8         
 9         System.out.println("--------------------------------------");
10         
11         driver.buyCar(new AudiC5());
12         driver.driveCar();
13         
14     }
15 }

View Code

输出结果：

starting....
A4 high-end driving normally....
GPS提示：前方90度急转弯....
A4 high-end driving slowly....
GPS提示：前方无路可走....
backing now....
--------------------------------------
starting....
C5 stdeady driving normally....
GPS提示：前方90度急转弯....
C5 stdeady driving slowly....
GPS提示：前方无路可走....
倒车请注意...倒车请注意...
backing now....