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：

package templmethod;

abstract class Audi {
    
    protected boolean isWhistle;
    
    protected void start(){
        System.out.println("starting....");
    }
    
    protected void stop(){
        System.out.println("stopped....");
    }
    
    protected abstract void driveNormal();
    
    protected abstract void driveSlowly();
    
    protected void reverse(){
        setWhistle();
        if(isWhistle){
            System.out.println("倒车请注意...倒车请注意...");
            System.out.println("backing now....");
        }else{
            System.out.println("backing now....");
        }
    }
    
    public void setWhistle(){
        this.isWhistle = true;
    }
        
    
}

package templmethod;

public class AudiA4 extends Audi{

    @Override
    public void driveNormal() {
        System.out.println("A4 high-end driving normally....");
    }

    @Override
    public void driveSlowly() {
        System.out.println("A4 high-end driving slowly....");
    }
    
    @Override
    public void setWhistle() {
        isWhistle =  false;
    }


}

package templmethod;

public class AudiC5 extends Audi {

    @Override
    public void driveNormal() {
        System.out.println("C5 stdeady driving normally....");
    }

    @Override
    public void driveSlowly() {
        System.out.println("C5 stdeady driving slowly....");
    }
    
    @Override
    public void setWhistle() {
        isWhistle = true;
    }

}

package templmethod;

public class Driver {
    private Audi myCar;
    
    /*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;
     * 但是每一步是可以通过子类的延迟实现，来定义的
     */
    public void driveCar(){
        myCar.start();
        myCar.driveNormal();
        System.out.println("GPS提示：前方90度急转弯....");
        myCar.driveSlowly();
        System.out.println("GPS提示：前方无路可走....");
        myCar.reverse();
    }
    
    public void stopCar(){
        myCar.stop();
    }
    
    public void buyCar(Audi audi){
        this.myCar = audi;
    }
}

package templmethod;

public class Client {
    public static void main(String[] args) {
        Driver driver = new Driver();
        driver.buyCar(new AudiA4());
        driver.driveCar();
        
        System.out.println("--------------------------------------");
        
        driver.buyCar(new AudiC5());
        driver.driveCar();
        
    }
}

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....