模板模式（ Template Pattern）

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2023-12-01

在模板模式中，抽象类公开定义的方式/模板以执行其方法。它的子类可以根据需要覆盖方法实现，但调用的方式与抽象类的定义相同。此模式属于行为模式类别。

实现 (Implementation)

我们将创建一个Game抽象类，定义操作，模板方法设置为final，以便不能覆盖它。 Cricket和Football是扩展Game并覆盖其方法的具体类。

我们的演示类TemplatePatternDemo将使用Game来演示模板模式的使用。

Step 1

使用最终的模板方法创建一个抽象类。

Game.java

public abstract class Game {
   abstract void initialize();
   abstract void startPlay();
   abstract void endPlay();
   //template method
   public final void play(){
      //initialize the game
      initialize();
      //start game
      startPlay();
      //end game
      endPlay();
   }
}

Step 2

创建扩展上述类的具体类。

Cricket.java

public class Cricket extends Game {
   @Override
   void endPlay() {
      System.out.println("Cricket Game Finished!");
   }
   @Override
   void initialize() {
      System.out.println("Cricket Game Initialized! Start playing.");
   }
   @Override
   void startPlay() {
      System.out.println("Cricket Game Started. Enjoy the game!");
   }
}

Football.java

public class Football extends Game {
   @Override
   void endPlay() {
      System.out.println("Football Game Finished!");
   }
   @Override
   void initialize() {
      System.out.println("Football Game Initialized! Start playing.");
   }
   @Override
   void startPlay() {
      System.out.println("Football Game Started. Enjoy the game!");
   }
}

Step 3

使用Game的模板方法play（）来演示一种定义的游戏方式。

TemplatePatternDemo.java

public class TemplatePatternDemo {
   public static void main(String[] args) {
      Game game = new Cricket();
      game.play();
      System.out.println();
      game = new Football();
      game.play();		
   }
}

Step 4

验证输出。

Cricket Game Initialized! Start playing.
Cricket Game Started. Enjoy the game!
Cricket Game Finished!
Football Game Initialized! Start playing.
Football Game Started. Enjoy the game!
Football Game Finished!