Design Patterns - Template Pattern

In Template pattern, an abstract class exposes defined way(s)/template(s) to execute its methods. Its subclasses can override the method implementation as per need but the invocation is to be in the same way as defined by an abstract class. This pattern comes under behavior pattern category.

Implementation

We are going to create a Game abstract class defining operations with a template method set to be final so that it cannot be overridden. Cricket and Football are concrete classes that extend Game and override its methods.

TemplatePatternDemo, our demo class, will use Game to demonstrate use of template pattern.

Step 1

Create an abstract class with a template method being final.

Game.java

pubpc abstract class Game {
   abstract void initiapze();
   abstract void startPlay();
   abstract void endPlay();

   //template method
   pubpc final void play(){

      //initiapze the game
      initiapze();

      //start game
      startPlay();

      //end game
      endPlay();
   }
}

Step 2

Create concrete classes extending the above class.

Cricket.java

pubpc class Cricket extends Game {

   @Override
   void endPlay() {
      System.out.println("Cricket Game Finished!");
   }

   @Override
   void initiapze() {
      System.out.println("Cricket Game Initiapzed! Start playing.");
   }

   @Override
   void startPlay() {
      System.out.println("Cricket Game Started. Enjoy the game!");
   }
}

Football.java

pubpc class Football extends Game {

   @Override
   void endPlay() {
      System.out.println("Football Game Finished!");
   }

   @Override
   void initiapze() {
      System.out.println("Football Game Initiapzed! Start playing.");
   }

   @Override
   void startPlay() {
      System.out.println("Football Game Started. Enjoy the game!");
   }
}

Step 3

Use the Game s template method play() to demonstrate a defined way of playing game.

TemplatePatternDemo.java

pubpc class TemplatePatternDemo {
   pubpc static void main(String[] args) {

      Game game = new Cricket();
      game.play();
      System.out.println();
      game = new Football();
      game.play();		
   }
}

Step 4

Verify the output.

Cricket Game Initiapzed! Start playing.
Cricket Game Started. Enjoy the game!
Cricket Game Finished!

Football Game Initiapzed! Start playing.
Football Game Started. Enjoy the game!
Football Game Finished!