模板方法

模板方法模式：UML類圖

模板方法模式定義了一個演算法的步驟，並允許次類別為一個或多個步驟提供其實踐方式。讓次類別在不改變演算法架構的情況下，重新定義演算法中的某些步驟。在軟件工程中，它是一種軟件設計模式，和C++模板没有關連。

用法

模板方法模式多用在：

• 某些類別的演算法中，實做了相同的方法，造成程式碼的重複。
• 控制子類別必須遵守的一些事項。
• ...

用例（Java）

 /**
  * An abstract class that is common to several games in
  * which players play against the others, but only one is
  * playing at a given time.
  */
 
 abstract class Game {
 
     private int playersCount;
 
     abstract void initializeGame();
 
     abstract void makePlay(int player);
 
     abstract boolean endOfGame();
 
     abstract void printWinner();
 
     /* A template method : */
     final void playOneGame(int playersCount) {
         this.playersCount = playersCount;
         initializeGame();
         int j = 0;
         while (!endOfGame()){
             makePlay(j);
             j = (j + 1) % playersCount;
         }
         printWinner();
     }
 }
 
//Now we can extend this class in order to implement actual games:
 
 class Monopoly extends Game {
 
     /* Implementation of necessary concrete methods */
 
     void initializeGame() {
         // ...
     }
 
     void makePlay(int player) {
         // ...
     }
 
     boolean endOfGame() {
         // ...
     }
 
     void printWinner() {
         // ...
     }
 
     /* Specific declarations for the Monopoly game. */
 
     // ...
 
 }
 
 class Chess extends Game {
 
     /* Implementation of necessary concrete methods */
 
     void initializeGame() {
         // ...
     }
 
     void makePlay(int player) {
         // ...
     }
 
     boolean endOfGame() {
         // ...
     }
 
     void printWinner() {
         // ...
     }
 
     /* Specific declarations for the chess game. */
 
     // ...
 
 }

public class Player {

   public static void main(String[] args) {
       Game chessGame = new Chess();
       chessGame.initializeGame();
       chessGame.playOneGame(1); //call template method
   }

}