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模板方法模式:UML類圖

模板方法模型是一種行為設計模型。模板方法是一個定義在父類別的方法,在模板方法中會呼叫多個定義在父類別的其他方法,而這些方法有可能只是抽象方法並沒有實作,模板方法僅決定這些抽象方法的執行順序,這些抽象方法的實作由子類別負責,並且子類別不允許覆寫模板方法。

用法编辑

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)编辑

 /**
  * 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
     }
 }