模板方法
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。
模板方法模式：UML類圖
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
}
}
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