【设计模式】工厂&工厂方法&模板方法

工厂：根据不同条件返回不同类型的对象。

工厂方法：通过子类复写父类的(抽象)方法，返回具体对象。

模板方法：定义通用的程序执行流程，某些不确定的步骤在父类中使用抽象方法进行定义，具体实现交给子类。

package pattern.factorymethod;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ThreadLocalRandom;

/**
 * 工厂
 * 工厂方法
 * 模板方法
 */
public class FactoryMethod {
	public static void main(String[] args) {
		Game game = GameFactory.createGame("Game");
		game.start();
		
		System.out.println("===================================");
		
		Game magicGame = GameFactory.createGame("MagicGame");
		magicGame.start();
	}
	
}

/**
 * 工厂 - Factory
 * 负责创建对象 
 */
class GameFactory {
	public static Game createGame(String gameType) {
		Game game = null;
		
		if(gameType==null) {
			throw new IllegalArgumentException("Game can't be null");
		}
		
		if(gameType.startsWith("Game")) {
			game = new Game();
		}
		
		if(gameType.startsWith("MagicGame")) {
			game = new MagicGame();
		}
		
		return game;
	}
}

class Game {
	private Set<Room> rooms = new HashSet<Room>(); 
	
	public Game() {
		init();
	}
	
	/**
	 * 模板方法
	 * 	通用的流程可以使用模板方法进行定制
	 * 	还可以设置一个钩子，由子类决定哪些步骤是需要的
	 */
	private void init() {
		Room room1 = MakeRoom();
		Room room2 = MakeRoom();
		room1.connect(room2);
		addRoom(room1).addRoom(room2);
	}
	
	private Game addRoom(Room room) {
		rooms.add(room);
		return this;
	}
	
	/**
	 * 工厂方法-Factory Method
	 * 返回一个默认的子类对象。
	 * 另一种常见做法是将其定义为抽象方法。
	 */
	protected Room MakeRoom() {
		return new OrdinaryRoom("OrdinaryRoom"+ThreadLocalRandom.current().nextInt());
	}
	
	public void start() {
		System.out.println("Game start: " + Arrays.toString(rooms.toArray()));
	}
}

abstract class Room {
	String name;
	int capacity = 100;
	abstract void connect(Room otherRoom);
}

class OrdinaryRoom extends Room {
	
	public OrdinaryRoom(String name) {
		super.name = name;
	}
	
	public void connect(Room otherRoom) {
		System.out.println(this.name + " connect to " + otherRoom.name);
	}
	
}

class MagicRoom extends Room {
	public MagicRoom(String name) {
		super.name = name;
		super.capacity = 200;
	}
	public void connect(Room otherRoom) {
		System.out.println(this.name + " connect to " + otherRoom.name);
		System.out.println("Players can see each other with network camera");
	}
	
}

class MagicGame extends Game {

	@Override
	protected Room MakeRoom() {
		return new MagicRoom("MagicRoom"+ThreadLocalRandom.current().nextInt(10));
	}

}