《Head First 设计模式》学习笔记——模板方法模式

//声明为抽象类，子类必须实现其操作
public abstract class CaffeineBeverage
{

	//声明为final，不希望子类覆盖这种方法
	final void prepareRecipe()
	{
		boilWater();
		brew();
		pourInCup();
		addCondiments();
	}

	//声明为抽象类，子类必须实现其操作
	abstract void brew();
	abstract void addCondiments();

	void boilWater()
	{
		System.out.println("Boiling water");
	}

	void pourInCup()
	{
		System.out.println("Pouring into cup");
	}
}

//extends继承
public class Tea extends CaffeineBeverage {
	//须要定义抽象方法
	public void brew() {
		System.out.println("Steeping the tea");
	}
	public void addCondiments() {
		System.out.println("Adding Lemon");
	}
}

public abstract class CaffeineBeverageWithHook {
 
	void prepareRecipe() {
		boilWater();
		brew();
		pourInCup();
		if (customerWantsCondiments()) {
			addCondiments();
		}
	}
 
	abstract void brew();
 
	abstract void addCondiments();
 
	void boilWater() {
		System.out.println("Boiling water");
	}
 
	void pourInCup() {
		System.out.println("Pouring into cup");
	}
 
	//定义了一个缺省实现，子类能够覆盖它。但不见得一定要这么做
	boolean customerWantsCondiments() {
		return true;
	}
}

public class CoffeeWithHook extends CaffeineBeverageWithHook {
 
	public void brew() {
		System.out.println("Dripping Coffee through filter");
	}
 
	public void addCondiments() {
		System.out.println("Adding Sugar and Milk");
	}
 
	//覆盖了这种方法。提供了自己的功能
	public boolean customerWantsCondiments() {

		//让用户输入对调料的决定
		String answer = getUserInput();

		if (answer.toLowerCase().startsWith("y")) {
			return true;
		} else {
			return false;
		}
	}
 
	private String getUserInput() {
		String answer = null;

		System.out.print("Would you like milk and sugar with your coffee (y/n)? ");

		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		try {
			answer = in.readLine();
		} catch (IOException ioe) {
			System.err.println("IO error trying to read your answer");
		}
		if (answer == null) {
			return "no";
		}
		return answer;
	}
}