CS-Notes/notes/设计模式 - 模板方法.md

# 模板方法（Template Method）

## Intent

定义算法框架，并将一些步骤的实现延迟到子类。

通过模板方法，子类可以重新定义算法的某些步骤，而不用改变算法的结构。

## Class Diagram

![](https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/ac6a794b-68c0-486c-902f-8d988eee5766.png)\


## Implementation

冲咖啡和冲茶都有类似的流程，但是某些步骤会有点不一样，要求复用那些相同步骤的代码。

![](https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/11236498-1417-46ce-a1b0-e10054256955.png)\


```java
public abstract class CaffeineBeverage {

    final void prepareRecipe() {
        boilWater();
        brew();
        pourInCup();
        addCondiments();
    }

    abstract void brew();

    abstract void addCondiments();

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

    void pourInCup() {
        System.out.println("pourInCup");
    }
}
```

```java
public class Coffee extends CaffeineBeverage {
    @Override
    void brew() {
        System.out.println("Coffee.brew");
    }

    @Override
    void addCondiments() {
        System.out.println("Coffee.addCondiments");
    }
}
```

```java
public class Tea extends CaffeineBeverage {
    @Override
    void brew() {
        System.out.println("Tea.brew");
    }

    @Override
    void addCondiments() {
        System.out.println("Tea.addCondiments");
    }
}
```

```java
public class Client {
    public static void main(String[] args) {
        CaffeineBeverage caffeineBeverage = new Coffee();
        caffeineBeverage.prepareRecipe();
        System.out.println("-----------");
        caffeineBeverage = new Tea();
        caffeineBeverage.prepareRecipe();
    }
}
```

```html
boilWater
Coffee.brew
pourInCup
Coffee.addCondiments
-----------
boilWater
Tea.brew
pourInCup
Tea.addCondiments
```

## JDK

* java.util.Collections#sort()
* java.io.InputStream#skip()
* java.io.InputStream#read()
* java.util.AbstractList#indexOf()