《JAVA编程思想》学习备忘（第155页：Initialization & Cleanup）--2

 

The this keyword

The this keyword-which can be used only inside a non-static method-produces the reference to the object that the method has been called for.

但调用同处一类中的方法时不需要this 。

The this keyword is used only for those special cases in which you need to explicitly use the reference to the current object.

举例：

public class Leaf{

    int i = 0;

    Leaf increment(){

        i++;

        return this;

    }

    void print(){

        System.out.println("i = " + i);

    }

    public static void main(String[] args){

        Leaf x = new Leaf();

        x.increment().increment().increment().print();

    }

}

输出结果：i = 3;

 

The this keyword is also useful for passing the current object to another method:

class Person{

    public void eat(Apple apple){

        Apple peeled = apple.getPeeled();

        System.out.println("Yummy");

    }

}

class Peeler{

    static Apple peel(Apple apple){

        return apple;

    }

}

class Apple{

    Apple getPeeled(){

        return Peeler.peel(this);

    }

}

public class PassingThis{

    public static void main(String[] args){

        new Person().eat(new Apple());

    }

}

输出：Yummy

main方法中首先“新摘一个苹果”：new Apple(),然后“将苹果拿去削皮”：Peeler.peel(this)，接下来将“削了皮的苹果”送进了“人嘴里”。

 

（待续）