http://www.verejava.com/?id=16992848300456

/**
    题目: (孩子,学生) 吃 水果(苹果,葡萄,芒果,菠萝)

    思路：
        1. 抽象出类 : {孩子(Baby),学生(Student)}, 水果(Fruit){苹果(Apple),葡萄(Grape),芒果(Mango)}
        2. 找出类的关系: 
            水果 -> (孩子,学生)
            (苹果,葡萄,芒果) 是 水果的分类

        3. 找出属性: 孩子,学生(姓名,水果引用)  
        4. 找出方法: 孩子,学生都吃(eat)水果

    子类->父类的转换 作用 ：解耦 也就是降低类与类之间的耦合度 提供可扩展性
*/
public class Polymorphism4 {
    
    public static void main(String[] args) {
        //实例化一个Baby
        Baby baby = new Baby("李明");
        //实例化一个学生
        Student stu = new Student("张涛");

        //实例化一个苹果 和 一个葡萄
        Apple apple = new Apple("红富士");
        Grape grape = new Grape("黑葡萄");
        Mango mango = new Mango("大芒果");
        PineApple pineApple = new PineApple("菠萝");

        //李明吃水果
        baby.eat(apple);
        System.out.println(baby.getName() + " 吃了 " + baby.getFruit().getName());
        baby.eat(grape);
        System.out.println(baby.getName() + " 吃了 " + baby.getFruit().getName());
        baby.eat(mango);
        System.out.println(baby.getName() + " 吃了 " + baby.getFruit().getName());
        baby.eat(pineApple);
        System.out.println(baby.getName() + " 吃了 " + baby.getFruit().getName());

        //张涛吃水果
        stu.eat(apple);
        System.out.println(stu.getName() + " 吃了 " + stu.getFruit().getName());
        stu.eat(grape);
        System.out.println(stu.getName() + " 吃了 " + stu.getFruit().getName());
        stu.eat(mango);
        System.out.println(stu.getName() + " 吃了 " + stu.getFruit().getName());
        stu.eat(pineApple);
        System.out.println(stu.getName() + " 吃了 " + stu.getFruit().getName());

    }
}


class Baby {
    
    private Fruit fruit;
    private String name;

    public Baby(String name) {
        this.name = name;
    }

    public String getName() {
        return this.name;
    }

    public Fruit getFruit() {
        return this.fruit;
    }

    //吃水果
    public void eat(Fruit fruit) {
        this.fruit = fruit;
    }

}

class Student {
    
    private Fruit fruit;
    private String name;

    public Student(String name) {
        this.name = name;
    }

    public String getName() {
        return this.name;
    }

    public Fruit getFruit() {
        return this.fruit;
    }

    //吃水果
    public void eat(Fruit fruit) {
        this.fruit = fruit;
    }

}

class Fruit {
    
    private String name;

    public Fruit(String name) {
        this.name = name;
    }

    public String getName() {
        return this.name;
    }
}

class PineApple extends Fruit {
    
    public PineApple(String name) {
        super(name);
    }
}

class Apple extends Fruit {
    
    public Apple(String name) {
        super(name);
    }
}

class Grape extends Fruit {
    
    public Grape(String name) {
        super(name);
    }
}

class Mango extends Fruit {
    
    public Mango(String name) {
        super(name);
    }
}

http://www.verejava.com/?id=16992848300456