不止Coding
2017-08-01 01:10
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Java 中子类继承父类,打印输出奇怪的问题?求解释!

 package com.demo;

class Plate {
    Plate(int i) {
        System.out.println("Plate constructor");
    }
}

class DinnerPlate extends Plate {
    DinnerPlate(int i) {
        super(i);
        System.out.println("DinnerPlate constructor");
    }
}

class Utensil {
    Utensil(int i) {
        System.out.println("Utensil constructor");
    }
}

class Spoon extends Utensil {
    Spoon(int i) {
        super(i);
        System.out.println("Spoon constructor");
    }
}

class Fork extends Utensil {
    Fork(int i) {
        super(i);
        System.out.println("Fork constructor");
    }
}

class Knife extends Utensil {
    Knife(int i) {
        super(i);
        System.out.println("Knife constructor");
    }
}

// A cultural way of doing something:
class Custom {
    Custom(int i) {
        System.out.println("Custom constructor");
    }
}

public class PlaceSetting extends Custom {
    Spoon sp;
    Fork frk;
    Knife kn;
    DinnerPlate pl;

    PlaceSetting(int i) {
        super(i + 1);
        sp = new Spoon(i + 2);
        frk = new Fork(i + 3);
        kn = new Knife(i + 4);
        pl = new DinnerPlate(i + 5);
        System.out.println("PlaceSetting constructor");
    }

    public static void main(String[] args) {
        PlaceSetting x = new PlaceSetting(9);
    }
}
//尽管编译器会强迫我们对基础类进行初始化,并要求我们在构建器最开头做这一工作,但它并不会监视我们是否正确初始化了成员对象。

最终打印输出
Spoon constructor
Utensil constructor
Fork constructor
Utensil constructor
Knife constructor
Plate constructor
DinnerPlate constructor
PlaceSetting constructor

console

为什么会输出plate,而非Utensil??????????

4条回答 默认 最新

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