继承类(Java)，显式构造函数错误消息 [英] Inheritance classes (Java), explicit constructor error message

问题描述

所以我试图学习继承类.

so I am trying to learn about inheritance classes.

首先，我创建了一个名为Box的类来计算盒子的面积.

First I created a class called Box to calculate the area of the box.

然后，我创建了一个TestBox类，在其中创建了一个名为fedEx的框对象.

Then I created a TestBox Class in which I have created a box object called fedEx.

包装盒类:

public class Box {
    private String boxName;

    public void calculateArea(int length, int width) {
        System.out.println("Area of " + getBoxInfo() + (length * width));
    }

    public Box(String boxName) {
        this.boxName = boxName;
    }

    public String getBoxInfo() {
        return boxName;
    }
}

TestBox类:

public class TestBox {

    public static void main(String[] args) {

        Box fedEx = new Box("fedEx");
        fedEx.calculateArea(23, 2);
    }
}

到目前为止，如果我运行此代码，一切正常，并且打印屏幕显示Fedex 46的面积

So Far if I run this code everything works out fine and my print screen shows Area of Fedex 46

所以现在我去创建一个名为NewBox的新类，并使用扩展"继承Box类中的方法，该类用于计算Volume

So now I went to create a new class called NewBox and used "extends" to inherit the methods from the class Box, this class is used to calculate Volume

NewBox类:

public class NewBox extends Box {

    public void calculateVolume(int length, int width, int height) {
        System.out.println("Volume = " + (length * width * height));
    }
}

现在要进行测试，我在TestBox类中创建了一个称为UPS的新对象，现在我的TestBox类如下所示:

Now to test this I created a new object in my TestBox class called UPS, now my TestBox class looks like this:

public class TestBox {

    public static void main(String[] args) {

        Box fedEx = new Box("fedEx");
        fedEx.calculateArea(23, 2);

        NewBox UPS = new NewBox("UPS");
        UPS.calculateArea(3, 2);
        UPS.calculateVolume(3, 2, 2);
    }
}

当我尝试运行该程序时，出现以下错误消息:

When I try to run this program I get the following error message:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    The constructor NewBox(String) is undefined
    at day3.inheritence.TestBox.main(TestBox.java:10)

我正在使用eclipse作为我的IDE.

I am using eclipse as my IDE.

我该如何解决我的代码，错误消息是什么意思?

What can I do to fix my code, and what does the error message mean?

推荐答案

NewBox必须具有一个转发给父类的构造函数的构造函数.试试这个:

NewBox has to have a constructor that forwards to the parent class's constructor. Try this:

public class NewBox extends Box{ 

  public NewBox(String name) {
    super(name);
  }

  public void calculateVolume(int length, int width, int height){ 
    System.out.println("Volume = " + (length*width*height));
  }
}

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