未定义的构造函数 (java) [英] Undefined constructor (java)

问题描述

所以我有一个名为 User 的 java 类，它包含一个像这样的构造函数:

so I have a java class called User that contains a constructor like this:

public class User extends Visitor {
    public User(String UName, String Ufname){
        setName(UName);
        setFname(Ufname);
    }
}

然后他的问题出现在我的另一个名为 Admin 的班级中:

And then the he problems occur in my other class called Admin:

public class Admin extends User {  //error "Implicit super constructor User() is undefined for default constructor. Must define an explicit constructor"

//public Admin() { } //tried to add empty constructor but error stays there

    //}


    public void manage_items() {            

        throw new UnsupportedOperationException();
    }

    public void manage_users() {   

        throw new UnsupportedOperationException();
    }
}

我收到错误 默认构造函数未定义隐式超级构造函数 User().必须在代码中标记的地方定义一个显式构造函数. 我不知道如何解决这个问题，而且我真的是 Java 新手.

I am getting the error Implicit super constructor User() is undefined for default constructor. Must define an explicit constructor at the place marked in the code. I don't know how to fix that, and I'm really new to java.

推荐答案

你必须在第一个扩展 Visitor 的构造函数上调用 Visitor 的构造函数的类，使用 super():

You must call the Visitor's constructor on the first like of the constructor that extends the Visitor's class, using super():

public User(String UName,String Ufname){
    super();
    setName(UName);
    setFname(Ufname);
}

如果您也希望 Admin 拥有自定义构造函数，则必须调用:

and if you want Admin to have a custom constructor too, you must call:

super(uname, ufname) // String, String - pass the params of the superclass cunstructor

所以:

public Admin() {
    super(someString, someString);
}

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