无法使用Scanner类，构造函数未定义，方法未定义 [英] Can't use Scanner class, constructor is undefined, method is undefined

问题描述

当我希望在我的项目eclipse中导入扫描器类时显示一些错误：

When i want import scanner class in my project eclipse show me some errore :

 Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
  The constructor Scanner(InputStream) is undefined
  The method nextLine() is undefined for the type Scanner

这是我的代码：

import java.util.Scanner;

public class Scanner {

    public static void main(String[] args) {

        Scanner myScanner = new Scanner(System.in);
        System.out.println(myScanner.nextLine());

    }

}

推荐答案

问题在于，您还声明一个名为 Scanner 的类。这意味着当您然后声明一个类型为 Scanner 的变量，并尝试调用构造函数时，编译器会认为您正在谈论您的类。只需将自己的课程改成别的东西（例如 Test ）：

The problem is that you're also declaring a class called Scanner. That means that when you then declare a variable of type Scanner and try to call the constructor, the compiler thinks you're talking about your class. Just change your own class to something else (e.g. Test):

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        Scanner myScanner = new Scanner(System.in);
        System.out.println(myScanner.nextLine());
    }
}

或者你可以当您的意思是 java.util.Scanner 时，可以完全限定名称，但这在可读性方面是一个坏主意。

Alternatively you could just fully-qualify the name when you mean java.util.Scanner - but this would be a bad idea in terms of readability.

// Please don't do this - but it would work.
public class Scanner {
    public static void main(String[] args) {
        java.util.Scanner myScanner = new java.util.Scanner(System.in);
        System.out.println(myScanner.nextLine());
    }
}

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