异常在线程“主要” java.lang.Error的：未解决的编译问题：

Question

这是我得到

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    Scanner cannot be resolved to a type 
    Scanner cannot be resolved to a type 

    at hello.main(hello.java:11) 

这是我的代码错误。像import java.util.Scanner;

Answer 1

你有进口Scanner类你需要：

import java.util.Scanner; 

在你的文件的顶部。你必须导入它。

Answer 2

public class hello { 

    public static void main(String[] args) { 
     // TODO Auto-generated method stub 

     double area; 
     double radius; 

     Scanner input = new Scanner(System.in); 
     System.out.print("반지름을 입력하시오: "); 
     radius = input.nextDouble(); 
     area = 3.14 * radius * radius; 

     System.out.println(area); 
    }  
}