这个关于java的程序出了什么问题

Question

这是要求用户输入的代码。这些错误即将来临 -

MyFirstJavaProgram.java:12: error: cannot find symbol
          Scanner in=new Scanner(System.in);
          ^
  symbol:   class Scanner
  location: class MyFirstJavaProgram
MyFirstJavaProgram.java:12: error: cannot find symbol
          Scanner in=new Scanner(System.in);
                         ^
  symbol:   class Scanner
  location: class MyFirstJavaProgram
2 errors

请向我解释这些错误

int a;
Scanner in=new Scanner(System.in);
System.out.println("enter a number");
a=in.nextInt();
double b=200;
double c=a+b;
System.out.println("sum is"+c);

Answer 1

import java.util.Scanner;

在源文件的顶部（包裹decalaration下方）缺失

Answer 2

位于package和class之间的顶部 import java.util.Scanner;