PTA"cannot find symbol"报错 可以帮我看看有什么问题吗(语言-java)

Question

报错：

Main.java:5: error: cannot find symbol
Scanner in = new Scanner(System.in);
^
symbol: class Scanner
location: class Main
Main.java:5: error: cannot find symbol
Scanner in = new Scanner(System.in);
^
symbol: class Scanner
location: class Main
Main.java:14: error: cannot find symbol
int a[] = Arrays.copyOf(arr, n);
^
symbol: variable Arrays
location: class Main
Main.java:15: error: cannot find symbol
int b[] = Arrays.copyOfRange(arr, n, m);
^
symbol: variable Arrays
location: class Main
4 errors

我的代码：

public class Main {

public static void main(String[] args) {
    
    Scanner in = new Scanner(System.in);
    int n = in.nextInt();
    int sum = 0;
    if(n>=1&&n<=10) {
        int m = 2*n;
        int[]arr = new int[m];
        for(int i=0;i<m;i++) {
            arr[i] = in.nextInt();
        }
        int a[] = Arrays.copyOf(arr, n);
        int b[] = Arrays.copyOfRange(arr, n, m);
        for(int k=0;k<n;k++) {
            
            sum = a[k]*b[k]+sum;
        }
        System.out.println(sum);
    }    
        
}

}

我的尝试纠错：

在Scanner前面加上class后报错得寸进尺，让我再加一个class

Arrays前面加了variable也无法得到改善

在PTA上报错，但是在eclipse上是可以正常编译运行的

我想要达到的结果：

输入样例:
3
1 2 3 4 5 6
输出样例:
32

Answer 1

你有没有
import java.util.Scanner;