Question

Exception in thread "main" java.util.NoSuchElementException at java.base/java.util.Scanner.throwFo

1
Exception in thread "main" java.util.NoSuchElementException
at java.base/java.util.Scanner.throwFor(Scanner.java:937)
at java.base/java.util.Scanner.next(Scanner.java:1478)
at com.Eshyee.Prog.Progress.main(Progress.java:16)

package com.Eshyee.Prog;

import java.util.Scanner;

public class Progress {

public static void main(String[] args) {

Scanner in = new Scanner(System.in);
int n = in.nextInt();
in.close();
Student[] a=new Student[n];
Scanner up =new Scanner(System.in);
for(int i=0;i<n;i++) {
a[i]=new Student();
a[i].name=up.next();
a[i].id=up.next();
a[i].grade=up.nextInt();

}
up.close();
for(int i=0;i<n;i++) {
System.out.println(a[i].name);
System.out.println(a[i].id);
System.out.println(a[i].grade);
}
}
}

class Student{
String name;
String id ;
int grade;

}

Answer 1

import java.util.Scanner;

public class Progress {

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

//这里只能输入数字

int n = in.nextInt();

Student[] a = new Student[n];

Scanner up = new Scanner(System.in);

for (int i = 0; i < n; i++) {

a[i] = new Student();

a[i].name = up.next();

a[i].id = up.next();

a[i].grade = up.nextInt();

}

up.close();

in.close();

for (int i = 0; i < n; i++) {

System.out.println(a[i].name);

System.out.println(a[i].id);

System.out.println(a[i].grade);

}

}

}

class Student {

String name;

String id;

int grade;

}

这个是正确的代码,原因出在第一个scanner类你将他close()了,当调用close()后，System.in这个流将会关闭，所以也就影响到了第二个scanner了，导致不能接受数据，从而引发java.util.NoSuchElementException.