我有一个带有静态方法的测试类来获取输入。 class Test { public static Student readStudent() throws IOException { Scanner s = new Scanner(System.in); System.out.println("Enter first name of student"); String fname = s.nextLine(); System.out.println("Enter middle name of student"); String mname = s.nextLine(); System.out.println("Enter last name of student"); String lname = s.nextLine(); System.out.println("Enter name format(1 for ',' and 2 for ';') "); int num = s.nextInt(); System.out.println("Enter age of student"); int age = s.nextInt(); s.close(); return new Student(new Name(String.join((num == 1) ? "," : ";", fname, mname, lname)), age); } }我能够接受一名学生的输入，但是一旦我将其放入 for 循环中，我就会收到错误java.util.NoSuchElementException: No line found。这是我的循环for (int i = 0; i < 10; i++) { Student s = Test.readStudent(); }为什么我会收到此错误？谢谢。
1 回答
慕侠2389804
TA贡献1719条经验 获得超6个赞
s.close();关闭当前Scanner对象，以及所有底层流（System.in在本例中就是如此）。一旦标准输入流关闭，您就无法再打开它。
因此，总而言之，在确定不再需要扫描仪并重新构建代码后，最好关闭它，如下所示：
Scanner sc = new Scanner(System.in);
for (int i = 0; i < 10; i++) {
Student s = Test.readStudent(sc);
// do something with your student object here
}
sc.close();
并将你的方法更改为
public static Student readStudent(Scanner s) throws IOException {
Scanner s = new Scanner(System.in);
System.out.println("Enter first name of student");
String fname = s.nextLine();
System.out.println("Enter middle name of student");
String mname = s.nextLine();
System.out.println("Enter last name of student");
String lname = s.nextLine();
System.out.println("Enter name format(1 for ',' and 2 for ';') ");
int num = s.nextInt();
s.nextLine(); // Need to consume new line
System.out.println("Enter age of student");
int age = s.nextInt();
s.nextLine(); // Need to consume new line
// no closing here
return new Student(new Name(String.join((num == 1) ? "," : ";", fname,
mname, lname)), age);
}
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