Question

我已经跟踪了这段代码，无法弄清楚如何修复它。运行代码时，为什么不提示用户输入而不是Java确定没有输入？错误跟踪如下。

import java.util.*;
public class SortAsInserted {

    public static void main(String[] args) {
        int array_size = GetArraySize();
        //System.out.println(array_size);
        String[] myArray = new String[array_size];
        for (int i = 0; i < array_size; i++){
            String next_string = GetNextString();
            System.out.println(next_string);
        }
    }



    //public static String[] SortInsert(String nextString){
        //}

    public static int GetArraySize(){
        Scanner input = new Scanner(System.in);
        System.out.print("How many items are you entering?: ");
        int items_in_array = input.nextInt();
        input.close();
        return items_in_array;


    }

    public static void PrintArray(String[] x) {
        for (int i = 0; i < x.length; i++){
            System.out.print(x[i]);
        }

    }

    public static String GetNextString(){
        Scanner input = new Scanner(System.in);
        System.out.println("Enter the next string: ");
        String next_string = input.nextLine();
        input.close();
        return next_string;

        }

这是错误 -

How many items are you entering?: 2
Enter the next string: 
Exception in thread "main" java.util.NoSuchElementException: No line found
    at java.util.Scanner.nextLine(Unknown Source)
    at SortAsInserted.GetNextString(SortAsInserted.java:40)
    at SortAsInserted.main(SortAsInserted.java:10)

Answer 1

简单的答案是当您关闭扫描程序时 - 基础输入流也会关闭： http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#close()

要在main中修复此创建扫描程序一次：

 public class SortAsInserted {
     static Scanner input;
     public static void main(String[] _) {
         input = new Scanner(System.in); 
         ....
         input.close();  
     }

Answer 2

从代码中删除input.close();

Answer 3

从两个函数中删除scanner.close（）方法将解决您的问题。

import java.util.*;
public class SortAsInserted {

    public static void main(String[] args) {
        int array_size = GetArraySize();
        //System.out.println(array_size);
        String[] myArray = new String[array_size];
        for (int i = 0; i < array_size; i++){
            String next_string = GetNextString();
            System.out.println(next_string);
        }
    }



    //public static String[] SortInsert(String nextString){
        //}

    public static int GetArraySize(){
        Scanner input = new Scanner(System.in);
        System.out.print("How many items are you entering?: ");
        int items_in_array = input.nextInt();
        //input.close();
        return items_in_array;


    }

    public static void PrintArray(String[] x) {
        for (int i = 0; i < x.length; i++){
            System.out.print(x[i]);
        }

    }

    public static String GetNextString(){
        Scanner input = new Scanner(System.in);
        System.out.println("Enter the next string: ");
        String next_string = input.nextLine();
       // input.close();
        return next_string;

        }
 }

为什么这段代码会出现Java NoSuchElementexception？

3 个答案: