线程中的 Java 异常 "main"java.util.NoSuchElementException 运行时错误

Question

我一直在制作一个简单的java程序作为学校的家庭作业。当我添加从 .txt 文件检索二维数组的方法时，出现了此错误。该程序在编译时不会显示任何错误。我是一名新程序员，因此请彻底检查所有添加或更改的内容。除了手头的问题之外，请随时给我进一步的提示和建议。

提前致谢

这是代码:

import java.util.*;
import java.io.*;

public class simpleAI2
{

   public static void main (String [] args)
   {
      int count = 0;
      String[][] array = new String [20][4];
      simpleAI2.getArrayData(array);
      String leaveQ;
      int rep = 1;

      do
      {
         int countTwo = 0;
         boolean flag = false;
         Scanner scanName = new Scanner (System.in);
         Scanner scanSport = new Scanner (System.in);
         Scanner leave = new Scanner (System.in);


         System.out.println("My name is A.I.S.C.M.B.T. What is your name?");
         array[count][1] = scanName.nextLine ();
         System.out.println("Hi "+array[count][1]+"! What's your favourite sport?");
         array[count][2] = scanSport.nextLine ();
         String sport = array[count][2];

         for(int x = 1;x<rep;x++)
         {
            if(!array[countTwo][2].equals(null) && array[countTwo][2].equals(array[count][2]))
               {
               flag = true;
               x = 28;
               }

            else
               {
               flag = false;
               }

            countTwo ++;
         }


         countTwo --;

         if(flag == true)
            {
            System.out.println("I know "+array[countTwo][2]+". It is "+array[countTwo][3]+". My friend "+array[countTwo][1]+" knows it");
            }

         if(flag == false)
            {
            System.out.println("I don't know "+array[count][2]+". I only know robot boxing. Robots hit each other until one malfunctions. What is this alien sport you speak of?");
            array[count][3] = scanSport.nextLine ();
            }

         System.out.println("Go again? Type no to leave me :(");
         leaveQ = leave.nextLine ();

         rep ++;

         count ++;

         if(leaveQ.equals("no"));
            {
            simpleAI2.Save(array);
            }

      }while (!leaveQ.equals("no"));

   }



   public static void Save(String [][] array){

      try {
         PrintWriter writer = new PrintWriter(new File("arrayData.txt"));

         for(int x=0; x<array.length; x++){
            for(int y=0; y<array[x].length; y++){
               writer.write(String.valueOf(array[x][y]));
            }
            writer.println(); 
         }

         writer.flush();  
         writer.close();        



      } 
      catch (FileNotFoundException e) 
         {      
         e.printStackTrace();
         }


   }

   public static void getArrayData(String [][] array){

      try {
         Scanner scan2 = new Scanner(new File("arrayData.txt"));

         for(int i=0; i<array.length;  i++){
            for(int j=0; j<array[i].length; j++)
            {
               array[i][j]=scan2.next(); 


            }
         }


      } 

      catch (FileNotFoundException e)
         { 
         e.printStackTrace(); 
         }    

   }
}

Answer 1

如果调用Scanner函数next()当没有任何内容可供读取时，它将抛出 NoSuchElementException。
将您的代码更改为以下内容:

public static void getArrayData(String [][] array)
{
    try 
    {
        Scanner scan2 = new Scanner(new File("arrayData.txt"));

        for(int i=0; i<array.length;  i++)
        {
            for(int j=0; j<array[i].length; j++)
            {
                if ( ! scan2.hasNext() )  //if there's nothing left to read
                    return;               //exit the function

                array[i][j]=scan2.next(); 
            }
        }
    } 
    catch (FileNotFoundException e)
    { 
        e.printStackTrace(); 
    }    

}