NoSuchElementException異常讀/掃描輸入

Question

這裏的主要問題是：

java.util.NoSuchElementException: No line found 
     at java.util.Scanner.nextLine(Unknown Source) 
     at ExamAnalysis.main(ExamAnalysis.java:21) 
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
     at java.lang.reflect.Method.invoke(Unknown Source) 
     at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:271) 

程序編譯和運行。這只是我要麼接近java.util.NoSuchElementException和我的五個錯誤（接近底部的（answer.charAt（i）== char）。下面是我的程序：

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

class ExamAnalysis 
{ 
    public static void main(String [] args) throws FileNotFoundException 
    { 
     Scanner keyboard = new Scanner(System.in); 
     System.out.println("Please type the correct answers to the exam questions, one right after the other: "); 
     String answers = keyboard.nextLine(); 
     System.out.println("Where is the file with all the student responses? "); 
     String responses = keyboard.nextLine(); 
     Scanner read = new Scanner(new File(responses)); 


     while (read.hasNextLine()) 
     { 
     for (int i = 0; i <= 10; i++) 
     { 
      responses = read.nextLine(); 
      int p = 1; 
      p += i; 
      System.out.println("Student " + p + " responses: " + responses.substring(0,10)); 
      } 
      System.out.println("Thank you for the data on 9 students. Here's the analysis: "); 
      resultsByStudents(responses, answers); 
      analysis(responses); 
      } 
     } 

     public static void resultsByStudents(String responses, String answers) 
      { 
      System.out.println ("Student #  Correct  Incorrect  Blank"); 
      System.out.println ("~~~~~~~~~  ~~~~~~~  ~~~~~~~~~  ~~~~~"); 
      int student = 0; 
      int correct = 0; 
      int incorrect = 0; 
      int blank = 0; 

     for (int i = 0; i <= 9; i++) 
     { 
      for (int j = 0; j <= responses.length(); j++) 
      { 
      if ((responses.charAt(j)) == answers.charAt(j)) 
      correct++; 
      else if ((responses.charAt(j)) != answers.charAt(j)) 
      incorrect++; 
      else 
      blank++; 
      } 
      System.out.println(student + "  " + correct + "  " + incorrect + "  " + blank); 
      student++; 
     }  
     } 

    public static void analysis(String responses) 
    { 
     System.out.println("QUESTION ANALYSIS (* marks the correct response)"); 
     System.out.println("~~~~~~~~~~~~~~~~~"); 


    //stores the percentage of each choice chosen 
    double A = 0; 
    double B = 0; 
    double C = 0; 
    double D = 0; 
    double E = 0; 
    double X = 0; 
    // tallys every variable chosen per question 

    for (int i = 0; i <= 10; i++) // go through all the questions 
    { 
    for (int j = 0; j <= responses.charAt(i); j++) //go through all the student responses 
    { 
     // variable that are being tallied 
     int chooseA = 0; 
     int chooseB = 0; 
     int chooseC = 0; 
     int chooseD = 0; 
     int chooseE = 0; 
     int chooseBlank = 0; 
    //variables take percentage of choices that have been chosen from each student 
     A = chooseA/9; 
     B = chooseB/9; 
     C = chooseC/9; 
     D = chooseD/9; 
     E = chooseE/9; 
     X = chooseBlank/9; 
     // variables that will print the asterisk with certain character of correct answer 
     String a = "A"; 
     String b = "B"; 
     String c = "C"; 
     String d = "D"; 
     String e = "E"; 
     String blank = "blank"; 


     if (responses.charAt(j) == A) 
     chooseA++; 
     else if (responses.charAt(j) == B) 
     chooseB++; 
     else if (responses.charAt(j) == C) 
     chooseC++; 
     else if (responses.charAt(j) == D) 
     chooseD++; 
     else if (responses.charAt(j) == E) 
     chooseE++; 
     else 
     chooseBlank++; 


    System.out.println("Question #" + i); 
     if (answers.charAt(i) == 'A') a = "A*"; // answers cannot be resolved(I already made it a global variable in my main method.) 
     else if (answers.charAt(i) == 'B') b = "B*";// answers cannot be resolved 
     else if (answers.charAt(i) == 'C') c = "C*";// answers cannot be resolved 
     else if (answers.charAt(i) == 'D') d = "D*";// answers cannot be resolved 
     else if (answers.charAt(i) == 'E') e = "E*";// answers cannot be resolved 
     System.out.println(a + "  " + b + "  " + c + "  " + d + "  " + e + "  " + blank); 
    System.out.println (chooseA + "  " + chooseB + "  " + chooseC + "  " + chooseD + "  " + chooseE + "  " + chooseBlank); 
    System.out.println (A + "  " + B + "  " + C + "  " + D + "  " + E + "  " + X); 
    } 
} 

}}

Answer 1

刪除for循環可以解決該問題。您只使用while(hasNextLine())檢查一次，但在for循環中調用read.nextLine() 10次。

for (int i = 0; i <= 10; i++) 
     { 
      responses = read.nextLine(); 
     ....... 
      } 

Answer 2

while (read.hasNextLine())   
{   
    for (int i = 0; i <= 10; i++)   
    {  
     responses = read.nextLine(); 
     int p = 1;   
     p += i;   
     System.out.println("Student " + p + " responses: " + responses.substring(0,10));    
    }    
    System.out.println("Thank you for the data on 9 students. Here's the analysis: ");    
    resultsByStudents(responses, answers);    
    analysis(responses);    
    }   
} 

你這裏的邏輯是混亂你。 read.nextLine（）; 「使掃描器前進到當前行並返回跳過的輸入，此方法返回當前行的其餘部分，不包括結尾處的任何行分隔符，位置設置爲下一行的開始位置。

所以你說，它有一條線嗎？如果是這樣，請閱讀下一個10 ... ... ... 11行，這不是你想要的。你不知道這一點是否有11條線。不知道這是什麼文本文件的樣子，但你會想這部分重組要麼說，「雖然它有一個下一行」或「閱讀11線」

Answer 3

int i = 0; 
int numberOfStudents = 9; 
while (i < numberOfStudents && read.hasNextLine()){ 
    responses = read.nextLine(); 
    i++; 
    System.out.println("Student " + i + " responses: " + responses.substring(0,10)); 
} 
System.out.println("Thank you for the data on "+ numberOfStudents +" students. Here's the  analysis: "); 
resultsByStudents(responses, answers); 
analysis(responses); 

我< numberOfStudents：品牌所需的插入數量

read.hasNextLine（）：檢查是否有來自控制檯的輸入。如果不是，程序等待輸入。

for (int i = 0; i <= 10; i++) 

計數從0 - > 10 = 11學生