每次我編譯while循環超出了我的項目一切不露面（輸入來自文件）

Question

import java.io.*; 
import java.util.*; 
public class Statistics { 

    public static void main(String[] args) throws IOException { 
     Scanner in = new Scanner(new FileReader("C:\\Users\\user\\Desktop\\students.dat"));//Opened file 

     int math=0,spanish=0,french=0,english=0,count=0,sum,highSpan=0,highMath=0,highFren=0,highEng=0;//Declarations 
     double avg,highAvg=0; 
     String name,highName; 
     highName=""; 
     name = "";      //Prime read 
      while (name!="ENDDATA"){  //Sentinel condition 
       count++;     //Keeps count of students 
       name = in.next(); 
       spanish=in.nextInt(); 
       math=in.nextInt(); 
       french=in.nextInt(); 
       english=in.nextInt(); 
       sum = spanish + math + french + english; 
       avg = sum/4;         //Claculates Average 
       System.out.printf("%s - %.0f\n",name,avg); 

        if (avg > highAvg){       //Checks for the highest Average 
         highAvg = avg; 
         highName = name; 
        } 
        if (spanish > highSpan){ 
         highSpan = spanish; 
        } 
        if (math > highMath){ 
         highMath = math;      //Checks for the highest mark for each subject 
        } 
        if (french > highFren){ 
         highFren = french; 
        } 
        if (english > highEng){ 
         highEng = english; 
        } 

       name = in.nextLine(); 
      } 

     System.out.printf("Number of students in class is: %d\n",count); 
     System.out.printf("The highest student average is: %f\n",highAvg); 
     System.out.printf("The student who made the highest average is: %s\n",highName); 
     System.out.printf("The highest Spanish mark is: %d\n",highSpan); 
     System.out.printf("The highest Math mark is: %d\n",highMath); 
     System.out.printf("The highest French mark is: %d\n",highFren); 
     System.out.printf("The highest English mark is: %d\n",highEng); 
     in.close();                 //Closing of file 
    } 
} 

寫Java程序讀取和處理文本文件的每一行，並打印以下 信息（每個最後一行除外）： 該班級中的學生人數 每名學生的姓名和平均分數 班級中的最高學生平均分（忽略平局的可能性） 獲得最高平均分的學生的名字（忽略配合的可能性） 每個科目的最高分數

其應該讀取的數據形式的數據文件，並作出必要的輸出，但在while循環外的打印語句不顯示，我也得到這個輸出與下面的錯誤。

MARY - 65 
SHELLY - 70 
JOHN - 60 
ALFRED - 71 
Exception in thread "main" java.util.NoSuchElementException 
    at java.util.Scanner.throwFor(Scanner.java:862) 
    at java.util.Scanner.next(Scanner.java:1485) 
    at java.util.Scanner.nextInt(Scanner.java:2117) 
    at java.util.Scanner.nextInt(Scanner.java:2076) 
    at Statistics.main(Statistics.java:17) 

Answer 1

in.nextInt（）拋出NoSuchElementException。

您的文件似乎有不正確的數據。

while循環將永遠不會因爲你的病情突破：

while(name!="ENDDATA") 

永遠是正確的。這就是爲什麼當所有令牌都用盡時，scanner對象會拋出NoSuchElementException異常。由於while循環之後的print語句沒有執行，所以這是個例外。

嘗試使用hasNext（）掃描儀的方法檢查下一個標記。

用這個代替你的while循環。

while (in.hasNext()){  //Sentinel condition 
      count++;     //Keeps count of students 
      name = in.next(); 
      if(name.equals("ENDDATA")){ 
       break; 
      } 
      spanish=in.nextInt(); 
      math=in.nextInt(); 
      french=in.nextInt(); 
      english=in.nextInt(); 
      sum = spanish + math + french + english; 
      avg = sum/4;         //Claculates Average 
      System.out.printf("%s - %.0f\n",name,avg); 

       if (avg > highAvg){       //Checks for the highest Average 
        highAvg = avg; 
        highName = name; 
       } 
       if (spanish > highSpan){ 
        highSpan = spanish; 
       } 
       if (math > highMath){ 
        highMath = math;      //Checks for the highest mark for each subject 
       } 
       if (french > highFren){ 
        highFren = french; 
       } 
       if (english > highEng){ 
        highEng = english; 
       } 


} 

學生。dat文件格式應該如下所示：

Shelly 2 2 3 4 
Brown 34 2 1 4 
Pink 23 45 21 1 
ENDDATA 

Answer 2

也許這是因爲在while循環中name = in.next（）和name = in.nextLine（）。我認爲一個就足夠了。 例如：

name = in.next（）;
do {
.....
....
name = in.next（）;
} while（name！=「ENDDATA」）;

Answer 3

問題似乎在線french=in.nextInt()。如documentation所述，nextInt()將在沒有更多輸入要讀取時拋出NoSuchElementException。

公衆詮釋nextInt（）

拋出：

NoSuchElementException - 如果輸入信息已耗盡

大概在student.dat條目中的一個未填寫你希望它是方式。