Question

我在阅读文件时遇到问题，我可以让它读取所有行，但是使用下一行中的第一条信息，或者它会在末尾添加一个空白行，混淆构造函数数组

import java.io.*;
import java.util.*;
public class StudentMain {
/**
 * @param args
 */

//(String fn, String ln, String pn, int id, boolean ft, int phn, boolean lj, String     con)
    //array and sorting variables
 public static studentConstructor[] stuArrayOrig;
 private static String[] stuArrayIdSort;
 private static String[] stuArrayNameSort;
 private static int i = 0;
 private static int lineCount = 0;
 private static int nElms = 0;
 //studentConstructor variables 
    public static String fn; //First Name
    public static String ln; //Last Name
    public static String pn; //Preferred Name
    public static int id;     //Student Id Number
    public static boolean ft;//Full-time Boolean
    public static int phn;   //Student Phone Number
    public static boolean lj;//Loving java Boolean
    public static String con;//Continuing 


 public static void StuRead()
 {

    Scanner inFile = null;
     try
     {
         inFile = new Scanner
                (new FileReader("Res/students.txt"));
     }
     catch (FileNotFoundException e)
     {
         // TODO Auto-generated catch block
         System.out.println("File Not Found");
         e.printStackTrace();
     }

        while (inFile.hasNextLine()){
                    inFile.useDelimiter(",|\\n"); //breaks the   lines into single info

                    ln = inFile.next();
                        System.out.println(ln);

                    fn = inFile.next();
                        System.out.println(fn);

                    pn = inFile.next();
                        System.out.println(pn);

                    id = inFile.nextInt();
                        System.out.println(id);

                    ft = inFile.nextBoolean();
                        System.out.println(ft);

                    phn = inFile.nextInt();
                        System.out.println(phn);

                    lj = inFile.nextBoolean();
                        System.out.println(lj);

                    con = inFile.next();
                        System.out.println(con);

                        studentConstructor st = new studentConstructor(ln, fn, pn, id, ft, phn, lj, con);
                        System.out.println(st);
                        //System.out.println("LINE");
                        stuArrayOrig[lineCount] = st;
                        inFile.nextLine();
                        System.out.println(stuArrayOrig[lineCount]);


                    lineCount++;`

文件输入示例：

Angelon Arouca,Lucas,,1472429,TRUE,407514687,TRUE,Confirmed
Cordovilla,Wilbert,,1472430,TRUE,407514688,FALSE,Confirmed
Danks,Joshua,,1472431,TRUE,407514689,TRUE,Confirmed

我得到的输出：

Angelon Arouca
Lucas

1472429
true
407514687
true
Confirmed

studentConstructor@29ba92bb
Exception in thread "main" java.lang.NullPointerException
at StudentMain.StuRead(StudentMain.java:73)
at StudentApp.main(StudentApp.java:10)

谁能看到我哪里出错？

Answer 1

您从未初始化stuArrayOrig，因此它是null，尝试访问它会导致NullPointerException。

一旦接近将其初始化为某个“安全”的大值：

public static studentConstructor[] stuArrayOrig = new studentConstructor[100];

但是，使用自我增长的ArrayList：

可能要容易得多

public static List<studentConstructor> stuArrayOrig = new ArrayList<>();

从文件读取到构造函数时获取空行

1 个答案: