从文件读取并存储

Question

I am trying to read a file and store it using hashmap, but there is this error "java.lang.ArrayIndexOutOfBoundsException: 0". My input has two columns separated by space something like Name ID so on with different entries. Help is appreciated. Thanks.

Input:

Mary ID
Mary Lastname
Mary Place
Mary DOB
Mary Homepage
Mary Postcode
John ID
John Lastname
John Place
John DOB
John Homepage
John Postcode

Code:

import java.util.*;

class ReadFileAndStoreHashmap {
    public static void main(String[] args)  {
        try{
            Scanner scanner = new Scanner(new FileReader(".txt"));

            HashMap<String, String> map = new LinkedHashMap<String, String>();

            while (scanner.hasNextLine()) {
                String[] columns = scanner.nextLine().split(" ");
                map.put(columns[0], columns[1]);
                System.out.println(map);
            }
        }
        catch (Exception e) {
            System.out.println(e.toString());
        }
    }
}

Answer 1

I would check the line you're attempting to scan. I suspect it's blank and hence the scanner can't split it as desired.

I would recommend asserting/checking on the length of the returned array. If it doesn't have 2 elements then you can easily report this and continue or break as desired, whilst reporting to the user what's gojne wrong.

Answer 2

Most likely you have an empty line somewhere (does you file end with a newline? Then there is an empty line after it, probably.)

add a check like

if(columns.length == 2) 

Answer 3

I prefer to use BufferedReader personally.

Here is my suggestion:

try {
    String line;
    BufferedReader filestart = new BufferedReader(new FileReader(file));
    for (line = filestart.readLine(); line !=null; line = filestart.readLine()) {

          String[] columns = line.split(" ");
          map.put(columns[0], columns[1]);
          System.out.println(map);

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

Having "line != null" should ensure you can definitely split the line, before you try.