读取CSV文件，数组索引越界错误

Question

I'm attempting to read in a csv file, I've created a test file with 9 entries and their value, but my code won't read past the second line , it says the file isn't found past the second key, I've tried tweeking it as much as possible, can someone help me? sample input would include something like this but in a csv file (so each in a new line, I'm new here and still learning to edit text here): Diego,2 Maria,2 Armando,5 Ken, 1

public static void main(String[] args) {

    HashMap<String, Integer> h = new HashMap<String, Integer>(511);


    try
    {
        Scanner readIn = new Scanner (new File ("test1.csv") );
        System.out.println("I'm here 1");


        while ( readIn.hasNext() )
        {               

            System.out.print(readIn.next());// for testing purposes only
            System.out.println("Check 2"); // for testing purposes only 


            String line = readIn.nextLine();
            String str[] = line.split(",");

            for (int i = 0; i < str.length ; i++)
            {
                String k = str[0];
                int v = Integer.parseInt(str[1]);
                h.insert(k , v);
            }

            System.out.println(h.toString());

        }
        readIn.close();     
    }

    catch (ArrayIndexOutOfBoundsException ob)
    {
        System.out.println(" - The file wasn't found." );
    } 

    catch (FileNotFoundException e) 
    {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

Answer 1

A call to next() or nextLine() should be preceeded with the call to hasNext().But in you code you have checked if hasNext() returns true in the while loop,and then invoked both next() and nextLine() inside the loop. You can modify your code as below:

while ( readIn.hasNext() )
            {               

                String line = readIn.nextLine();
                String str[] = line.split(",");

                for (int i = 0; i < str.length ; i++)
                {
                    String k = str[0];
                    int v = Integer.parseInt(str[1]);
                    h.put(k , v);
                }

                System.out.println(h.toString());

            }

Answer 2

Your for loop isn't actually serving a purpose. You will notice that you never actually reference i in the loop. Prior to the OP's answer I believe you were trying to split on a string that didn't have a comma, but your code assumes that one will be there and hence the out of bounds exception. This relates to why I was telling you that the println() was problematic.

As far as your question about hasNext() , this is the only way you will know that you can read another line from the file. If you try to read past the end you will run into problems.

Answer 3

Rather writing code to read CSV file on your own. I'd suggest you to use standard libraries like Apache Commons CSV . It provides more methods to deal with CSV , Tab separated file , etc...

import java.io.FileReader;
import java.util.List;

import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVRecord;

public class SO35859431 {
    public static void main(String[] args) {
        String filePath = "D:\\user.csv";
        try {
            List<CSVRecord> listRecords = CSVFormat.DEFAULT.parse(new FileReader(filePath)).getRecords();
            for (CSVRecord csvRecord : listRecords) {
                /* Get record using index/position */
                System.out.println(csvRecord.get(0));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Answer 4

First there is no such insert() method in HashMap class.The correct one is put(k, v) & in while loop it should be hasNext(). Follow is my code alternate the BufferedReader.

/* * To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */ package read;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Scanner;

/**
 *
 * @author Isuru Rangana Jr
 */
public class Read {

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) throws FileNotFoundException, IOException {
        HashMap<String, Integer> h = new HashMap<String, Integer>();

        try {
            BufferedReader readIn = new BufferedReader(new FileReader(new File("test.csv")));

            while (readIn.ready()) {

                String line = readIn.readLine();
                String str[] = line.split(",");


                for (int i = 0; i < str.length; i++) {
                    String k = str[0];
                    int v = Integer.parseInt(str[1]);
                    h.put(k, v);
                }

                System.out.println(h.toString());

            }
            readIn.close();
        } catch (ArrayIndexOutOfBoundsException ob) {
            System.out.println(" - The file wasn't found.");
        }
    }

}