Reading from Text file and parsing to ArrayList

Question

Solved adding `if (line.isEmpty()) continue;`

I need to read data from my text file and add this data into my ArrayList.

I see through debugger that the String[] words size is 1 which is "". That is why I get an exception :

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
    at java.lang.NumberFormatException.forInputString(Unknown Source)
    at java.lang.Integer.parseInt(Unknown Source)

My code is

List<Bill> list = new ArrayList<>();

try (BufferedReader reader = new BufferedReader(new FileReader("bill.txt"))) {
    String line;

    while ((line = reader.readLine()) != null) {
        String[] words = line.split(" ");
        Integer id = Integer.parseInt(words[0]);
        String venName = words[1];
        Double amount = Double.parseDouble(words[2]);
        LocalDate date = LocalDate.parse(words[3]);
        BillType bt = BillType.valueOf(words[4]);
        list.add(new Bill(venName, amount, date, bt, id));
    }
} catch(IOException e) {
    e.printStackTrace();
}

In this assignment I cannot use File and Object input/output Stream.
Could you please help me fix this bug?

What does the file look like? Does it have all the things you are trying to read from it? — clinomaniac
– clinomaniac, Commented Feb 27, 2018 at 18:56
Check the contents of String line, does it contains space separated values? — shriyog
– shriyog, Commented Feb 27, 2018 at 18:56
Check words.length == 5 before you proceed with each iteration — GalAbra
– GalAbra, Commented Feb 27, 2018 at 19:11
Are you sure of the content of your original text file? Is there perhaps a "\n" or "\r" inserted that you can't see? You should really run a check on the size of words before you attempt to extract values from it with magic numbers — NateH06
– NateH06, Commented Feb 27, 2018 at 19:21

Oleg Cherednik · Accepted Answer · 2018-02-27 19:51:38Z

You could use streams from Java 8. I think that using pattern with groups is much more clear that simple split string:

private static final Pattern WORDS = Pattern.compile("(?<id>\\d+)\\s+(?<name>[^\\s]+)\\s+(?<amount>[^\\s]+)\\s+(?<date>[^\\s]+)\\s+(?<type>[^\\s]+)");

public static List<Bill> readBillFile(String fileName) throws IOException {
    return Files.lines(Paths.get(fileName))
                .map(WORDS::matcher)
                .filter(Matcher::matches)
                .map(matcher -> {
                    int id = Integer.parseInt(matcher.group("id"));
                    String venName = matcher.group("name");
                    double amount = Double.parseDouble(matcher.group("amount"));
                    LocalDate date = LocalDate.parse(matcher.group("date"));
                    BillType bt = BillType.valueOf(matcher.group("type"));
                    return new Bill(venName, amount, date, bt, id);
                })
                .collect(Collectors.toList());
}

Or you can just add check for total words to your code:

while ((line = reader.readLine()) != null) {
    String[] words = line.split(" ");

    if(words.length < 5)
        continue;

    // ...
}

user unknown · Accepted Answer · 2018-02-28 01:39:21Z

0

How about using the Scanner class?

import java.io.*;
import java.time.*;

try (Scanner reader = new Scanner (new File ("bill.txt"))) {
    while (reader.hasNextLine()) {
        reader.useDelimiter ("[ \t\n]");
        Integer id = reader.nextInt ();
        String venName = reader.next ();
        Double amount = reader.nextDouble ();
        LocalDate date = LocalDate.parse (reader.next ());
//      Don't know about BillType class
        String bt = reader.next ();
//      Don't have Bill.class
//      list.add(new Bill (venName, amount, date, bt, id));
    }
} catch (IOException e) {
    e.printStackTrace();
}

answered Feb 28, 2018 at 1:39

user unknown

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