Exception in thread "main" java.lang.NumberFormatException: For input string: "" in Java

Question

I created a class in java to read a text file (.txt) and print on the screen the result on the screen. Script is reading the contents of the text file, but at the end it is displaying the message:

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:592)
at java.lang.Integer.parseInt(Integer.java:615)
at com.desafioProgramacao.LerArquivo.main(LerArquivo.java:24)

I do not know why it displays the message. In the FINALLY class I tell it to close the FileReader and the BufferedReader if the contents of the file are null. Follow the Java code and screen prints.

public class LerArquivo {

private static final String NomeArquivo = "E:\\DesafioProgramacao\\matriculasSemDV.txt";

public static void main(String[] args) {

    FileReader fr = null;
    BufferedReader br = null;

    try {
        fr = new FileReader(NomeArquivo);

        br = new BufferedReader(fr);

        String sCurrentLine;

        while ((sCurrentLine = br.readLine()) != null) {
            int num = Integer.parseInt(sCurrentLine);
            System.out.println(num);
        }
    } catch (IOException e) {
        e.printStackTrace();

    } finally {

        try {
            if (br != null) {

                br.close();

            }

            if (fr != null) {

                fr.close();
            }
        } catch (IOException ex) {

            ex.printStackTrace();
        }
    }
}}

Looks like your text file has an extra line at the end.

Jacob G.
– Jacob G.

2018-04-19 15:38:06 +00:00
Commented Apr 19, 2018 at 15:38 — Jacob G.
– Jacob G., Commented Apr 19, 2018 at 15:38
Maybe you got an empty line at the end of your file

Robert Kock
– Robert Kock

2018-04-19 15:38:27 +00:00
Commented Apr 19, 2018 at 15:38 — Robert Kock
– Robert Kock, Commented Apr 19, 2018 at 15:38

Alberto · Accepted Answer · 2018-04-19 15:40:38Z

2

The problem is the last line, it is a blank space. You can do:

while ((sCurrentLine = br.readLine()) != null) {
    if (!sCurrentLine.isEmpty()) {
        int num = Integer.parseInt(sCurrentLine);
        System.out.println(num);
    }
}

answered Apr 19, 2018 at 15:40

Alberto

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Comments

flyingfox · Accepted Answer · 2018-04-19 15:44:55Z

2

The cause on the surface is that your read an empty string and want to parse it to int

For the code,you need check the sCurrentLine value

while ((sCurrentLine = br.readLine()) != null) {
    if(StringUtils.isNotBlank(sCurrentLine)){//StringUtils is from `commons-lang` 
     // or if(sCurrentLine.length()>0)
     int num = Integer.parseInt(sCurrentLine);
     System.out.println(num);
    }
}

For the txt file,you need to remove all the empty line at the end of the file

edited Apr 19, 2018 at 15:44

answered Apr 19, 2018 at 15:40

flyingfox

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3 Comments

k_ssb Over a year ago

Why not !sCurrentLine.isEmpty()? No need to involve Apache Commons for such a simple problem.

flyingfox Over a year ago

Because need to check if it has more than one empty space and I am not sure if sCurrentLine.isEmpty() can check for it

Dorian Gray Over a year ago

Why not just call parseInt(..) catch that Exception instead of considering all possible cases in advance?

xingbin · Accepted Answer · 2018-04-19 15:45:26Z

1

Your file contains an empty line (probably at the end).

Replace your while loop with:

while ((sCurrentLine = br.readLine()) != null && !sCurrentLine.isEmpty())

edited Apr 19, 2018 at 15:45

xingbin

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answered Apr 19, 2018 at 15:38

k_ssb

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Comments

Dorian Gray · Accepted Answer · 2018-04-19 17:01:05Z

0

The correct way to fix it is to catch that NumberFormatException and handle it properly, like that:

         try {
            int num = Integer.parseInt(sCurrentLine);
            System.out.println(num);
        } catch (NumberFormatException ex) {
            System.out.println("Error reading line: " + sCurrentLine);
        }

answered Apr 19, 2018 at 17:01

Dorian Gray

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