Why does my java.util.Scanner not read my File?

Question

my Scanner doesn't read my existing File which is read by a BufferedReader but BufferedReaders don't support UTF-8 encoding which my file needs.

I've already used a BufferedReader(even with UTF-8 which didn't give me letters like "ä"(german letter) but gave me awkward question mark symbols instead). And I've of course already used a Scanner.

public ArrayList<String> getThemefile2() {
    Scanner s;
    try {
        s = new Scanner(themefile);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
        return new ArrayList<>();
    }
    ArrayList<String> list = new ArrayList<>();
    while (s.hasNextLine()) {
        list.add(s.nextLine());
    }
    s.close();
    return list;
}

It just returns an empty ArrayList, but doesn't trigger the FileNotFoundException. themefile is an existing File.

Have you debugged/added print statements to see what is happening with the code? Is the while loop entered? — GBlodgett, Jan 07 '19 at 22:17
Of course the while loop is not entered, because the returned ArrayList has a size of 0 — Mrln, Jan 07 '19 at 22:20
In your catch block you also return an empty `List`. Are you sure no error message is printed? — GBlodgett, Jan 07 '19 at 22:27

score 0 · Answer 1 · answered Jan 07 '19 at 22:17

0

You need to specify the encoding for the file, if it's anything other than your system default. In your case, this will be where you create the Scanner.

s = new Scanner(themefile, "UTF-8");

answered Jan 07 '19 at 22:17

Dawood ibn Kareem

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That's not my problem. My Problem is, that it doesn't find any line in my file – Mrln Jan 07 '19 at 22:19
OK, what happens if you check `themefile.exists()` before doing anything else? You've probably just got the wrong path in `themefile`. – Dawood ibn Kareem Jan 07 '19 at 22:20
No, because when I used the exact same file with a BufferedReader, it worked – Mrln Jan 07 '19 at 22:20
Your problem can be caused by the wrong filename, or by a file that can't be read, or by using the wrong encoding. Did you actually try my solution? – Dawood ibn Kareem Jan 08 '19 at 00:33

score 0 · Answer 2 · answered Jan 07 '19 at 22:22

0

Without the file to look at, we're all just guessing at the problem.

Here's one guess: there is no next line, therefore the while loop immediately breaks off, and you get an empty arraylist. This would be the case if there is no newline at all in the text file.

answered Jan 07 '19 at 22:22

rzwitserloot

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Shall I upload my file on a website? – Mrln Jan 07 '19 at 22:23

CodeMatrix · Accepted Answer · 2019-01-09T12:51:22.577

0

If you're using Java 8+ I would recommend to use Files#lines method:

try (Stream<String> stream = Files.lines(themeFile.toPath())) {
    stream.collect(Collectors.toList()); //need to be stored in a variable.
} catch (IOException e) {
    e.printStackTrace();
}

Documentations:

edited Jan 09 '19 at 12:51

answered Jan 07 '19 at 22:23

CodeMatrix

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This one also throws following error: java.io.UncheckedIOException: java.nio.charset.MalformedInputException: Input length = 1 – Mrln Jan 07 '19 at 22:31
@Marlon Check [this](https://stackoverflow.com/questions/30609062/java-nio-charset-malformedinputexception-input-length-1) to solve the exception. – CodeMatrix Jan 07 '19 at 22:32

score 0 · Answer 4 · answered Jan 29 '19 at 15:12

0

I had the same problem with api 28 level. This worked for me:

s = new Scanner(new FileReader(themefile));

and must import:

import java.io.FileReader;

answered Jan 29 '19 at 15:12

user1778258

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Why does my java.util.Scanner not read my File?

4 Answers4