CODEWITHSUNDEEP
javajava.util.scanner
Gaurav Jeswani
Gaurav Jeswani

Reputation: 4592

Complete file read at once using scanner in java

I have to read a text file in Java, for that I am using below code:

Scanner scanner = new Scanner(new InputStreamReader(
    ClassLoader.getSystemResourceAsStream("mock_test_data/MyFile.txt")));

scanner.useDelimiter("\\Z");
String content = scanner.next();
scanner.close();

As far as I know String has MAX_LENGTH 2^31-1

But this code is reading only first 1024 characters from input file(MyFile.txt).

I am not able to find the reason.

Upvotes: 2

Views: 1370

Answers (3)

Gaurav Jeswani
Gaurav Jeswani

Reputation: 4592

Thanks for your answers:

Finally I have found solution for this-

 String path = new File("src/mock_test_data/MyFile.txt").getAbsolutePath();
 File file = new File(path);
 FileInputStream fis = new FileInputStream(file);
 byte[] data = new byte[(int) file.length()];
 fis.read(data);
 fis.close();
 content = new String(data, "UTF-8");

As i have to read a very long file at once.

Upvotes: 2

Doe Johnson
Doe Johnson

Reputation: 1414

I've read some of the comments and therefore I think it's necessary to point out that this answer does not care about good or bad practice. This is a stupid nice-to-know scanner trick for lazy people who need a quick solution.

final String res = "mock_test_data/MyFile.txt"; 

String content = new Scanner(ClassLoader.getSystemResourceAsStream(res))
     .useDelimiter("\\A").next();

Stolen from here...

Upvotes: 2

Aleksandar
Aleksandar

Reputation: 1173

Example of using BufferedReader, works great for big files:

public String getFileStream(final String inputFile) {
        String result = "";
        Scanner s = null;

        try {
            s = new Scanner(new BufferedReader(new FileReader(inputFile)));
            while (s.hasNext()) {
                result = result + s.nextLine();
            }
        } catch (final IOException ex) {
            ex.printStackTrace();
        } finally {
            if (s != null) {
                s.close();
            }
        }
        return result;
}

FileInputStream is used for smaller files.

Using readAllBytes and encoding them solves problem as well.

static String readFile(String path, Charset encoding) 
  throws IOException 
{
  byte[] encoded = Files.readAllBytes(Paths.get(path));
  return new String(encoded, encoding);
}

You can take a look at this question. It is very good.

Upvotes: 0

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