Read a txt File with RandomAccessFile (Java)

Question

I try to output the content of a text file. But I don't know how to work with the RandomAccessFile. I haven't found good examples at google. I hope for some help.

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

public class ReadTextFile {

    public static void main(String[] args) throws IOException {

        File src = new File ("C:/Users/hansbaum/Documents/Ascii.txt");
        cat(src);
    }

    public static void cat(File quelle){
        try (RandomAccessFile datei = new RandomAccessFile(quelle, "r")){

//          while(datei.length() != -1){        
//              datei.seek(0); //
//          }               
        } catch (FileNotFoundException fnfe) {
            System.out.println("Datei nicht gefunden!");
        } catch (IOException ioe) {
            System.err.println(ioe);
        }
    }
}

Answer 1

related from doc

try (RandomAccessFile datei = new RandomAccessFile(quelle, "r")){
        String line;
        while ( (line = datei.readLine()) != null ) {
            System.out.println(line);
        }

        System.out.println();
    } catch (FileNotFoundException fnfe) {
    } catch (IOException ioe) {
        System.err.println(ioe);
    }

Answer 2

What makes you think you need a RandomAccessFile? The easiest way is probably to use nio's convenience methods. With those, reading a file is as close to a one-liner as it gets in Java.

import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.io.IOException;
class Test {
  public static void main(String[] args) throws IOException {
    List<String> lines = Files.readAllLines(Paths.get("./Test.java"), StandardCharsets.UTF_8);
    for (String l: lines)
      System.out.println(l);
  }
}

Be aware however that this is not a good idea if you happen to work with very large files as they might not fit into memory.

Answer 3

Try to create Stream from FileChannel to read and write in another file out.txt like this:

        try (RandomAccessFile datei = new RandomAccessFile(quelle, "r").getChannel();){

        // Construct a stream that reads bytes from the given channel.
        InputStream is = Channels.newInputStream(rChannel);

        File outFile = new File("out.txt");

        // Create a writable file channel
        WritableByteChannel wChannel = new RandomAccessFile(outFile,"w").getChannel();

        // Construct a stream that writes bytes to the given channel.
        OutputStream os = Channels.newOutputStream(wChannel);

        // close the channels
        is.close();
        os.close();