Java: Reading bytes from a .txt file LINE BY LINE

Question

Please have a look at the following code

    import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class FileCopy2
{    public static          


        

Answer 1

If you want to manipulate any kind of file, never consider they contain textual data, and consider them as binary files, containing bytes. Binary files are read and written using input and output streams.

Here's an example of a method that reads a file and splits it into pieces of 1024 bytes written to N output files :

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileSplit {
    public static void main(String[] args) throws IOException {
        new FileSplit().splitFile(new File(args[0]));
    }

    private void splitFile(File file) throws IOException {
        FileInputStream fis = new FileInputStream(file);
        try {
            byte[] buffer = new byte[1024];
            // remaining is the number of bytes to read to fill the buffer
            int remaining = buffer.length; 
            // block number is incremented each time a block of 1024 bytes is read 
            //and written
            int blockNumber = 1;
            while (true) {
                int read = fis.read(buffer, buffer.length - remaining, remaining);
                if (read >= 0) { // some bytes were read
                    remaining -= read;
                    if (remaining == 0) { // the buffer is full
                        writeBlock(blockNumber, buffer, buffer.length - remaining);
                        blockNumber++;
                        remaining = buffer.length;
                    }
                }
                else { 
                    // the end of the file was reached. If some bytes are in the buffer
                    // they are written to the last output file
                    if (remaining < buffer.length) {
                        writeBlock(blockNumber, buffer, buffer.length - remaining);
                    }
                    break;
                }
            }
        }
        finally {
            fis.close();
        }
    }

    private void writeBlock(int blockNumber, byte[] buffer, int length) throws IOException {
        FileOutputStream fos = new FileOutputStream("output_" + blockNumber + ".dat");
        try {
            fos.write(buffer, 0, length);
        }
        finally {
            fos.close();
        }
    }
}