package textgen;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.nio.charset.Charset;
import java.util.Random;

public class TextGen {

    private static final String PATH_SRC = "C:\\Documents and Settings\\User\\Рабочий стол\\src.txt";
    private static final Charset CHARSET = Charset.forName("Cp1251");

    public static void main(String[] args) throws FileNotFoundException, IOException {
        FileOutputStream fos = new FileOutputStream(PATH_SRC);
        OutputStreamWriter osw = new OutputStreamWriter(fos, CHARSET);
        Random r = new Random(System.currentTimeMillis());
//        for (int i = 1; i < 50_000_001; ++i) { //650Mb
        for (int i = 1; i < 710_001; ++i) { //8Mb
            osw.write("слово");
            osw.write(Integer.toString(i));
            osw.write(r.nextBoolean() ? " " : "\n");
        }
        osw.flush();
    }
}

package textparse;

import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import static java.nio.channels.FileChannel.MapMode.READ_ONLY;

public class TextParse {

    private static final String
            PATH_SRC = "C:\\Documents and Settings\\User\\Рабочий стол\\src.txt",
            PATH_OUT = "C:\\Documents and Settings\\User\\Рабочий стол\\out.txt";
    private static final byte SEPARATOR[] = {0xD, 0xA};

    public static void main(String[] args) throws FileNotFoundException, IOException {
        long timeStart = System.currentTimeMillis();

        RandomAccessFile randomAccessFile = null;
        BufferedOutputStream os = null;
        try {
            randomAccessFile = new RandomAccessFile(PATH_SRC, "r");
            os = new BufferedOutputStream(new FileOutputStream(PATH_OUT));

            MappedByteBuffer mbb = randomAccessFile.getChannel().map(READ_ONLY, 0, randomAccessFile.length());
            int size = (int) randomAccessFile.length() - 1;

            byte[] buffer = new byte[64000];
            int position = 0, length = 0;

            for (int i = size - 1; i > -1; --i) {
                byte b = mbb.get(i);
                if (b > 32 || b < 0) {
                    position = i;
                    ++length;
                } else if (length > 0) {
                    mbb.position(position);
                    mbb.get(buffer, 0, length);

                    os.write(buffer, 0, length);
                    os.write(SEPARATOR);
                    length = 0;
                }
            }

            if (length > 0) {
                mbb.position(position);
                mbb.get(buffer, 0, length);
                os.write(buffer, 0, length);
            }

            os.flush();


            long timeFinish = System.currentTimeMillis();

            System.out.print("Время: ");
            System.out.print((timeFinish - timeStart) / 1000d);
            System.out.println(" сек.");
        } finally {
            closeResource(randomAccessFile, os);
        }
    }

    public static void closeResource(AutoCloseable... resources) {
        for (AutoCloseable resource : resources) {
            if (resource != null) {
                try { resource.close(); } catch (Exception e) {}
            }
        }
    }

    public static void closeResource(Closeable... resources) {
        for (Closeable resource : resources) {
            if (resource != null) {
                try { resource.close(); } catch (Exception e) {}
            }
        }
    }
}

package textparse;

import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import static java.nio.channels.FileChannel.MapMode.READ_ONLY;

public class TextParse {
    
    private static final String
            PATH_SRC = "C:\\Documents and Settings\\User\\Рабочий стол\\src.txt",
            PATH_OUT = "C:\\Documents and Settings\\User\\Рабочий стол\\out.txt";
    private static final byte SEPARATOR[] = {0xD, 0xA};
    
    public static void main(String[] args) throws FileNotFoundException, IOException {
        long timeStart = System.currentTimeMillis();
        
        RandomAccessFile randomAccessFile = null;
        BufferedOutputStream os = null;
        try {
            randomAccessFile = new RandomAccessFile(PATH_SRC, "r");
            os = new BufferedOutputStream(new FileOutputStream(PATH_OUT));
            MappedByteBuffer mbb = randomAccessFile.getChannel().map(READ_ONLY, 0, randomAccessFile.length());
            
            byte[] buffer = new byte[64000];
            int position = 0, length = 0;
            
            for (int i = (int) (randomAccessFile.length() - 1); i > -1; --i) {
                byte b = mbb.get(i);
                if (b > 32 || b < 0) {
                    position = i;
                    ++length;
                } else if (length > 0) {
                    mbb.position(position);
                    mbb.get(buffer, 0, length);
                    os.write(buffer, 0, length);
                    os.write(SEPARATOR);
                    length = 0;
                }
            }
            
            if (length > 0) {
                mbb.position(position);
                mbb.get(buffer, 0, length);
                os.write(buffer, 0, length);
            }
            
            os.flush();
            
            
            long timeFinish = System.currentTimeMillis();
            
            System.out.print("Время: ");
            System.out.print((timeFinish - timeStart) / 1000d);
            System.out.println(" сек.");
        } finally {
            closeResource(randomAccessFile, os);
        }
    }
    
    public static void closeResource(AutoCloseable... resources) {
        for (AutoCloseable resource : resources) {
            if (resource != null) {
                try { resource.close(); } catch (Exception e) {}
            }
        }
    }
    
    public static void closeResource(Closeable... resources) {
        for (Closeable resource : resources) {
            if (resource != null) {
                try { resource.close(); } catch (Exception e) {}
            }
        }
    }
}