import java.io.*; import java.nio.*; import java.nio.channels.*; public class LargeMappedFiles {    static int length = 0x8FFFFFF; // 128 Mb    public static void main(String[] args) throws Exception {      MappedByteBuffer out =         new RandomAccessFile("test.dat", "rw").getChannel()        .map(FileChannel.MapMode.READ_WRITE, 0, length);      for(int i = 0; i < length; i++)        out.put((byte)'x');      System.out.println("Finished writing");      for(int i = length/2; i < length/2 + 6; i++)        System.out.print((char)out.get(i));    //read file    } } ///