import java.io.IOException;

import java.io.RandomAccessFile;

import java.nio.channels.FileChannel;

import java.nio.MappedByteBuffer;

public class MappedByteBufferDemo{

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

if(args.length != 1){

System.err.println("usage: java MappedByteBufferDemo file");

return;

}

RandomAccessFile raf = new RandomAccessFile(args[0], "rw");

FileChannel fc = raf.getChannel();

long size = fc.size();

System.out.println("Size: " + size);

MappedByteBuffer mbb = fc.map(FileChannel.MapMode.PRIVATE, 0, size);

while(mbb.hasRemaining()){

System.out.print((char)mbb.get());

}

System.out.println();

System.out.println();

// reverse the file content.

for(int i=0; i<mbb.limit()/2; i++){

int mirrorIndex = mbb.limit()-1-i;

byte b1 = mbb.get(i);

byte b2 = mbb.get(mirrorIndex);

mbb.put(i, b2);

mbb.put(mirrorIndex, b1);

}

// read the buffer content again.

mbb.flip();

while(mbb.hasRemaining()){

System.out.print((char)mbb.get());

}

fc.close();

}

}