import java.nio.channels.Channels;

import java.nio.channels.ScatteringByteChannel;

import java.nio.channels.GatheringByteChannel;

import java.nio.ByteBuffer;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

public class ScatterGatherChannel{

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

if(args.length!=2){

System.err.println("usage: java ScatterGatherChannel inputFile outputFile");

return;

}

ScatteringByteChannel readChannel = (ScatteringByteChannel) Channels.newChannel(new FileInputStream(args[0]));

ByteBuffer buffer1 = ByteBuffer.allocateDirect(5);

ByteBuffer buffer2 = ByteBuffer.allocateDirect(10);

ByteBuffer[] buffers = {buffer1, buffer2};

readChannel.read(buffers);

System.out.println("buffers' limit: " + buffer1.limit() + ", " + buffer2.limit());

// Need do flip operation.

buffer1.flip();

buffer2.flip();

// Inspect the contents of the buffer after reading.

while(buffer1.hasRemaining()){

System.out.println("buffer1 element at position " + buffer1.position() + " : " + buffer1.get());

}

System.out.println();

while(buffer2.hasRemaining()){

System.out.println("buffer2 element at position " + buffer2.position() + " : " + buffer2.get());

}

// prepare for writing operation.

buffer1.rewind();

buffer2.rewind();

GatheringByteChannel writeChannel = (GatheringByteChannel) Channels.newChannel(new FileOutputStream(args[1]));

buffers[0] = buffer2;

buffers[1] = buffer1;

writeChannel.write(buffers);

readChannel.close();

writeChannel.close();

}

}