Java NIO开始支持scatter/gather，scatter/gather用于描述从Channel（译者注：Channel在中文经常翻译为通道）中读取或者写入到Channel的操作。
分散（scatter）从Channel中读取是指在读操作时将读取的数据写入多个buffer中。因此，Channel将从Channel中读取的数据“分散（scatter）”到多个Buffer中。
聚集（gather）写入Channel是指在写操作时将多个buffer的数据写入同一个Channel，因此，Channel 将多个Buffer中的数据“聚集（gather）”后发送到Channel。

scatter / gather经常用于需要将传输的数据分开处理的场合，例如传输一个由消息头和消息体组成的消息，你可能会将消息体和消息头分散到不同的buffer中，这样你可以方便的处理消息头和消息体。

Scatter/Gather操作查看下图：

代码清单：

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.GatheringByteChannel;
import java.nio.channels.ScatteringByteChannel;

public class ScatterAndGather {

static String headers = "header:13byte ";
static String bodys = "body:Scattering and Gathering example";

public static void main(String[] args) {
    gather();
    scatter();
}

public static void scatter() {

    ByteBuffer header = ByteBuffer.allocate(13);
    ByteBuffer body = ByteBuffer.allocate(100);

    ByteBuffer[] bufferArray = { header, body };

    ScatteringByteChannel channel = getChannel();

    try {
        channel.read(bufferArray);
    } catch (IOException e) {
        e.printStackTrace();
    }

    header.rewind();
    body.rewind();

    String headerStr = convertBufferToString(header);
    String bodyStr = convertBufferToString(body);
    System.out.println(headerStr);
    System.out.println(bodyStr);

}

public static void gather() {
    ByteBuffer header = ByteBuffer.allocate(14);
    ByteBuffer body = ByteBuffer.allocate(100);

    header.put(headers.getBytes());
    body.put(bodys.getBytes());

    GatheringByteChannel channel = getChannel();

    try {
        header.flip();
        body.flip();
        channel.write(new ByteBuffer[] { header, body });
    } catch (IOException e) {
        e.printStackTrace();
    }

}

public static FileChannel getChannel() {

    RandomAccessFile raf = null;
    try {
        raf = new RandomAccessFile("e:/sg.txt", "rw");
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

    return raf.getChannel();
}

public static String convertBufferToString(ByteBuffer buffer) {
    StringBuilder sb = new StringBuilder();
    while (buffer.remaining() != 0) {
        sb.append((char) buffer.get());
    }
    return sb.toString();
}

}