JAVA NIO Scatter&Gather机制(二)

BASIC

• NIO Channel中的scatter和gather机制
• scatter 从channel中读出写入到多个buffer中
• gather 从多个buffer中写入到一个一个channel
• transferFrom() & transferTo()
• 条件：一个channel是FileChannel
• 用于把数据从一个channel传到另一个channel

package nio_file;/**
 * @author: create by liubh

 * @date:2020/2/9
 */

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

/**
 * @author: create by liubh
 * @email [e-mail]
 * @date:2020/2/9
 */

/**
 * NIO Channel中的scatter和gather机制
 * scatter 从channel中读出写入到多个buffer中
 * gather  从多个buffer中写入到一个一个channel
 */
public class ScatterAndGather {
    public static void main(String[] args) throws IOException {
        RandomAccessFile file = new RandomAccessFile("/test.txt","rw");
        FileChannel channel = file.getChannel();
        String msg = "Hello,dear Kingx.\r\n" +
                "Don't\r\n leave me alone";
        String[] s = msg.split("\r\n",2);
        ByteBuffer head = ByteBuffer.allocate(s[0].length());
        ByteBuffer body = ByteBuffer.allocate(s[1].length());

        ByteBuffer[] buffers = {head,body};
        channel.write(buffers);
        
        /**
         * transferFrom() & transferTo()
         * 条件：一个channel是FileChannel
         * 用于把数据从一个channel传到另一个channel
         */
        RandomAccessFile file1 = new RandomAccessFile("/test1.txt","rw");
        RandomAccessFile file2 = new RandomAccessFile("/test2.txt","rw");
        FileChannel channel1 = file1.getChannel();
        FileChannel channel2 = file2.getChannel();
        long position = 0;
        long count    = channel2.size();
        channel1.transferFrom(channel2,position,count);
    }
}