NIO(四) - 分散(Scatter) 与聚集 (Gather)

最新推荐文章于 2024-07-06 09:46:05 发布

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本文详细介绍Java NIO中分散读取与聚集写入的概念及其实现方式，通过具体示例展示如何使用ByteBuffer与FileChannel进行高效数据处理。

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package com.xbb.demo;

import org.junit.Test;

import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

/**
 * 五 : 分散(Scatter) 与聚集 (Gather)
 *      分散读取(Scattering Reads) : 将通道中的数据分散到多个缓冲区中
 *      聚集写入(Gathering Writes) : 将多个缓冲区中的数据聚集到通道中
 *
 *      注意 : 按照缓冲区的顺序,从Channel中读取的数据今次将Buffer填满
 */
public class ScatterAndGatherDemo {

    /**
     * 分散读取
     */
    @Test
    public void scatterTest(){
        try(
            RandomAccessFile raf = new RandomAccessFile("/Users/riverjin/java_pro/nio/src/main/java/com/xbb/demo/ChannelDemo.java","rw");
            FileChannel rafChannel = raf.getChannel();
        ){
            ByteBuffer buf1 = ByteBuffer.allocate(100);
            ByteBuffer buf2 = ByteBuffer.allocate(10240);
            ByteBuffer[] bufs = {buf1,buf2};
            rafChannel.read(bufs);
            for (ByteBuffer buf: bufs) {
                buf.flip();
            }
            System.out.println(new String(bufs[0].array(),0,bufs[0].limit()));
            System.out.println(new String(bufs[1].array(),0,bufs[1].limit()));
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    /**
     * 聚集写入
     */
    @Test
    public void gatherTest(){
        try(
            RandomAccessFile rafR = new RandomAccessFile("/Users/riverjin/java_pro/nio/src/main/java/com/xbb/demo/ChannelDemo.java","rw");
            RandomAccessFile rafW = new RandomAccessFile("/Users/riverjin/java_pro/nio/src/main/java/com/xbb/demo/ChannelDemo2.java","rw");
            FileChannel rChannel = rafR.getChannel();
            FileChannel wChannel = rafW.getChannel();
        ){
            ByteBuffer buf1 = ByteBuffer.allocate(500);
            ByteBuffer buf2 = ByteBuffer.allocate(10240);
            ByteBuffer[] bufs = {buf1,buf2};
            rChannel.read(bufs);
            for (ByteBuffer buf : bufs) {
                buf.flip();
            }
            wChannel.write(bufs);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}