Java内存映射文件实现多线程下载

Java NIO内存映射文件可以实现多线程下载首先，使用Firefox下载一个TomcatJava多线程：一道阿里面试题的分析与应对 http://www.linuxidc.com/Linux/2014-03/98715.htmJava多线程下载程序import java.io.FileNotFoundException;

import java.io.IOException;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;import java.nio.MappedByteBuffer;import java.nio.channels.FileChannel.MapMode; class Worker implements Runnable { //多线程下载的数量 private static int THREADS = 4; //每个线程下载开始的位置 private int startIndex; //每个线程下载内容的长度 private int length; //文件保存位置 private String localFile; //远程文件的流 InputStream in; private Worker（String urlFile, String localFile, int startIndex, int length） throws IOException { this.startIndex = startIndex; this.length = length; this.localFile = localFile; init（urlFile）; } /** * 主线程打开网络文件,先分割为指定的大小，然后开启多线程下载 */ public Worker（String urlFile, String localFile） throws IOException { this.localFile = localFile; int contentLength = init（urlFile）; int step = contentLength / THREADS; int index = 0; for （int i = 0; i < THREADS; i++） { if （i == 0） { this.startIndex = 0; this.length = step; new Thread（this）.start（）; } else if （i == THREADS - 1） { Worker worker = new Worker（urlFile, localFile, index, contentLength - index）; new Thread（worker）.start（）; } else { Worker worker = new Worker（urlFile, localFile, index, step）; new Thread（worker）.start（）; } index = index + step; } } private int init（String urlFile） throws IOException { URL url; url = new URL（urlFile）; HttpURLConnection connection = （HttpURLConnection） url.openConnection（）; connection.setConnectTimeout（5 * 1000）; connection.setRequestMethod（"GET"）; connection.setRequestProperty（"Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, " + "application/x-shockwave-flash, application/xaml+xml, " + "application/vnd.ms-xpsdocument, application/x-ms-xbap, " + "application/x-ms-application, application/vnd.ms-excel, " + "application/vnd.ms-powerpoint, application/msword, */*"）; connection.setRequestProperty（"Accept-Language", "zh-CN"）; connection.setRequestProperty（"Charset", "UTF-8"）; connection.setRequestProperty（"Connection", "Keep-Alive"）; InputStream in = connection.getInputStream（）; this.in = in; return connection.getContentLength（）; } @Override public void run（） { System.out.println（this）; try { RandomAccessFile localRandomFile = new RandomAccessFile（localFile, "rw"）; MappedByteBuffer buffer = localRandomFile.getChannel（）.map（MapMode.READ_WRITE, startIndex, length）; int i = 0; in.skip（startIndex）; while （i < length） { buffer.put（（byte） in.read（））; i++; } buffer.force（）; in.close（）; localRandomFile.close（）; } catch （FileNotFoundException e） { e.printStackTrace（）; } catch （IOException e） { e.printStackTrace（）; } } @Override public String toString（） { return "Worker [localFile=" + localFile + ", startIndex=" + startIndex + ", length=" + length + "]"; } public static void main（String[] args） throws IOException { new Worker（"http://mirrors.cnnic.cn/apache/tomcat/tomcat-7/v7.0.53/bin/apache-tomcat-7.0.53.zip", "tomcat.zip"）; }}比对下载的文件

Java1.5后的多线程框架 http://www.linuxidc.com/Linux/2014-02/96879.htmJava多线程和同步的理解 http://www.linuxidc.com/Linux/2013-12/93691.htmJava中两种实现多线程方式的对比分析 http://www.linuxidc.com/Linux/2013-12/93690.htmJava利用多线程计算目录数据大小 http://www.linuxidc.com/Linux/2013-09/90715.htmJava多线程向数据库写入数据 http://www.linuxidc.com/Linux/2013-09/90297.htm本文永久更新链接地址：http://www.linuxidc.com/Linux/2014-05/102201.htm