Java多线程下载文件实例详解

Java多线程下载文件实例详解

本文实例为大家分享了java多线程下载文件的具体代码，供大家参考，具体内容如下

import java.io.File;

import java.io.InputStream;

import java.io.RandomAccessFile;

import java.net.HttpURLCYsadMQonnection;

import java.net.URL;

public class MulThreadDownload {

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

String path = "http://192.168.1.100:8080/Hello/Big.exe";

new MulThreadDownload().download(path, 3);

}

/**

* 下载文件

*

* @param path

* 网络文件路径

* @param threadSize

* 线程数

* @throws Exception

*/

private void download(String path, int threadSize) throws Exception {

URL url = new URL(path);

HttpURLConnection connection = (HttpURLConnection) url.openConnection();

connection.setRequestMethod("GET");

connection.setConnectTimeout(5000);

if (connection.getResponseCode() == 200) {

int length = connection.getContentLength();// 获取网络文件长度

File file = new File(getFileName(path));

// 在本地生成一个长度与网络文件相同的文件

RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");

accessFile.setLength(length);

accessFile.close();

// 计算每条线程负责下载的数据量

int block = length % threadSize == 0 ? length / threadSize : length

/ threadSize + 1;

for (int threadId = 0; threadId < threadSize; threadId++) {

http:// new DownloadThread(threadId, block, url, file).start();

}

} else {

System.out.println("download fail");

}

}

private class DownloadThread extends Thread {

private int threadId;

private int block;

private URL url;

private File file;

public DownloadThread(int threadId, int block, URL url, File file) {

this.threadId = threadId;

this.block = block;

this.url = url;

this.file = file;

}

@Override

public void run() {

int start = threadId * block; // 计算该线程从网络文件什么位置开始下YsadMQ载

int end = (threadId + 1) * block - 1; // 计算下载到网络文件什么位置结束

try {

RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");

accessFile.seek(start); //从start开始

HttpURLConnection connection = (HttpURLConnection) url

.openConnection();

connection.setRequestMethod("GET");

connection.setConnectTimeout(5000);

//设置获取资源数据的范围，从start到end

connection.setRequestProperty("Range", "bytes=" + start + "-"

+ end);

//注意多线程下载状态码是 206 不是200

if (connection.getResponseCode() == 206) {

InputStream inputStream = connection.getInputStream();

byte[] buffer = new byte[1024];

int len = 0;

while ((len = inputStream.read(buffer)) != -1) {

accessFile.write(buffer, 0, len);

}

accessFile.close();

inputStream.close();

}

System.out.println("第" + (threadId + 1) + "条线程已经下载完成");

} catch (Exception e) {

e.printStackTrace();

}

}

}

/**

* 获取文件名称

*

* @param path

* 网络文件路径

* @return

*/

private String getFileName(String path) {

return path.substring(path.lastIndexOf("/") + 1);

}

}

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