--> 默认最多50个线程 同一文件下载失败延迟超过30秒就结束下载

--> 下载5分钟超时时间，假设5分钟内未下载完就结束下载

--> 依赖 commons-httpclient 与 commons-io 包

package com.leunpha;import org.apache.commons.httpclient.HttpClient;import org.apache.commons.httpclient.methods.GetMethod;import org.apache.commons.httpclient.params.HttpClientParams;import org.apache.commons.io.IOUtils;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import java.io.*;import java.lang.reflect.Method;import java.nio.MappedByteBuffer;import java.nio.channels.FileChannel;import java.security.AccessController;import java.security.PrivilegedAction;import java.util.Observable;import java.util.Timer;import java.util.TimerTask;import java.util.concurrent.CountDownLatch;import java.util.concurrent.TimeUnit;import java.util.concurrent.atomic.AtomicInteger;import java.util.concurrent.atomic.AtomicLong;import java.util.zip.ZipFile;/** * User: zhoujingjie * Date: 14-4-18 * Time: 下午12:52 */public class Downloader extends Observable {    protected String url, savePath;             //下载地址与保存路径    protected FileChannel channel;              //保存文件的通道    protected long size, perSize;              //文件大小与每一个小文件的大小    protected volatile long downloaded;       // 已下载的    protected int connectCount;                 //连接数    protected Connection[] connections;         //连接对象    protected boolean isSupportRange;         //是否支持断点下载    protected long timeout;                     //超时    protected boolean exists;                   //是否存在    private RandomAccessFile randomAccessFile;    protected volatile boolean stop;            //停止    private static volatile  boolean exception; //是否异常    private AtomicLong prevDownloaded = new AtomicLong(0); //上一次的下载结果    private static Log log = LogFactory.getLog(Downloader.class);    private AtomicInteger loseNum = new AtomicInteger(0);    private int maxThread;    public Downloader(String url, String savePath) throws IOException {        //超时一小时        this(url, savePath, 1000 * 60*5,50);    }    public Downloader(String url, String savePath, long timeout,int maxThread) throws FileNotFoundException {        this.timeout = timeout;        this.url = url;        this.maxThread = maxThread;        File file = new File(savePath);        if (!file.exists()) file.mkdirs();        this.savePath= file.getAbsolutePath() + "/" + url.substring(url.lastIndexOf("/"));        exists = new File(this.savePath).exists();        if(!exists){            randomAccessFile=   new RandomAccessFile(this.savePath+".temp", "rw");            channel =randomAccessFile.getChannel();        }    }    public GetMethod method(long start, long end) throws IOException {        GetMethod method = new GetMethod(Downloader.this.url);        method.setRequestHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/30.0.1599.101 Safari/537.36");        if (end > 0) {            method.setRequestHeader("Range", "bytes=" + start + "-" + (end - 1));        } else {            method.setRequestHeader("Range", "bytes=" + start + "-");        }        HttpClientParams clientParams = new HttpClientParams();        //5秒超时        clientParams.setConnectionManagerTimeout(5000);        HttpClient client = new HttpClient(clientParams);        client.executeMethod(method);        int statusCode = method.getStatusCode();        if (statusCode >= 200 && statusCode < 300) {            isSupportRange = (statusCode == 206) ? true : false;        }        return method;    }    public void init() throws IOException {        size = method(0, -1).getResponseContentLength();        if (isSupportRange) {            if (size < 4 * 1024 * 1024) {  //假设小于4M                connectCount = 1;            } else if (size < 10 * 1024 * 1024) { //假设文件小于10M 则两个连接                connectCount = 2;            } else if (size < 30 * 1024 * 1024) { //假设文件小于80M 则使用6个连接                connectCount = 3;            } else if (size < 60 * 1024 * 1024) {          //假设小于60M 则使用10个连接                connectCount = 4;            } else {                //否则为10个连接                connectCount = 5;            }        } else {            connectCount = 1;        }        log.debug(String.format("%s size:%s connectCount:%s", this.url, this.size, this.connectCount));        perSize = size / connectCount;        connections = new Connection[connectCount];        long offset = 0;        for (int i = 0; i < connectCount - 1; i++) {            connections[i] = new Connection(offset, offset + perSize);            offset += perSize;        }        connections[connectCount - 1] = new Connection(offset, size);    }    /**     * 强制释放内存映射     *     * @param mappedByteBuffer     */    static void unmapFileChannel(final MappedByteBuffer mappedByteBuffer) {        try {            if (mappedByteBuffer == null) {                return;            }            mappedByteBuffer.force();            AccessController.doPrivileged(new PrivilegedAction