HttpURLConnection继承了URLConnection，因此也可用于向指定网站发送GET请求、POST请求，而且它在URLConnection基础上提供了如下便捷方法：

实现多线程下载的步骤：

下面用一个示例来示范使用HttpURLConnection实现多线程下载。此代码来源疯狂讲义一书，该代码主要思路：在Activity中点击按钮,调用DownUtil的download()方法，在download()中启动四个线程去下载资源，每个线程负责下载自己的那部分资源，代码如下：

Activity：

package com.home.activity;import java.util.Timer;import java.util.TimerTask;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;import android.widget.ProgressBar;import com.home.multithreaddown.R;import com.home.util.DownUtil;public class MultiThreadDownActivity extends Activity {	private EditText urlText;	private EditText targetText;	private Button downBtn;	private ProgressBar bar;	private DownUtil downUtil;	private int mDownStatus;	private Handler handler;	@Override	protected void onCreate(Bundle savedInstanceState) {		super.onCreate(savedInstanceState);		setContentView(R.layout.main);		// 获取界面中控件		targetText = (EditText) findViewById(R.id.main_et_name);		urlText = (EditText) findViewById(R.id.main_et_url);		downBtn = (Button) findViewById(R.id.main_btn_download);		bar = (ProgressBar) findViewById(R.id.main_progressBar);		// 创建一个Handler对象		handler = new Handler() {			public void handleMessage(Message msg) {				if (msg.what == 0x123) {					bar.setProgress(mDownStatus);				}			}		};		downBtn.setOnClickListener(new OnClickListener() {			@Override			public void onClick(View v) {				// 初始化DownUtil对象				downUtil = new DownUtil(urlText.getText().toString(),						targetText.getText().toString(), 4);				try {					// 开始下载					downUtil.download();				} catch (Exception e) {					e.printStackTrace();				}				// 定义每秒调度获取一次系统的完成进度				final Timer timer = new Timer();				timer.schedule(new TimerTask() {					public void run() {						// 获取下载任务的完成比率						double completeRate = downUtil.getCompleteRate();						mDownStatus = (int) (completeRate * 100);						// 发送消息通知界面更新进度条						handler.sendEmptyMessage(0x123);						// 下载完成后取消任务调度						if (mDownStatus >= 100) {							timer.cancel();						}					}				}, 0, 100);			}		});	}}

下载的工具类（DownUtil）：

package com.home.util;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;public class DownUtil {	// 定义下载资源的路径	private String path;	// 指定所下载的文件的保存位置	private String targetFile;	// 定义需要使用多少线程下载资源	private int threadNum;	// 定义下载的文件的总大小	private int fileSize;	// 定义下载的线程对象	private DownloadThread[] threads;	public DownUtil(String path, String targetFile, int threadNum) {		this.path = path;		this.threadNum = threadNum;		// 初始化threads数组		threads = new DownloadThread[threadNum];		this.targetFile = targetFile;	}	public void download() throws Exception {		URL url = new URL(path);		HttpURLConnection conn = (HttpURLConnection) url.openConnection();		conn.setConnectTimeout(5 * 1000);		conn.setRequestMethod("GET");		conn.setRequestProperty(				"Accept",				"image/gif,image/jpeg,image/pjpeg,application/x-shockwaveflash,application/x-ms-xbap,application/xaml+xml,application/vnd.ms-xpsdocument,application/x-ms-application,application/vnd.ms-excel,application/vnd.ms-powerpoint,application/msword,*/*");		conn.setRequestProperty("Accept-Language", "zh-CN");		conn.setRequestProperty("Charset", "UTF-8");		conn.setRequestProperty(				"User-Agent",				"Mozilla/4.0(compatible;MSIE7.0;Windows NT 5.2;Trident/4.0;.NET CLR 1.1.4322;.NET CLR 2.0.50727;.NET CLR 3.0.04506.30;.NET CLR 3.0.4506.2152;.NET CLR 3.5.30729)");		conn.setRequestProperty("Connection", "Keep-Alive");		// 得到文件大小		fileSize = conn.getContentLength();		conn.disconnect();		int currentPartSize = fileSize / threadNum + 1;		RandomAccessFile file = new RandomAccessFile(targetFile, "rw");		// 设置本地文件的大小		file.setLength(fileSize);		file.close();		for (int i = 0; i < threadNum; i++) {			// 计算每条线程的下载的开始位置			int startPos = i * currentPartSize;			// 每个线程使用一个RandomAccessFile进行下载			RandomAccessFile currentPart = new RandomAccessFile(targetFile,					"rw");			// 定位该线程的下载位置			currentPart.seek(startPos);			// 创建下载线程			threads[i] = new DownloadThread(startPos, currentPartSize,					currentPart);			// 启动下载线程			threads[i].start();		}	}	/**	 * 获取下载完成的百分比	 * 	 * @return	 */	public double getCompleteRate() {		// 统计多条线程已经下载的总大小		int sumSize = 0;		for (int i = 0; i < threadNum; i++) {			sumSize += threads[i].length;		}		// 返回已经完成的百分比		return sumSize * 1.0 / fileSize;	}	private class DownloadThread extends Thread {		// 当前线程的下载位置		private int startPos;		// 定义当前线程负责下载的文件大小		private int currentPartSize;		// 当前线程需要下载的文件块		private RandomAccessFile currentPart;		// 定义该线程已下载的字节数		private int length = 0;		public DownloadThread(int startPos, int currentPartSize,				RandomAccessFile currentPart) {			this.startPos = startPos;			this.currentPartSize = currentPartSize;			this.currentPart = currentPart;		}		public void run() {			try {				URL url = new URL(path);				HttpURLConnection conn = (HttpURLConnection) url						.openConnection();				conn.setConnectTimeout(5 * 1000);				conn.setRequestMethod("GET");				conn.setRequestProperty(						"Accept",						"image/gif,image/jpeg,image/pjpeg,application/x-shockwaveflash,application/x-ms-xbap,application/xaml+xml,application/vnd.ms-xpsdocument,application/x-ms-application,application/vnd.ms-excel,application/vnd.ms-powerpoint,application/msword,*/*");				conn.setRequestProperty("Accept-Language", "zh-CN");				conn.setRequestProperty("Charset", "UTF-8");				InputStream is = conn.getInputStream();				// 跳过startPos个字符，表明该线程只下载自己负责那部分文件				is.skip(startPos);				byte[] by = new byte[1024];				int hasRead = 0;				// 读取网络数据，并写入本地文件				while (length < currentPartSize						&& (hasRead = is.read(by)) != -1) {					currentPart.write(by, 0, hasRead);					// 累计该线程下载的总大小					length += hasRead;				}				currentPart.close();				is.close();			} catch (Exception e) {				e.printStackTrace();			}		}	}}

Activity布局XML：

权限：