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：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical" >

    <LinearLayout

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:orientation="horizontal" >

        <TextView

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="输入url:" />

        <EditText

            android:id="@+id/main_et_url"

            android:layout_width="match_parent"

            android:layout_height="wrap_content" />

    </LinearLayout>

    <LinearLayout

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:orientation="horizontal" >

        <TextView

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="输入保存的文件名:" />

        <EditText

            android:id="@+id/main_et_name"

            android:layout_width="match_parent"

            android:layout_height="wrap_content" />

    </LinearLayout>

    <Button

        android:id="@+id/main_btn_download"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="下载" />

    <ProgressBar

        android:id="@+id/main_progressBar"

        style="@android:style/Widget.ProgressBar.Horizontal"

        android:layout_width="match_parent"

        android:layout_height="wrap_content" />

</LinearLayout>

权限：

<!-- 在SD卡中创建与删除文件权限 -->

<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>

<!-- 向SD卡写入数据权限 -->

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

<!-- 授权访问网络 -->

<uses-permission android:name="android.permission.INTERNET"/>