How to get Html code using the Internet? Principle of obtaining Html code from the network

package cn.captain.html;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class htmlRequest {
		/**
		 * @param args
		 * @throws MalformedURLException 
		 */
		public static void main(String[] args) throws Exception
		{
			URL url = new URL("http://www.baidu.com/"); 
			HttpURLConnection conn = (HttpURLConnection)url.openConnection();
			conn.setRequestMethod("GET");
			conn.setConnectTimeout(5 * 1000);
			InputStream inStream =  conn.getInputStream();//通过输入流获取html数据	
			byte[] data = readInputStream(inStream);//得到html的二进制数据
			String html = new String(data);
			System.out.println(html);
		}
	   public static byte[] readInputStream(InputStream instream) throws Exception
	    {
			ByteArrayOutputStream outStream = new ByteArrayOutputStream();
			byte[]  buffer = new byte[1204];
			int len = 0;
			while ((len = instream.read(buffer)) != -1)
			{
				outStream.write(buffer,0,len);
			}
			instream.close();
			return outStream.toByteArray();     	
		}

	}