Java 网络爬虫获取页面源代码

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class WebPageSource {
    public static void main(String args[]){    
        URL url;
        int responsecode;
        HttpURLConnection urlConnection;
        BufferedReader reader;
        String line;
        try{
            //生成一个URL对象，要获取源代码的网页地址为：http://www.sina.com.cn
            url=new URL("http://www.sina.com.cn");
            //打开URL
            urlConnection = (HttpURLConnection)url.openConnection();
            //获取服务器响应代码
            responsecode=urlConnection.getResponseCode();
            if(responsecode==200){
                //得到输入流，即获得了网页的内容 
                reader=new BufferedReader(new InputStreamReader(urlConnection.getInputStream(),"UTF-8"));
                while((line=reader.readLine())!=null){
                    System.out.println(line);
                }
            }
            else{
                System.out.println("获取不到网页的源码，服务器响应代码为："+responsecode);
            }
        }
        catch(Exception e){
            System.out.println("获取不到网页的源码,出现异常："+e);
        }
    }
}