初学者指南：简单Java网络爬虫抓取并保存网页内容

package crawler;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
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;
        BufferedWriter writer;
        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(),"GBK"));
                writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(new File("d://test.txt"))));
                while((line=reader.readLine())!=null){