利用搜索引擎实现命令行计算器

//利用搜索引擎实现命令行计算器
import java.io.*;
import java.net.*;
/**
* 54powerman
* http://54powerman.blog.sohu.com
**/
public class Cal
{
 final static String defaultCharset=System.getProperty("file.encoding");
 public static void main(String args[])
 {
  String express=null;
  if(args.length<1)
  {
   System.out.println("[Usage]: java Cal [expressions]");
   return;
  }
  express=args[0].trim();
  String url=null;
  try{
   url="http://www.baidu.com/s?wd="+java.net.URLEncoder.encode(express,defaultCharset)+"&cl=3";
  }
  catch(UnsupportedEncodingException e){}
  String result=OpenUrl(url,"");
  int start=result.indexOf("http://img.baidu.com/img/jsq.gif");
  if(start>0){
   int end=0;
   start=result.indexOf("<b>"+express,start);
   start=result.indexOf("=",start)+1;
   end=result.indexOf("</b>",start);
   result=result.substring(start,end).trim();
  }
  if(result.indexOf("/n")>0)
  {
   System.out.println("express error.");
  }
  else
  {
   System.out.print(result);
  }
 }
 public static String OpenUrl(String urlString,String postParam) {
   StringBuffer document = new StringBuffer();
   try {
  URL url = new URL(urlString);
  URLConnection conn = url.openConnection();
  if(!postParam.trim().equals("")){
   conn.setDoOutput(true);
   OutputStreamWriter out = new OutputStreamWriter(conn.getOutputStream(), defaultCharset);
   out.write(postParam);
   out.flush();
   out.close();
  }
  BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
  String line = null;
  while ( (line = reader.readLine()) != null) {
    document.append(line + "/n");
  }
  reader.close();
   }
   catch (MalformedURLException e) {
  System.out.println("Unable to connect to URL: " + urlString);
   }
   catch (IOException e) {
  System.out.println("IOException when connecting to URL: " + urlString);
   }
   return document.toString();
  }

}