java正则表达式简单使用和网页爬虫的制作代码

String regex="\\.";

String regex="[0-9]{5,}";

String   newstr=str.replaceAll(regex,"#");

Matcher  m=p.matcher(String str);

while(m.find())

{

System.out.println(m.group());

}

从网络中获取邮箱地址
*/
import java.io.*;
import java.util.regex.*;
import java.net.*;
class  MailTest
{
 public static void main(String[] args) throws Exception
 {
  getMailAddr();
 }

 public static void getMailAddr()throws Exception
 {
  URL url=new URL("http://bbs.jb51.net/topics/390148495");
  URLConnection con=url.openConnection();

  BufferedReader bufIn=new BufferedReader(new InputStreamReader(con.getInputStream()));
  BufferedWriter bufw=new BufferedWriter(new FileWriter(new File("e://mailaddress.txt")));
  String str=null;
  String regex="[a-zA-Z0-9_]{6,12}@[a-zA-Z0-9]+(\\.[a-zA-Z]+)+";

  Pattern p=Pattern.compile(regex);
  while((str=bufIn.readLine())!=null)
  {
   Matcher m=p.matcher(str);
   while(m.find())
   {
    String ss=m.group();
    bufw.write(ss,0,ss.length());
    bufw.newLine();
    bufw.flush();
   }
  }

 }
}