写一个程序，从文件（c:\test.txt）中查出字符串”mobnet”出现的次数

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class TxtCount {

 /**
  * @param args
  */
 public static void main(String[] args) throws Exception {
  BufferedReader br = new BufferedReader(new FileReader("C:\\test.txt"));
  StringBuilder sb = new StringBuilder();
  while (true) {
   String str = br.readLine();
   if (str == null)
    break;
   sb.append(str);
  }
  Pattern p = Pattern.compile("mobnet");
  Matcher m = p.matcher(sb);
  int count = 0;
  while(m.find()) {
   count++;
  }
  System.out.println("mobnet一共出现了" + count + "次");
 }

}