java统计字符串中指定元素出现次数方法

package com.zuidaima.util.string; import java.io.*; public class CountString {    public static int count(String filename, String target)   throws FileNotFoundException, IOException {   FileReader fr = new FileReader(filename);   BufferedReader br = new BufferedReader(fr);   StringBuilder strb = new StringBuilder();   while (true) {   String line = br.readLine();   if (line == null) {    break;   }   strb.append(line);   }   String result = strb.toString();   int count = 0;   int index = 0;   while (true) {   index = result.indexOf(target, index + 1);   if (index > 0) {    count++;   } else {    break;   }   }   br.close();   return count;  }    public static void main(String[] args) {   try {   System.out.println(count("D://zuidaima.txt", "a"));   } catch (FileNotFoundException e) {   e.printStackTrace();   } catch (IOException e) {   e.printStackTrace();   }  }   }