用java怎么实现统计一英文文档里各个英语字母的个数及所占百分比

import java。io。BufferedReader;import java。io。FileReader;import java。io。IOException;public class Test {\x05public static void main(String[] args) throws IOException {\x05\x05\x05\x05StringBuilder sb = new StringBuilder();\x05\x05\x05\x05String file = "words。txt";\x05\x05BufferedReader bf = new BufferedReader(new FileReader(file));\x05\x05\x05\x05String content = null;\x05\x05\x05\x05while((content = bf。readLine()) != null){\x05\x05\x05sb。append(content。trim());\x05\x05}//如果只统计小写,就传递'a','z'进去\x05\x05\x05\x05countCracts(sb。toString(),'a','z');\x05\x05System。out。println();//大写,'A'-'Z'\x05\x05countCracts(sb。toString(),'A','Z');\x05}\x05private static void countCracts(String str,char start,char end) {\x05\x05for(char a = start; a