java获取字母出现的次数

public Count{

public static void main(String[] args) {String str = "ADFGZXCVASDFXCVDF";
countLetters(str );
}

  public static void countLetters(String str){

if (str == null || str.length == 0){

   return;

}
str = str.toLowerCase();HashMap<Character, Integer> map = new HashMap<Character, Integer>();for(int i = 0; i<str.length(); i++){char c = str.charAt(i);if (map.containsKey(c)) {map.put(c, map.get(c)+1);}else{map.put(c, 1);}}Iterator<Character> itr = map.keySet().iterator();while(itr.hasNext()){char c = itr.next();System.out.println(c + "("+map.get(c).intValue()+")");}

}   }

}