counting occurances in a method

      // generates random characters
public void add (char fromChar, char toChar){      
int range = toChar - fromChar;
int seed = fromChar * toChar;
Random rr = new Random(seed);
for (int i = 0; i < charArray; ++i) {
    char randomChar = (char)(fromChar + rr.nextInt(range));
    System.out.println("Next character: " + randomChar);
}   
 
public int[] countLetters(){ //method im working on
        int [] countLetters =new int[26];
       char current;
       
for(int i=0; i<countletters.length;>   current=.charAt(i);
    if (current >= 'a' && current <= 'z'){
       countLetters[current-'a']++;
   }
}
        return null;   
    }