Java Array count occurrences of letter in char array

public class Main {
  public static void main(String[] args) {
    char[] chars = "demoscomtesttest".toCharArray();

    // Count the occurrences of each letter
    int[] counts = countLetters(chars);

    System.out.println("The occurrences of each letter are:");
    displayCounts(counts);//from   w  w w .j a va  2  s.c  o  m
  }
  /** Count the occurrences of each letter */
  public static int[] countLetters(char[] chars) {
    // Declare and create an array of 26 int
    int[] counts = new int[26];

    // For each lowercase letter in the array, count it
    for (int i = 0; i < chars.length; i++)
      counts[chars[i] - 'a']++;

    return counts;
  }

  /** Display counts */
  public static void displayCounts(int[] counts) {
    for (int i = 0; i < counts.length; i++) {
      if(counts[i] > 0) {
        System.out.println((char)(i + 'a') +" " + counts[i] );  
      }      
    }
  }
}