Java Help Please:( It is not working

/*
 *Write a Java program/class which creates an array with 100 random letters *using characters from ‘A’ to ‘Z’, displays the array in a 10x10 format, and displays *counts of the number of each of the random letters created. 
 */
package countlettersinarray;

public class CountLettersInArray {

    public static void main(String[] args) {
        char[] chars = createArray();

//Display Array
        System.out.println("The lowercase are: ");
        displayArray(chars);

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

//Display counts
        System.out.println();
        System.out.println("The occurrences of each letter are: ");
        displayCounts(counts);
    }

    /**
     * Create and array of
     */

    public static char[] createArray() {

        //Declare an array of characters and creaate it
        char[] chars = new char[100];
        //Create lowercase letters randomly and assign them to the array
        for (int i = 0; i < chars.length; i++) {
            chars[i] = RandomCharacter.getRandomLowerCaseLetter();
        }
        //Return the array
        return chars;
    }

    /**
     * Display the array of characters
     *
     * @param chars
     */
    public static void displayArray(char[] chars) {
        for (int i = 0; i < chars.length; i++) {
            if ((i + 1) % 20 == 0) {
                System.out.println(chars[i]);
            } else {
                System.out.println(chars[i] + " ");
            }
        }
    }

    /**
     * Count the occurrences of each letter
     */
    public static int[] countLetters(char[] chars) {
        //Declare and create and 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 ((i + 1) % 10 == 0) {
                System.out.println(counts[i] + " " + (char) (i + 'a'));
            } else {
                System.out.print(counts[i] + " " + (char) (i + 'a') + " ");
            }
        }
    }
}
}
}