public class Histogram2 {

  static String input = "zzzzabcdfdkkiiik";
//  static char[] charArray = new char[]{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k'};

  public static void main(String[] args) {
    char[][] matrix = new char[26][26];

    for (int i = 0; i < input.length(); i++) {
      char c = input.charAt(i);

      int index = c - 97;

      if (matrix[index][0] == 0) {
        matrix[index][0] = c;
        matrix[index][1] = '*';
      } else {
        for (int k = 1; k < input.length(); k++) {
          if (c != 0 && matrix[index][k] != '*') {
            matrix[index][k] = '*';
            c = 0;
          }
        }
      }
    }

    printMatrix(matrix);
  }

  private static void printMatrix(char[][] matrix) {
    System.out.println("Matrica je oblika:");
    for (int i = 0; i < matrix.length; i++) {
      if (matrix[i][0] != 0) {
        System.out.println();
        for (int j = 0; j < matrix.length; j++) {
          if (matrix[i][j] == 0) {
            System.out.print(" ");
          } else {
            System.out.print(matrix[i][j] + " ");
          }
        }
      }
    }
  }
}