Задача 1

 public static void main(String[] args) {

        int[] arr = {4, 5, 3, 2, 5, 5, 6};

        int max = Integer.MIN_VALUE;

        for (int i = 0; i < arr.length; i++) {
            if (arr[i] > max) {
                max = arr[i];
            }
        }

        int[] B = new int[max + 1];

        for (int i = 0; i < arr.length; i++) {
            B[arr[i]]++;
        }
        for (int i = 0; i <= max; i++) {
            if (B[i] > 1) {

              System.out.println("The most common element in array is: " + "(" + i + ")");
              System.out.println("How many times the most common element is repeated: " + "(" + B[i] + ")");
            }
        }
    }
}