RecursionAssignment1.java

public class RecursionAssignment1 {
    public static void main(String[] args) {
        int[] arr = new int[] {
                18,
                21,
                22,
                8,
                31,
                1,
                5
        };

        System.out.println(getLargestNumber(arr, arr.length - 1));
        System.out.println(getGreatestCommonDivisor(24, 54));
        System.out.println(reverseString("Mustangs"));
    }

    public static int getLargestNumber(int[] arr, int index) {
        if (index == 0) {
            return arr[index];
        }

        return Math.max(arr[index], getLargestNumber(arr, index - 1));
    }

    public static int getGreatestCommonDivisor(int a, int b) {
        if (b == 0) {
            return a;
        }

        return getGreatestCommonDivisor(b, a % b);
    }

    public static String reverseString(String str) {
        if (str.isEmpty()) {
            return str;
        }

        return reverseString(str.substring(1)) + str.charAt(0);
    }
}