Implement the following recursive methods (in java):

// Recursively determines if the substring of num with starting index i and ending index j is a palindrome

public static boolean recursiveIsPalindrome(String num, int i, int j)

{

// TO DO (A)

}

// Recursively calculates the nth fibonacci number

public static long recursiveFibonacci(int n)

{

// TO DO (B)

}

// Recursively calculates the GCD of a and b

public static int recursiveGCD(int a, int b)

{

// TO DO (C)

}

// Recursively calculates aⁿ

public static double recursivePowInt(double a, int n)

{

// TO DO (D)

}