Please write a java program using only one main class with these 4 different function of recusive method. Thanks

Write a recursive method that computes x^n for a positive integer n using the following header:

public static double powerN(double x, int n){

//implement body

}

Write a recursive method that computes the following series using the following header:

S = 1 +1/ 2 + 1/3+ ...+1/ n

public static double harmonicSum(int n){ //implement body

}

Write a recursive method that displays an int value reversely on the console using the following header:

public static void reverseDisplay(int value){

//implement body

}

Write a recursive method that displays a string reversely on the console using the following header:

public static void reverseDisplay(String value){ //implement body