Write recursive methods for the following operations: • removeDup(String s): takes string s and returns another string r constructed from s after removing all duplicates. For example, when s = "pineapples", r will be "pineals". • intersection(String s1, String s2): takes two duplicate-free strings and returns the string consisting of all letters that appear in both s1 and s2. • union(String s1, String s2): takes two duplicate-free strings and returns the string consisting of all letters that appear in either s1 or s2. • difference(String s1, String s2): takes two duplicate-free strings and returns the string consisting of all letters that appear only in s1. For example, when s1 = "aples" and s2 = "pears", intersection(s1, s2) will return "apes", union(s1, s2) will "aplesr", and difference(s1, s2) "l". Calling method removeDup() is not allowed in intersection(s1, s2) , union(s1, s2) or difference(s1, s2) method. Your program should check strings are duplicate free before they are passed to those methods. Note that all the methods must be recursive and should not contain any loops. Your main method in this program should demonstrate the use of your methods with a menu for the user to pick the method to try and enter their strings for use in the method. The strings should be entered after the user picks their choice of either remove duplicates, union, intersection, or difference so they can test each method with different strings. Also, the main method should print the strings that are returned by each method since the methods themselves shouldn’t print anything.

Write recursive methods for the following operations: • removeDup(String s): takes string s and returns another string r constructed from s after removing all duplicates. For example, when s = "pineapples", r will be "pineals". • intersection(String s1, String s2): takes two duplicate-free strings and returns the string consisting of all letters that appear in both s1 and s2. • union(String s1, String s2): takes two duplicate-free strings and returns the string consisting of all letters that appear in either s1 or s2. • difference(String s1, String s2): takes two duplicate-free strings and returns the string consisting of all letters that appear only in s1. For example, when s1 = "aples" and s2 = "pears", intersection(s1, s2) will return "apes", union(s1, s2) will "aplesr", and difference(s1, s2) "l". Calling method removeDup() is not allowed in intersection(s1, s2) , union(s1, s2) or difference(s1, s2) method. Your program should check strings are duplicate free before they are passed to those methods. Note that all the methods must be recursive and should not contain any loops. Your main method in this program should demonstrate the use of your methods with a menu for the user to pick the method to try and enter their strings for use in the method. The strings should be entered after the user picks their choice of either remove duplicates, union, intersection, or difference so they can test each method with different strings. Also, the main method should print the strings that are returned by each method since the methods themselves shouldn’t print anything.