Anyone got codes for the ff.?

Frequency count

Stack and queue

Conversion of infix to postfix using stack

binary search tree

Anyone? my prof asked us to search for the ff and i thought this would be the best site with the best codes. thanks

public class DaniWebHelper {

   public static void main(String[] args) {

      String[] questions = {
            "Frequency count",
            "Stack and queue",
            "Conversion of infix to postfix using stack",
            "binary search tree"
      for (String q : questions) {
         String url = "";
         System.out.println("Answer to \"" + q +
               "\":\n\t- Open a browser and type following in URL:\n\t  "
               + url.replace("QQQ", q.replace(' ', '+'))
               + "\n\t- Now press enter!");