Lecture 17

Computer Science 252
Problem Solving with Java

Spring 2016, The College of Saint Rose

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Lecture 17: Recursive Methods and Recursive Structures as Collections
Date: Tuesday, March 29, 2016

Agenda

Announcements
- Lab 9: Bouncy GUI Ball due next Monday
- Lab 10: Final Project, just start thinking about project ideas and groups
Exam 2 Lab Practical recap
Lab 8: Furious Fowl recap
Lecture 16 assignment recap
Non-graphical recursive methods
Recursive structures as a collection

Due at the start of class, Thursday, March 31.

Please submit answers to these questions either as a hard copy (typeset or handwritten are OK) or by email to terescoj AT strose.edu by the start of class. Please use a clear subject line when submitting by email (e.g., CSC 252 Lecture 17 Assignment, Mary Smith). We will discuss these questions at the start of class, so no late submissions are accepted.

For this lecture assignment, you will be writing a Java application - a program that is not in a WindowController class but instead has a main method that does its work. It will be similar in structure to the Powers example. Write your program in Factorial.java. As in that example, you will need to create a keyboard Scanner to read in a number from the terminal and use System.out.println to issue a prompt and report your answer.

The problem we are going to solve is that of computing factorials. From math, you know that the factorial of a positive integer n, denoted n!, is the product of all the numbers from 1 up to n.

Write a main method of your Factorial class that prompts for and reads in a positive integer. You need not worry about error checking the input for this assignment. (2 points)
Write an iterative method loopFactorial that takes a single int as its parameter and returns the factorial of that value. Recall that an iterative method uses loop structures like for and while loops to do its work. Also update your main method to call the loopFactorial method on the number entered by the user, and print out the value returned. (4 points)
Write a recursive mathematical formulation, along the lines of the second power formula in the notes, for computing n!. (2 points)
Write a recursive method recFactorial that uses that formulation to compute factorials. Also update your main method to call the recFactorial method on the number entered by the user, and print out the value returned. (6 points)

Examples