Conditionals - Assignment 4

CSCI 135
Fundamentals of Computer Science I
Fall 2017

ASSIGNMENT 4

The goal of this assignment is to use iteration in Java. You will be using looping constructs (while, do...while, and for loops) in your code. Just because this lab is about iteration, doesn't mean you won't have to use conditionals (if statements) also. Like our last assignment, be sure you pay attention to your header comment and other comments, your indentation and variable names, and careful use of whitespace and curly braces.

Part 1: while Loops
Write a program named GuessUntil.java that generates a random number between 1 and 10. To do this, recall that the command:

int number = (int) ((Math.random( )* 10) + 1);

will generate a random integer within that range.

The user can enter guesses at the number until they get it right. To do this, we need a way to get user input, not just command line input, into your program. We'll talk about this more later on, but for now, here is "magic" code that does that.

At the top of your program, before the public class <whatever> statement, either above or just below your header comment, put in this line:

import java.util.Scanner;

At the top of your main method, put in this line:

Scanner keyboard = new Scanner(System.in);

What this does is allow you to define a variable named keyboard that is of type Scanner. This is the Java class for getting user input. Now, whenever you need interactive input from the user, use the line:

guess = keyboard.nextInt();

This line says to use the variable "keyboard" to get the next integer that the user types in at the keyboard. When you run your program, make sure that you click inside the console window before entering input. Also, the user should know what they are expected to type at the keyboard, so you should always print out a line (a prompt) that tell the user what is expected. For example:

System.out.print("Enter a number between 1 and 10: ");
guess = keyboard.nextInt();

Would look to the user like:

Enter a number between 1 and 10:

Your program should use some form of a while loop to continue getting user guesses until they finally guess the number that was randomly generated. You can decide whether a while loop or a do...while loop is more appropriate. When the user finally guesses the correct number, print out:

You got it!

Part 2: for Loops
Rewrite your previous program so that the user only gets three guesses. Name this program GuessThree.java. Use a for loop in this program. Each time the user guesses wrong, you should print out whether the guess was too high or too low. If they get it right you should print out "You got it!"

If the user guesses correctly before their three guesses are used up, you should exit the loop. IMPORTANT! Try to figure out a way NOT to use a break statement to terminate your loop early. You will lose a point if you use a break statement.

Here is an example output when the user guessed on the second try:

Enter a number between 1 and 10: 5
Your guess was too low.
Enter a number between 1 and 10: 7
You got it!

Part 3: Nested Loops
Write a program that asks the user to enter the size of a traingle (an integer from 1 to 50). Name this program Triangle.java. Display the triangle by writing lines of asterisks. The first line will have one asterisk, the next two, and so on, with each line having one more asterisk than the previous line, up to the number entered by the user. On the next line,write one fewer asterisk and continue by decreasing the number of asterisks by 1 for each successive line until only one asterisk is displayed. (Hint: Use nested for loops; the outside loop controls the number of lines to write, and the inside loop(s) control(s) the number of asterisks to display on a line.)

For example, if the user enters 3, the output would be:

*
**
***
**
*

This is similar to the StarTriangle example that we saw in class, but has the added twist of printing asterisks up to and then down from the number the user has entered.

Grading Each of the three programs is worth 10 points each, for a total of 30 points. For each program, you will be graded according to the following criteria:

Grade Item GuessUntil GuessThree Triangle Points Earned

Program Compiles
2
2
2

Program Runs
2
2
2

Header Comment
2
2
2

Program Runs Correctly
4
4
4

Grade Item	GuessUntil	GuessThree	Triangle
Program Compiles	2	2	2
Program Runs	2	2	2
Header Comment	2	2	2
Program Runs Correctly	4	4	4

Submission. Submit all three programs GuessUntil.java, GuessThree.java, and Triangle.java via Moodle. Be sure each submitted source file has the required header with your name, and a description of the program. Also be sure to submit the .java source files and not the .class files!

Page last updated: August 15, 2018