CS
139 Lab: Practice with Looping -
Preconditional and Postconditional Loops
Objectives:
|
- Introduce students to
using loop structures in
programs.
- Provide students
practice in validation problems
|
Background:
|
Many computing problems
use the capability of the
computer to repeat calculations very quickly. This lab will
let you explore loop structures to solve various problems. |
New Terms:
|
- loop
- loop control variable
- off by one error
- infinite loop
- while
- do while
- for
|
Materials:
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Download Guess.java.
|
| Acknowledgment |
Lab by Nancy Harris |
Part 1 General Instructions:
Set up your programming
environment for this lab. You should
create a
folder into which you will store your programs.
Download the program from the
materials section.
Part 2 Using a post condition
loop in a guessing game.
For this part, you will create a loop that will prompt the user to
enter a character between 'a'
and 'j' and tell them if they have
guessed
the correct value that is generated by a random number generator.
That generator and producing the character to guess are
provided.
The program should count the number of guesses the user makes
before guessing the character. If the user guesses in 5 tries
or
less, announce that they win. If the user takes more than
five
tries, announce that the computer wins. In your final output
message, display the character the computer picked, the number of
guesses that the user made and who won. As a failsafe, if the
user makes more than10 guesses, end the loop and announce winner as
before, in other words, let the user keep guessing even if they can't
win.
- Create a set of test cases
(Examples). Since we are using a
random number generator, you will need to decide what circumstances you
want to test for. Include cases like guessing on the first
and
last tries. You should also build a test case where the user
makes too many guesses.
- Decide how you want to
structure your loop. You need to
make at least one pass, which would mean one prompt to ask the user for
a guess and a read of their value.
- Decide what your ending
condition will be. How will you know you have reached the end
of your looping?
- Code your loop.
- Test your code thoroughly.
- Save your work.
Part 3 Using a pre condition
loop in a guessing game.
For this part, you will ask the user if they want to play the guessing
game. If they say "yes", you execute
the code from Part 2.
If
they say "no", you end the game. At the
end of one round, you
ask
the user again if they want to play again. If so, you
continue to
play the game; if not, you end the game. If the user enters
'y', 'Y',
or "yes", consider it an affirmation that
they want to play. If
they enter anything else consider it as if it were a "no"
answer.
Each round should generate a new number, prompt the user for
the
correct guess and display the results.
- Create a set of test cases
(Examples) that you will test for correctness.
- Create a new copy of your
code as GuessV2.java.
- Look carefully at your code.
Where should the initialization occur for your new loop?
Where will the test be?
- Make sure that the code
needed for the game is contained within the body of the loop.
- Test your program thoroughly.
Part 4 Thought Questions
- Why did we suggest that you
use a post condition loop for the first part?
- Why did we suggest that you
use a pre condition loop for the second part?
- How would your code be
different if you used a pre condition loop for the first part?
- How would your code be
different if you used a post condition loop for the second part?
Part 5 - Optional - Higher or
lower
- Add code to your game to
tell the user whether their guess is higher or lower than the actual
value.
