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COSC 1331 Lab 2: Counting Coins and Making Change The Coins Class Objectives • Use methods. • Use local variables. • Use arithmetic expressions. • Use Scanner to input values. • Use a class constant.
COSC 1331
Lab 2:
Counting Coins and Making Change
The
Coins
Class
Objectives
•
Use methods.
•
Use local variables.
•
Use arithmetic expressions.
•
Use Scanner to input values.
•
Use a class constant.
Hand-in Requirements
All projects and laboratories will be submitted electronically through Canvas.
Zip up
your entire lab directory to submit as the source.
(Right click on the lab folder and
follow
Send To > Compressed (zipped) Folder
or
7-Zip > Add to "lab2.zip"
).
The lab
folder should include the following:
•
Coins.java
•
CoinsOutput.txt
Tasks
Write a program that prints
Lab 2 written by YOURNAME
and calls two methods:
1.
Input the number of quarters, dimes, nickels, and pennies from the user.
out the number of coins and total value in dollars.
2.
Input the number of cents from the user.
Determine and print out the number of
quarters, dimes, nickels, and pennies to add up to that number of cents.
No, you
can't use all pennies.
Details
Getting Input from the User
You can get input from the user using a Scanner object.
Here is an example program
with key lines in bold.
import java.util.*;
public class HalfDollar {
public static final Scanner CONSOLE = new Scanner(System.in);
public static void main(String[] args) {
halfDollarAmount( );
}
public static void halfDollarAmount( ) {
System.out.print("Enter the number of half dollars: ");
int halfDollar = CONSOLE.nextInt( );
double amount = halfDollar * 0.50;
System.out.println(halfDollar + " half dollars is $" + amount);
}
}
The import statement tells Java that we want to use Java's
java.util
package (Scanner is
part of this package).
The statement:
public static final Scanner CONSOLE = new Scanner(System.in);
declares a special kind of variable (a
class constant
) named
CONSOLE
of
type
Scanner
and stores an "object" for input from the keyboard
in
CONSOLE
.
CONSOLE
can be used anywhere in the class.
The first two statements of the
halfDollarAmount
method:
1.
prompt the user for information, and
2.
input a number from the keyboard and stores the number in a variable
named
halfDollar
.
You only need the declaration/assignment for
CONSOLE
once in the class.
On the other
hand, you need prompt and input statements for each value you want the user to enter.
Local Variables
You should have local variables for each value that is entered and each value that you
calculate.
For example, for the first method there should be a local variable that stores
the total dollar amount of the change, as well as a local variable for the total number of
coins.
Making Change
For the second method, we can use integer division and the mod operator to make
change.
Suppose the user enters 99 as the number of cents.
The sequence of
calculations should be as follows.
1.
The integer division
99
/
25
can be used to determine the number of quarters (3).
2.
Using the mod operator
99
%
25
determines the remaining number of cents to be
converted into change (24).
3.
Integer division
24
/
10
can be used again to determine the number of dimes (2).
4.
The mod operator
24
%
10
can be used again to determine the remaining amount
(4).
5.
Next, for nickels, integer division
4
/
5
for the number of nickels (0) and a mod
operation
4
%
5
for the remaining amount (4).
6.
Whatever is left is the number of pennies (4).
Of course the values that were calculated (3, 24, 2, 4, 0, 4) would be different if the user
enters something different from 99.
This means we should have variables to store all of
these values.
For example, we might have a variable named
cents
to hold the value that
the user entered, a variable named
remainingAfterQuarters
for the remaining amount
after the quarters are determined, which could be assigned by:
int remainingAfterQuarters = cents % 25;
Output File
Include the output of your program in a file named
CoinsOutput.txt
.
Rubric
Your program should compile without any errors.
A program with more than one or two
compile errors will likely get a zero for the whole assignment.
The following criteria will also be used to determine the grade for this assignment:
•
[Points] If the main method of your program prints "Lab 2 written by [...]".
•
[Points] If your submission was a Zip file named
lab2.zip
containing a folder
named
lab2
, which contains the other files.
•
[Points] If your Java program was in a file named
Coins.java
.
•
[Points] If the output of your Java program was in a file named
CoinsOutput.txt
.
•
[Points] If your program contains a comment that describes what the program
