Using MsgBox3.java or Average.java as examples, create a Java non-GUI stand-alone application that displays a histogram. A histogram is a kind of non-GUI bar chart that shows how many times a given value occurs in an input sample. The more times a given value appears, the longer the bar becomes for that value.
This program can be used to examine all sorts of
frequency data.
In the example below I used this histogram
program to analyize the scores of a previous COP 2800 Exam #1.
I entered in all the question numbers that
were answered incorrectly, for each and every student exam.
(For instance, on the first student answered questions
1, 3, 4, and 19 incorrectly, so I input: 1 3 4 19.
The next student had questions 4, 17, 19, and 22 incorrect, so I continued
by entering 4 17 19 22 this time.
I kept this up for each student's exam.)
The output
shows 8 questions were much harder than the rest,
and that two questions were so trivial nobody answered them
incorrectly.
(I have used this information to update my test bank.)
To actually draw the horizontal lines of the histogram, you
must use the
utils.TextKit.lineOfStars method
you created in TextKit Project.
This project will require the use of arrays and input.
Write a Java non-GUI program that will accept as
input integer values, each value is a number between 1 and 25,
with one value per line.
The user will indicate the end of the list by signaling
EOF, which on DOS/Windows systems is done by hitting a
control-Z.
(On Unix and Macintosh systems EOF can be signaled by hitting
a control-D instead.)
The output shall consist of 25 lines of stars (asterisks),
one line for each of the possible input values (the numbers
1 to 25.
The number of stars drawn shows how many times each value
was entered as input.
Each line should be labeled with the value it is showing the bar
for.
So, if the input was:
C:\TEMP> java Histogram
Enter integers <= 25, one per line, hit control-Z when done:
1
2
4
2
1
2
control-Z
Then the output would be:
1: **
2: ***
3:
4: *
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
Your Java program must use the method
called lineOfStars to create the stars for each line
of output.
This method must take a single
int parameter which says how many stars to draw.
This method must
be a static
method of a class called TextKit,
which must be in a
package called utils.
This should be the method you created for the previous project.
You are not allowed to modify your
utils.TextKit class in any way from what you completed
in the previous project without the approval of your instructor.
Your program will have its class in the default, nameless package
and not in the utils package (where TextKit
is).
(Note only a few of the more than 100 values actually typed by me are shown here.) You can read the input data from a file too, using a command line such as:
C:\TEMP> java Histogram < data.txt
(To practice using the data I used, download HistogramData.txt and use that as the input file, as shown above.)
C:\TEMP> java Histogram Enter integers <= 25, one per line, hit control-Z when done: 1 5 16 11 2 23 3 2 ... 16 control-Z Histogram showing how many students answered each question wrong: 1: ** 2: ***** 3: ***** 4: 5: *** 6: ** 7: ***** 8: 9: ** 10: *************** 11: ***** 12: ******** 13: ************* 14: ******** 15: ******* 16: *************** 17: *** 18: ************** 19: ******************* 20: ********** 21: ******* 22: ******** 23: ************* 24: ************** 25: **************** C:\TEMP>
Many student make the mistake of thinking the input data is the length of each bar. Take another look at the sample data and the resulting output. The input is not the lengths of the 25 bars!
It may help to think of the input as a series of
bar numbers
instead.
For the first part of your program you must read these
numbers one at a time, and increment a counter,
(that stores that bar's length), for each one.
You repeat this until you run out of input data.
The second part of your program needs to print each of
the 25 bars.
See the Integer class's static
methods for a way
to convert a String (that you read in)
to an int.
Java 5 provides input methods (the Scanner class)
that make input very easy.
You are encouraged to use them.
You program should be easily read and well commented, including your
name.
Remember the best programs result when you start with the design,
then make a skeleton class containing your design as comments, and
finally fill in the code below each comment, one piece at a
time.
If you wish you can send me your design skeleton
program
before starting to write any code, to make sure you're on the
right track.
Ask me for help if you get stuck!
Email to me a copy of the souce code for your Histogram class.
You do not need to send your .class files nor your
utils package.
Send projects to
.
Please use a subject such as "Java Histogram Project"
so I can tell which emails are submitted projects.
Send project questions to . Please use a subject such as "Java Histogram Project Questions" so I can tell which emails are questions about the project.
Please review Submitting Assignments and Project Grading Criteria from your class syllabus for further details.