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CSC $205$ Lab $2$ Part II: Array Stats Program & OOP Review

Due by Monday, January $29$th$,2$:$30$ PM along with your Clock files from Part I to your scratch area on

our Linux server $($cobra$).$ See end of lab for details on submitting. This lab is worth $10$ points.

Goals

After completing this lab, you should be able to:

$$ Work with loops and arrays in Java.

$$ Use and call multiple class methods and understand the value of structured

programming.

$$ Make use of instance methods and understand how both instance methods and

class methods can be used within the same class.

$$ Be able to differentiate between instance variables and class variables.

$$ Write constructors, getters, and setters.

Lab Setup

Change into your Lab$2$ directory $($cd Lab$2).$ Now, let us copy over a source file I have

already started for you $($Stats$.$java$)$ to use for your program along with a sample

executable file.

cp $/$pub$/$digh$/$CSC$205/$Lab$2/*.$

The Array Stats Program

Two of the measures taken on a group of data are the range of data and the mean of data.

The range of a group of data is defined to be the difference of the largest element and the

smallest element. The mean is defined to be the average of the group of data. Complete

the program Stats so that it will successfully compute the range and mean of a data set

that is input by a user.

Input and Output

The input to your program will be n positive integers one per line from the keyboard,

where $1<$ n $<100.$ The end of all input is indicated by a line with the integer $0.$

Following the input set, your program should print out the range of the input as well as

the mean with appropriate output prompts.

Sample Run

Please Input Your Values $($Enter a $0$ to Stop$)$:

$4$

$6$

$2$

$20$

$10$

$0$

The range of your $5$ items is: $18$

The mean of your $5$ items is: $8\mathrm{.}4$

$2$

Program Design

Your main method has already been set up for you. You simply need to code the bodies

of three methods: fillUp, range, and mean.

Method fillUp is used to read all the input values into the array List and return the

number of items read in back to the main method.

Method range returns the difference between the maximum value and minimum value

in List. The calculation of the maximum and minimum can be done using a single for

loop.

Method mean returns the average of the input values. Notice that it returns a double

value so you will need to use some typecasting. There is no need to worry about a

specific double precision for this lab.

In finishing your range & mean methods, make sure your loop does NOT go all the

way to List.length. That is why we sent in numItems as a parameter. We want it

to only find the range and mean of numItems in the array List.

OOP Review

Look at class Person on the attached handout. Each person has instance variables for

an id and name associated with them. Notice also the private class variable

personCount. We will use this class variable to assign a unique id to each person in

the order they are $$created$.$

Unlike instance variables, which as the name implies come with every instance of a class

$($i$.$e$.,$ object$),$ class variables are associated with the class instead. This means, only one

copy of this variable is shared among all objects of this class and therefore the value of

this variable is the same for all of the objects.

To declare a class variable we use the keyword static. Class methods are of course

similarly declared. Notice the static method getCount$().$ Do you see how its value is

shared among all possible variables $($instances$)$ of type person? This is in contrast to the

id$,$ which is different for each person.

Finally, notice how we can invoke the static method. We can call it with in instance of

the class, i$.$e$.,$ an object $($e$.$g$.,$ sue.getCount$())$ or$,$ and this is different, by just

referring to the name of the class, i$.$e$.,$ Person.getCount$()).$

Now, in the space below, trace through and give the output of the StaticTest

program shown.

$3$

Embellishing the Person Class

$$ Let us overload our constructor by adding a default $($no$-$args$)$ constructor to

Person that defines an object to have the name $$N$/$A$$ and an id of $1.$ Use the

this operator appropriately, and be sure to increment personCount.

$$ Add a setter method named reset that can be used to reset the two private

instance variables of this class to two values passed in as parameters. This will

allow your Person class to now be mutable.

$$ Add getter methods getName and getId that can be used to retrieve these two

private variables.

Finally, let us test our new methods at the end of the StaticTest program. Declare a

Person object samplePerson that uses the default constructor. Next, reset it to your

own name and the last four digits of your social security number using the reset

method. Finally, print out your name and id using your getter methods.

Lab Submission

Now, let us copy over your work for grading on $/$scratch$.$ Remember to replace

last$\_$fm with your cobra login name below.

cp Stats.java $/$scratch$/$csc$205/$last$\_$fm$/$Labs

cp Person.java $/$scratch$/$csc$205/$last$\_$fm$/$Labs

Next, chang