Lab 10 - Chapter 7 Lab Arrays

Lab Objectives

Be able to declare and instantiate arrays

Be able to fill an array using a for loop

Be able to access and process data in an array

Be able to use an array of objects

Introduction

Everyone is familiar with a list. We make shopping lists, to-do lists, assignment lists, birthday lists, etc. Notice that though there may be many items on the list, we call the list by one name. That is the idea of the array, one name for a list of related items. In this lab, we will work with lists in the form of an array.

In Tasks #1 & 2, we will start out simple with a list of numbers. We will learn how to process the contents of an array by calculating the mean of all the numbers in the list, and then sorting all the numbers. We will use the selection sort algorithm, which is provided for you. Try to understand how the selection sort works.

In Task #3, we will move onto more complicated arrays, arrays that contain objects.

Task #1 Average Class

Look at the class provided in Blackboard called Average, which follows this UML diagram.

Average

-data [ ] :int -

mean: double

+Average( ):

+calculateMean( ): void

+toString( ): String

+selectionSort( ): void

This class will allow a user to enter 5 values into an array. It will then rearrange the data in descending order and calculate the mean for the data set.

Attributes:

data[] the array which will contain the integer values

mean the arithmetic average of the integer values

Methods:

Average the constructor. It will allocate memory for the array. Use a for loop to repeatedly display a prompt for the user which should indicate that user should enter integer 1, integer 2, etc. The constructor will then call the selectionSort and the calculateMean methods.

calculateMean this is a method that uses a for loop to access each integer in the array and add it to a running total. The total divided by the number of values (use the length of the array), and the result is stored into mean.

toString returns a String containing data in descending order and the mean.

selectionSortthis method uses the selection sort algorithm to rearrange the data set from highest to lowest.

Task #2 Average Driver

1. Run the AverageDriver class. This class only contains the main method. The main method will declare and instantiate an Average object. The Average object information will then be printed to the console.

2. Compile, debug, and run the program. It should output the data set from highest to lowest and the mean. Compare the computers output to your hand calculation using a calculator. If they are not the same, do not continue until you correct your code.

Task #3 Arrays of Objects

1. Copy the files Song.java (code listing 7.1), CompactDisc.java (code listing 7.2) and Classics.txt (code listing 7.3) from Blackboard. Song.java is complete and will not be edited. Classics.txt is the data file that will be used by CompactDisc.java, the file you will be editing.

2. In CompactDisc.java, there are comments indicating where the missing code is to be placed. Declare an array of Songs, called cd, to be of size 6.

3. Fill the array by creating a new song with the title and artist and storing it in the appropriate position in the array.

4. Print the contents of the array to the console.

5. Compile, debug, and run. Your output should be as follows:

Contents of Classics

Ode to Joy by Bach

The Sleeping Beauty by Tchaikovsky

Lullaby by Brahms

Canon by Bach

Symphony No. 5 by Beethoven

The Blue Danube Waltz by Strauss