3.21 Java3020: interfaces, object arrays, etc.

Revised: Sun Apr 03 17:27:47 CDT 2016

This page is included in the following Books:

• ITSE 2321 - Object-Oriented Programming (Java)
• Object-Oriented Programming (OOP) with Java

Table of contents

• Preface
  • Viewing tip
    • Figures
    • Listings
• Preview
• General background information
• Discussion and sample code
• Run the program
• Summary
• What's next?
• Online video links
• Miscellaneous
• Complete program listing

Preface

This module is one of a series of modules designed to teach you about Object-Oriented Programming (OOP) using Java.

Viewing tip

I recommend that you open another copy of this document in a separate browser window and use the following links to easily find and view the Figures and Listings while you are reading about them.

Figures

• Figure 1 . Command line output for Prob05.

Listings

• Listing 1 . Beginning of driver class for Prob05.
• Listing 2 . The interface named Prob05X.
• Listing 3 . Beginning of the class named Prob05MyClassA.
• Listing 4 . The method named getModifiedData.
• Listing 5 . The method named getData.
• Listing 6 . Overridden toString method.
• Listing 7 . Beginning of the class named Prob05MyClassB.
• Listing 8 . The method named getModifiedData.
• Listing 9 . The getData and toString methods.
• Listing 10 . Print three items of information.
• Listing 11 . Three more print statements.
• Listing 12 . Print the references to the two objects.
• Listing 13 . Complete program listing

Preview

In this module, you will learn about :

• Interface definitions
• Implementing an interface in a class definition
• Defining interface methods in a class definition
• Storing references to new objects in elements of an array of type Object
• Casting elements to an interface type in order to call interface methods
• Parameterized constructors
• Overridden toString method

Program specifications

Write a program named Prob05 that uses the class definition shown in Listing 1 to produce the output shown in Figure 1 on the command line screen.

No graphic output images required

There are no graphic output images required by this program. Therefore, it can be compiled and executed without a requirement to have Ericson's medialibrary on the classpath.

Required text output

The output, which appears on the command line screen, consists of the six lines of text shown in Figure 1 .

Because the program generates random data for testing, the actual values will differ from one run to the next. However, in all cases:

• The values in the first row of numbers will be a sequence of consecutive integers in increasing algebraic order from left to right.
• All three values in the second row of numbers will match the value of the center number in the first row of numbers.
• All three values in the third row of numbers will be algebraically five greater than the values in the second row of numbers.

New classes

You may define new classes as necessary to cause your program to behave as required, but you may not modify the class definition for the class named Prob05 shown in Listing 1 .