2.12 Java1624: array objects, part 2

Revised: Fri Apr 01 16:30:58 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
    • Listings
• Preview
• Discussion and sample code
• Summary
• What's next?
• 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 listings while you are reading about them.

Listings

• Listing 1 . Reference variable declaration..
• Listing 2 . A three-dimensional array object of element type Button.
• Listing 3 . The generic class Object.
• Listing 4 . Primitive type conversions.
• Listing 5 . Initialization.
• Listing 6 . Placement of square brackets.
• Listing 7 . Creating the actual array object.
• Listing 8 . An array access expression.
• Listing 9 . Explicit initialization of array elements.
• Listing 10 . Create a two-dimensional rectangular array structure.
• Listing 11 . Using length to populate the leaves of the tree structure.
• Listing 12 . Display leaf object contents.
• Listing 13 . Beginning of a ragged array with two rows and three columns.
• Listing 14 . Create the leaf array objects.
• Listing 15 . Create the array object.
• Listing 16 . Populate the root object.
• Listing 17 . Populate the leaf array objects.
• Listing 18 . Display data in leaf array objects.
• Listing 19 . A triangular array.
• Listing 20 . Populate the leaf array objects.
• Listing 21 . A more general approach.
• Listing 22 . Populate the leaf objects.
• Listing 23 . Beginning of a more general case.
• Listing 24 . Populate the leaf array elements.
• Listing 25 . Display the output.
• Listing 26 . Complete program listing.

Preview

This module explains various details regarding the use of array objects in Java, and illustrates many of those details through the use of samplecode.

A sample program shows you three ways to emulate traditional two-dimensional rectangular arrays, and also shows you how to create and use ragged arrays.

Discussion and sample code

Array objects

A different syntax is required to create array objects than the syntax normally used to create ordinary objects.

Array objects are accessed via references.

Any of the methods of the Object class can be called on a reference to an array object.

The indices of a Java array object

Array objects encapsulate a group of variables, which don't have individual names. They are accessed using positive integer index values. The integerindices of a Java array object always extend from 0 to (n-1) where n is the length of the array encapsulated in the object.

Multidimensional arrays

Array objects in Java encapsulate one-dimensional arrays. However, the component type of an array may itself be an array type. This makes it possibleto create array objects whose individual components refer to other array objects. This is the mechanism for creating multi-dimensional or ragged arrays in Java.