2.11 Jb0150: java oop: a gentle introduction to java data types

Revised: Sun Mar 27 21:20:50 CDT 2016

This page is included in the following Books:

• Programming Fundamentals with Java
• Object-Oriented Programming (OOP) with Java

Table of contents

• Preface
  • General
  • Prerequisites
  • Viewing tip
    • Figures
• Discussion
  • Introduction
  • Primitive types
    • Whole-number types
    • Floating-point types
    • The character type
    • The boolean type
  • User-defined or reference types
  • Sample program
• Miscellaneous

Preface

General

This module is part of a collection of modules designed to help you learn to program computers.

It introduces Java data types.

Prerequisites

In addition to an Internet connection and a browser, you will need the following tools (as a minimum) to work through the exercises in these modules:

• The Sun/Oracle Java Development Kit (JDK) (See (External Link) )
• Documentation for the Sun/Oracle Java Development Kit (JDK) (See (External Link) )
• A simple IDE or text editor for use in writing Java code.

The minimum prerequisites for understanding the material in these modules include:

• An understanding of algebra.
• An understanding of all of the material covered in the earlier modules in this collection.

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 Figureswhile you are reading about them.

Figures

• Figure 1 . Range of values for whole-number types.
• Figure 2 . Definition of floating point.
• Figure 3 . Different ways to represent 623.57185.
• Figure 4 . Relationships between multiplicative factors and exponentiation.
• Figure 5 . Other ways to represent the same information.
• Figure 6 . Still other ways to represent 623.57185.
• Figure 7 . Range of values for floating-point types.
• Figure 8 . Example of the use of the boolean type.

Discussion

Introduction

Type-sensitive languages

Java and some other modern programming languages make heavy use of a concept that we refer to as type , or data type .

We refer to those languages as type-sensitive languages . Not all languages are type-sensitive languages. In particular, somelanguages hide the concept of type from the programmer and automatically deal with type issues behind the scenes.

So, what do we mean by type?

One analogy that comes to my mind is international currency. For example, many years ago, I spent a little time in Japan and quite along time on an island named Okinawa (Okinawa is now part of Japan) .

Types of currency

At that time, as now, the type of currency used in the United States was the dollar. The type of currency used in Japan was the yen, and thetype of currency used on the island of Okinawa was also the yen. However, even though two of the currencies had the same name, theywere different types of currency, as determined by the value relationships among them.

The exchange rate

As I recall, at that time, the exchange rate between the Japanese yen and the U.S. dollar was 360 yen for each dollar. The exchange ratebetween the Okinawan yen and the U.S. dollar was 120 yen for each dollar. This suggests that the exchange rate between the Japanese yen and theOkinawan yen would have been 3 Japanese yen for each Okinawan yen.