2.5 Jb0120: java oop: a gentle introduction to java programming

Revised: Sun Mar 27 19:13:53 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
    • Listings
• Discussion and sample code
  • Introduction
  • Compartments
  • Checkout counter example
  • Sample program
• Run the program
• Miscellaneous

Preface

General

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

It provides a gentle introduction to Java programming.

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 Figuresand Listings while you are reading about them.

Figures

• Figure 1 . A checkout counter algorithm.

Listings

• Listing 1 . Program named Memory01.
• Listing 2 . Batch file for Memory01.

Discussion and sample code

Introduction

All data is stored in a computer in numeric form. Computer programs do what they do by executing a series of calculations on numeric data. It is the order and the pattern of those calculations that distinguishes one computer program from another.

Avoiding the detailed work

Fortunately, when we program using a high-level programming language such as Java, much of the detailed work is done for us behind the scenes.

Musicians or conductors

As programmers, we are more like conductors than musicians. The various parts of the computer represent the musicians. We tell them what to play, and when to play it, and if we do our job well, we produce a solution to a problem.

Compartments

As the computer program performs its calculations in the correct order, it is often necessary for it to store intermediate results someplace, and then come back and get them to use them in subsequent calculations later. The intermediate results are stored in memory, often referred to as RAM or Random Access Memory .

A mechanical analogy

We can think of random access memory as being analogous to a metal rack containing a large number of compartments. The compartments are all the same size and are arranged in a column.Each compartment has a numeric address printed above it. No two compartments have the same numeric address. Each compartment also has a little slot into which you can insert a name or a label for the compartment. No two compartments can have the same name.

Joe, the computer program

Think of yourself as a computer program. You have the ability to write values on little slips of paper and to put them into the compartments. You also have the ability to read the values written on the little slips of paper and to use those values for some purpose. However, there are two rules that you must observe: