©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Chapter 1: Introduction 1 Chapter 1...

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Chapter 1: Introduction1

Chapter 1

Introduction

Welcome to CS46A

• www.horstmann.com/sjsu• Green Sheet• Register for Companion Lab• Send email to add• First homework due September 7

Course Goals

• Introduction to computer science• Programming concepts• Problem solving• Object-oriented programming• Introduction to Java (but not a Java course)• Foundation for CS majors

Prerequisites

• Computer savvy (file management, text editing)

• Problem solving skills• Time management• High school math (algebra, trigonometry)• No prior programming background required

What is a computer?

• Central processing unit• Memory• Peripherals• Executes very simple instructions• Executes instructions very rapidly• General purpose device• Programs describe specific actions

Figure 1Central Processing Unit

Figure 2CPU Chip Detail

Figure 3RAM Chips

Figure 4A Hard Disk

Figure 5A High-CapacityFloppy Disk and ItsDrive

Figure 6A CD-ROM Drive

Figure 7Tape Backup Drives and Data Tape

Figure 8A Personal Computer

Figure 9A Motherboard

Figure 10Schematic Diagram of aPersonal Computer

Programming Languages

• Machine/Virtual Machine21 40 16 100 163 240

• Assembleriload intRatebipush 100if_icmpgt intError

• High-level languageif (intRate > 100) . . .

The Java Programming Language

• Simple• Safe• Platform-independent ("write once, run

anywhere")• Rich library• Designed for the internet

Figure 12An Applet on a Web Page

Becoming Familiar with your Computer

• Login• Locate the Java compiler• Understand files and folders• Write a simple program (later)• Save your work

Figure 13A Startup Screen with Icons

Figure 14A Directory Hierarchy

Figure 15Screen Layout of an Integrated JavaEnvironment

A simple program

• public class ClassName• public static void main(String[] args)

• object.methodName(parameters)• System class• System.out object• println method

Program Hello.java

public class Hello{ public static void main(String[] args) { System.out.println("Hello, World!"); }}

Compiling and Running

• Type program into text editor• Save• Open command shell• Compile into byte codesjavac Hello.java

• Execute byte codesjava Hello

Figure 16From Source Code toRunning Program

Edit–Compile–Debug Loop

Figure 17

Errors

• Syntax errorsSystem.ouch.print("...");System.out.print("Hello);

• Detected by the compiler• Logic errorsSystem.out.print("Hell");

• Detected (hopefully) through testing

Objects and Classes

• Object: entity that you can manipulate in your programs (by invoking methods)

• Each object belongs to a class• Class: Set of objects with the same behavior• Class determines legal methods"Hello".println() // Error"Hello".length() // OK

A Class has 4 Purposes:

• A class specifies which methods you can apply to its objects

• A class is a factory for objects (new)• A class is a holding place for static methods

and objects (main, System.out)• A class defines implementation details:

object fields and code for methods

Rectangle class

• Construct a rectangle:new Rectangle(5, 10, 20, 30)new Rectangle()

• Object variables:Rectangle cerealBox = new Rectangle(5, 10, 20, 30);Rectangle crispyCrunchy;

• Sharing objects: crispyCrunchy = cerealBox;

Figure 18Rectangular Shapes

Figure 19

Rectangle Objects

Object

Refers to an

An Object Variable That

Figure 20

An Uninitialized ObjectVariable

Figure 21

Figure 22Two Object Variables That Refer tothe Same Object

Rectangle class 2

• Print a rectangleSystem.out.println(cerealBox);

• Translate a rectanglecerealBox.translate(15, 25)

• Import statement:import java.awt.Rectangle;

Program MoveRectangle.java

import java.awt.Rectangle;

public class MoveRectangle{ public static void main(String[] args) { Rectangle cerealBox = new Rectangle(5, 10, 20, 30); cerealBox.translate(15, 25); System.out.println(cerealBox); }}

Algorithms 1

• Example: You put $10,000 into a bank account that earns 5% interest per year. Interest is compounded annually. How many years does it take for the account balance to be double the original?

Year Balance0 $10,000.001 $10,500.002 $11,025.003 $11,576.25

Algorithms 2

• Unambiguous• Executable• Terminating• If you can't find an algorithm, the computer

can't solve your problem

©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Chapter 1: Introduction 1 Chapter 1...

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