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

©2000, John Wiley & Sons, Inc.Horstmann/Java Essentials, 2/e

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

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