Lecture Java methods: Object-oriented programming and data structures (2nd AP edition): Chapter 2 - Maria Litvin, Gary Litvin

Chapter 2 - An introduction to software engineering. This chapter gives a glimpse of how software development evolved from artisanship into a professional engineering discipline. At the same time, students will get familiar with Java development tools and run their first programs.

An Introduction to Software

Engineering

Copyright © 2011 by Maria Litvin, Gary Litvin, and Skylight Publishing All

rights reserved Chapter 2

Java Methods

Object-Oriented Programming

and Data Structures

Maria Litvin ● Gary Litvin

2nd AP edition with GridWorld

Objectives:

• Understand the software development

process, tools, and priorities

• Understand compilers and interpreters

• Learn about Java Virtual Machine, bytecode

• Learn to set up and run simple console

applications, GUI applications, and applets in Java

• Learn basic facts about OOP

Software Today:

1,580,000,000

• Graphics / arts / digital photography

• Often cryptic code

y languag

Smalltalk-C#

Log o

Python Cobol

D

Fortres s Groovy

 translates the source

into object code

• Debugger

 steps through the program “in slow motion” and helps find logical mistakes (“bugs”)

Compil er

Object code

le program

Edito

r

Source code

Compil er

Object code

Edito

r

Source code

Compil er

Object code



Interpreted Languages:

Edit-Run

Edito r

Source code

Interpret

while the program is interpreted

 the interpreted program is slower

Java’s Hybrid Approach:

Compiler + Interpreter

• A Java compiler converts Java source

code into instructions for the Java

Virtual Machine.

• These instructions, called bytecode, are

the same for any computer / operating system

• A CPU-specific Java interpreter

interprets bytecode on a particular

computer

 

Interpreter

• Interpreter is faster and smaller than it would

be for Java source

• Source code is not revealed to end users

• Interpreter performs additional security

checks, screens out malicious code

JDK (cont’d)

• Developed by Sun Microsystems (now Oracle); free download

• All documentation is online

• Many additional Java resources on the Internet

http://www.oracle.com/technetwork/java/javase/downloads/

Java IDE

• GUI front end for JDK

• Integrates editor, javac, java, appletviewer, debugger, other tools:

 specialized Java editor with syntax highlighting, autoindent, tab setting, etc.

the offending source code line

• Usually JDK is installed separately and an

IDE is installed on top of it

Types of Programs

• Console applications • GUI applications

• Applets

Console Applications

C:\javamethods\Ch02> path=%PATH%;C:\Program

Files\Java\jdk 1.5.0_07\bin

C:\javamethods\Ch02> javac Greetings2.java

C:\javamethods\Ch02> java Greetings2

Enter your first name: Josephine

Enter your last name: Jaworski

Hello, Josephine Jaworski

Press any key to continue

• Simple text dialog:

prompt input, prompt input result

Command-Line Arguments

C:\javamethods\Ch02> javac Greetings.java

C:\javamethods\Ch02> java Greetings Josephine

Jaworski

Hello, Josephine Jaworski

public class Greetings

{

public static void main(String[ ] args)

{

String firstName = args[ 0 ];

String lastName = args[ 1 ];

System.out.println("Hello, " + firstName + " " + lastName);

}

}

line

Command-arguments are passed

to main

as an array

of Strings.

Command-Line Args (cont’d)

• Can be used in GUI applications, too

• IDEs provide ways to set them (or

prompt for them)

Josephine Jaworski

Scanner kboard = new Scanner(System.in);

System.out.print("Enter your first name:

");

String firstName = kboard.nextLine( );

System.out.print("Enter your last name:

");

String lastName = kboard.nextLine( );

System.out.println("Hello, " + firstName + " " + lastName);

System.out.println("Welcome to Java!");

}

}

Promp ts

Slider

HelloGui window = new HelloGui( );

// Set this window's location and size:

// upper-left corner at 300, 300; width 200, height

100

window.setBounds(300, 300, 200, 100);

window.setDefaultCloseOperation(JFrame.EXIT_ON_CL OSE);

window.setVisible(true);

}

}

GUI libraries

No main in applets: the

init method is called by

JDK’s appletviewer or the

browser

• An object may have its own “memory,”

which may contain other objects

• An object has a set of methods that can

process messages of certain types

OOP (cont’d)

• A method can change the object’s state, send messages to other objects, and create new objects

• An object belongs to a particular class, and the functionality of each object is determined

by its class

• A programmer creates an OOP application by defining classes

The Main OOP Concepts:

• Inheritance: a subclass extends a superclass;

the objects of a subclass inherit features of

the superclass and can redefine them or add new features

• Event-driven programs: the program

simulates asynchronous handling of events; methods are called automatically in response

to events

OOP Benefits

• Facilitates team development

• Easier to reuse software components and write reusable software

• Easier GUI (Graphical User Interface) and multimedia programming

Review (cont’d):

• What is a console application?

• What are command-line arguments?

• What is a GUI application?

• What is the difference between a GUI application and an applet?

• What is OOP?

• Define inheritance