CS 209 Programming in Java #1

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CS 209 Programming in Java

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Introduction

Spring, 2006

Instructor: J.G. Neal

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Topics

• CS 209 Target Audience

• CS 209 Course Goals

• CS 209 Syllabus - See handout

• Java Features, History, Environment

• Java Development Software

• Information Sources

• Applications and Applets

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CS 209 Programming in Java

• Target audience:

– Designed for students with previous programming experience

– Ideally the student should have some experience with: • Arrays,

• Functions/procedures,

• Passing parameters to functions/procedures

CS 209 - Course Goals

• Goals:

– Learn the Java programming language

– Learn about the Java Virtual Machine and Java API – Learn to design, develop, debug, and run Java programs

• Web-based Java applets • Stand-alone Java applications – Learn to use Java development tools – Learn to use good principles and practices

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Features of Java

• Provides for both web-based and stand-alone applications • Is totally object-oriented

• Provides networking capabilities for distributed systems • Provides for dynamic interactive programs

• Simplifies memory management - automatic garbage collection • Supports multithreading - concurrent processing

• Is portable and platform independent; interpreted

– Programs run on the Java Virtual Machine at runtime • Provides for security

• Very large set of library packages in the Java API

– Graphics, user interface capabilities, networking, database operations, file manipulations, etc.

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Some Java History

• Developed in the early 1990’s at Sun Microsystems

– Originally called “Oak”

– Designed for use in embedded consumer electronic applications

• Redesigned for developing Internet applications and renamed “Java”

• Releases:

– JDK 1.0, the first Java programming language release, was officially announced in May 1995

– JDK 1.1 released in 1997

– Java 2 SDK v 1.2 (a.k.a. JDK 1.2), 1998 – Java 2 SDK v 1.3 (a.k.a. JDK 1.3), 2000 – Java 2 SDK v 1.4 (a.k.a. JDK 1.4), 2002 – Java 2 SDK v 1.5 (a.k.a. JDK 1.5), 2004

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JDK Editions

• Java Standard Edition (J2SE) **

– J2SE can be used to develop client-side standalone applications or applets.

• Java Enterprise Edition (J2EE)

– J2EE can be used to develop server-side applications such as Java servlets and Java ServerPages.

• Java Micro Edition (J2ME).

– J2ME can be used to develop applications for mobile devices such as cell phones.

** This course uses the J2SE

Java Program (MyProgram.java) Java Compiler (javac) Java Bytecode (MyProgram.class) HW-based Platform (Sun + Solaris OS) Java API

Interpreter or Java Platform:

Java Virtual Machine

HW-based Platform (PC + WIN OS) Java API

HW-based Platform (Mac + Mac OS) Java API

The Java

Environment

Editor

(Source Code File)

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Java Development Software

Sun Microsystems, Inc.

• Java 2 Standard Edition (J2SE) SDK from Sun Microsystems

– No cost download from the Sun Microsystems website

• J2SE includes:

• javac - Compiler for the Java language

• java - Launcher for execution of Java applications

• javadoc - API documentation generator

• appletviewer - Run applets without a web browser

• jar - Manage Java Archive (JAR) files

• jdb - Java Debugger

• javah - C header and stub generator

• javap - Class file disassembler

• extcheck - Utility to detect Jar conflicts

• HtmlConverter - Converts to a new HTML file with tags for invoking the Java plugin

• among others . . .

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Java Development Software

Integrated Development Environments (IDEs):

• NetBeans IDE (http://www.netbeans.org; http://www.sun.com)

• Eclipse IDE (http://www.eclipse.org)

• Borland JBuilder (http://www.borland.com)

• Sun Java Studio (http://www.sun.com)

• IBM WebSphere (http://www.ibm.com)

• JCreator (http://www.jcreator.com)

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Object-Oriented Programming

Benefits:

– Software modularity – Information hiding

– A wealth of well-tested predefined classes, especially the Java API (part of the J2SE)

– Software reuse

– Enhanced programmer productivity

Object-Oriented Programming

• Fundamental principle:

– Encapsulation of data and methods in an object

• Objects:

– Real world objects have state (attributes or data) and behavior (actions or operations)

– A software object

• maintains its state (attributes or data) in variables and • implements its behavior as methods

• A class:

– Is a “blueprint” or “template”

– Defines the variables and methods common to all objects of a certain kind

• An object is an instance of a class

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Object-Oriented Fundamentals

• Programs are developed in the form of classes:

– The conceptual entities/objects that comprise the program

• Classes are organized into a hierarchy

– Levels:

• The higher the level, the more generic • The lower the level, the more specific

– Inheritance: subclasses automatically have the variables and methods of their superclasses

– Inherited methods can be overridden in a subclass

• Programmers write their new programs building on the existing Java Class Hierarchy (Java 2 API)

Bicycles

Racing Bikes

Mountain Bikes Tandem Bikes

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Example Application-Specific Hierarchy

Employee

SalariedEmployee HourlyEmployee TemporaryEmployee

Tier1 Tier2 Tier3 Union NonUnion Category1 Category2 Level 1:

Level 2:

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Type of Java Programs

• Application - two types

– Console-based program: Input and output are typically from/to the command prompt window

– Window-based program: User interaction (input and output) is performed by way of a graphical user interface (GUI)

• Applet

– Runs within a web browser (e.g., Microsoft Internet Explorer, Netscape, Mozilla, Opera)

– Requires an HTML page containing an Applet tag or Object tag that holds the information needed to invoke the applet – To view an applet use:

• Web browser or • JDK appletviewer