Session 1 - Tp 1 6u6l48

Session 1 Introduction to Java

Objectives         

Explain the history of Java Explain Java in brief List the types of Java programs List Java Capabilities Differentiate between applets and applications Explain the Java Virtual Machine (JVM) List the features of some IDEs Examine the JDK and tools under it Analyze future trends and technologies Java Simplified / Session 1 / 2 of 32

Introduction to Java  

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Introduced in 1995 by Sun Microsystems Its objective was to develop a software for embedding in consumer electronic devices. Initially called „Oak‟ Internet s had problems of portability and platform independence. Java being secure, portable, and platform independent was found to be capable of addressing large scale problems across the Internet. Java Simplified / Session 1 / 3 of 32

What is Java?   

An object-oriented programming language A cross platform language It is used to create stand-alone applications, net based programs and consumer devices programs. 

Example : cellular phones, palm pilots

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Java and the Internet 

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Programs on the net are either static or dynamic. Applets helps to develop dynamic programs. Applets run on a Java enabled web browser. Applets can respond to input and actions.

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Security issues 

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An Applet has to be ed on the ‟s system before it can work.

This can be a potential risk for the ‟s system. Hence, applets are restricted from accessing all areas of the disk. Java Simplified / Session 1 / 6 of 32

Security issues Contd… 

The control is exercised by the

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JVM generates byte codes as a result of compilation Byte codes cannot be executed without the JVM

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Features in Java2 

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Swing: new set of classes and interfaces used to create an advanced GUI Drag and Drop: interactively transfers information across different applications. Also transfers information interactively from one part of a program‟s interface to another.

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Features in Java2 Contd… 

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Java 2D API: set of classes for advanced 2D graphics and imaging Java Sound: totally new set of features pertaining to Java‟s audio features RMI: Remote Method Invocation allows applications to call objects located at remote sites and communicate with them Java Simplified / Session 1 / 9 of 32

Types of Java Programs 

Applets 

Programs created specially to work with the Internet

Displays an image

GUI to accept input Java Simplified / Session 1 / 10 of 32

Types of Java Programs Contd… 

Console applications 

Java programs that run from a command prompt and do not display any GUI screen

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Types of Java Programs Contd… 

GUI Applications: Java programs that run stand-alone and accept input through a GUI based screen.

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Types of Java Programs Contd… 

Servlets 

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Suitable for web based n-tier application development

Client sends request which is processed by the server The server side APIs extend capabilities of standard APIs and are known as Servlets Also called server side applets Example – HTML form processing, processing databases and performing server side transactions Java Simplified / Session 1 / 13 of 32

Types of Java Programs Contd… 

Packages  

Class libraries in Java Programmers can create their own packages or use the built-in packages 

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java.awt, java.io and java.applet are some examples

Database applications  

Uses JDBC API for database connectivity Programs can be either applets or application

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What can we do with Java? 

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Create a wide variety of applications from a simple computation program to complex distributed application One can develop:   

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Colorful scrolling banner for web pages Interactive quizzes A program that plays audio, displays a banner and animates images at the same time Interactive games that can run as stand alone or be deployed on the web Java Simplified / Session 1 / 15 of 32

Difference between Applets and Applications Applets

Applications 

Do not need a browser to execute

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These run within JVM

Executed in a java compatible web browser Applets load and run on a Java-enabled web browser

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Difference between Applets and Applications Contd… Applets

Applications 

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Manages its own flow of execution No restrictions about reading or writing from/to the local file system

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Flow of execution is partly managed by the browser context Cannot read/write from/to the local file system

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Similarities in Applets and Applications 

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Both need to use the standard Java class libraries Both can use the Abstract Windowing Toolkit (AWT)

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Java Virtual Machine (JVM) 

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Has an interpreter component that enables communication between Java byte code and a computer‟s operating system Java code can run on any platform by using JVM JVM normally reads and executes Java statements one at a time JVM is responsible for platform independence and small size compiled code Recognizes only a particular binary format called a class file Java Simplified / Session 1 / 19 of 32

Visual Development Tools 

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Helps in quick and efficient development of Java applications and applets Simplifies the software development process Includes class browser for viewing and navigating through the class hierarchy Includes a source code editor that helps code programs

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Some Visual Development Tools 

Visual Age for Java from IBM 

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Borland Jbuilder from Borland/Inprise 

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Works with existing databases, applications and transactions

Includes an integrated editor, debugger, compiler, visual designer, wizards and sample applications

Forte for Java, Community Edition from Sun Microsystems 

Integrated visual design, editing, compilation and debugging capabilities to create applets and applications Java Simplified / Session 1 / 21 of 32

Java Development Kit (JDK) 

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Contains the software and tools needed to compile, debug and execute applets and applications A set of command line tools Three major releases are:   

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Java 1.0 – first release Java 1.1 – 1997 release Java 1.4.2 – latest release

Freely available at Sun‟s official website Java Simplified / Session 1 / 22 of 32

Tools under JDK 

javac: compiler used to compile Java source code 

Syntax: javac [option] source Source files ends with an extension of .java

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Options include:

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-classpath -d -g -o -verbose Java Simplified / Session 1 / 23 of 32

Tools under JDK Contd… 

java: interpreter used to execute Java byte codes  

java [option] classname [arguments] Options can include  

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-classpath -Dname name -help -v or –verbose -X

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Tools under JDK Contd… 

appletviewer: Used to view and test applets 

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Syntax: appletviewer [options] url

javadoc: This is the Java documentation tool 

Generates detailed documentation in HTML form for any .java source code or package

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New Features of Java 1.4.2 

Improved  

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Compiling Speeds Divisions of integers and floating point numbers

Provides to IE and Netscape for redirecting URLs New I/O Class added Few bugs have been removed in AWT

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New Features of Java 1.4.2 Contd… 

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A new class to provide endless for mouse wheel scrolling. s the standard Microsoft Windows XP appearance as default when running on Windows XP platform. Indeterminate progress bars have been added. JTabbedPane displays a single, scrollable run of tabs. A spinner is a single line input field that lets the select a number or an object value from an ordered set.

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Present Java Technologies 

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Creation and deployment of applications that can run on any operating system for distributed computing in the form of features such as RMI Database management in the form of JDBC Reusable software components in the form of JavaBeans

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Present Java Technologies Contd… 

Java 2 Enterprise Edition (J2EE) which includes:

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Future trends 

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New products in the area of embedded technologies for consumer devices by making use of mobile computing. Miniature devices such as Palm pilots and mobile phones are equipped with a features such as email, gaming options and many others. They are based upon Java 2 Micro Edition (J2ME). Java Simplified / Session 1 / 30 of 32

Summary  

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Java was introduced by Sun Microsystems in 1995. Java is a programming language popularly used to build programs that can work on the Net. Its primary features are that it is object-oriented and a cross platform language. Swing, Drag and Drop, Java 2D API, Java Sound and RMI are some of the features added to the existing version of Java. A Java applet is designed to work in a pre-defined “sandbox” only. This makes it safe to be used on the Internet. Java bytecodes are machine language instructions understood by the Java Virtual Machine and usually generated as a result of compiling Java language source code. Java Simplified / Session 1 / 31 of 32

Summary Contd… 

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Java programs can be divided into following categories - applets, applications, GUI applications, servlets and database applications. Java visual development tools help to develop Java applications and applets more quickly and efficiently. The JDK contains the software and tools needed to compile, debug and execute applets and applications written in the Java language. It‟s basically a set of command-line tools. Enhancement in Swing, AWT, a new I/O class and so on has been added in the latest version of Java 1.4.2. The future will use a lot of Java related programs for consumer gadgets with embedded technologies. Java Simplified / Session 1 / 32 of 32