Java session2

Internet Technologies

Jigar Jobanputra

What is JAVA?

Java is platform

Java is a language

Features of JAVA

Simple

Object-Oriented

Platform Independent

Secured

Robust

Architecture Neutral

Portable

High Performance

Distributed

Multi-threaded

Simple

Java is a simple in the sense of :- Syntax based on C++(So easier for programmers to learn it after

C++)

Removed many confusing and/or rarely-used features e.g. explicit

pointers, operator overloading etc.

No need to remove unreferenced object because there is

Automatic Garbage Collection in JAVA.

Object-Oriented

Object-Oriented means we organize our software as a

combination of different types of objects that incorporates

both data and behavior

Object-Oriented Programming (OOPs) is a methodology that

simplify software development and maintenance by providing

some rules

Basic concepts of OOPs are: Object

Class

Inheritance

Polymorphism

Abstraction

Encapsulation

Platform Independent

A platform is a hardware or software environment in which a

program runs. There are two types of platforms software-based

platform. The java platforms differs from most other platforms

in the sense it’s a software-based platform that runs on top of

other hardware-based platforms. It has two components Runtime Environment

API(Application Programming Interface)

Cont..

Java Code can be run on multiple Platforms e.g. Windows,

Linux, Sun Solaris , Mac OS etc. Java Code is Complied by the

compiler and converted into bytecode. This bytecode is a

platform independent code because it can be run on multiple

platforms.

Secured

Java is secured because: No explicit pointer

Programs runs inside virtual machine sandbox.

Robust

Robust Simply Means strong. Java uses strong memory

management.

There are lack of pointers that avoids security problem.

There is automatic garbage collection.

There is exception handing and type checking mechanism in

java. All these points makes java robust.

Architectural Neutral

There is no implementation dependent features.

Portable

We can carry java bytecode to any platform.

High Performance

Java is faster than traditional interpretation since bytecode is

“Close” to native code still somewhat slower than a compiled

language (e.g. C++)

Distributed

We can create distributed applications in java. RMI and EJB are

used for creating distributed applications. We may access files

by calling the methods from any machine on the internet.

Multi-threaded

A thread is like a separate program executing concurrently.

We can write java programs that deal with many tasks at once

by defining multiple threads.

The main advantage of multi-threading is that it shares the

same memory.

Thread are important for multi-media, web applications etc.

Primary reason for the popularity of java

Java is platform independent

Java provides applets and servlets for use on the web.

Java is an object-oriented programming language.

Java is easy.

Compilation of C Program

Compilation of JAVA program

Tell Me Difference?

What is bytecode?

Machine-independent code generated by the JAVA compiler

and executed by the java interpreter

The executable form of Java code that executes within the java

virtual machine(VM). Also called interpreted code, and p-code.

Bytecode is a term which has been used to denote various

forms of instruction sets designed for efficient execution by a

software interpreter as well as being suitable for further

compilation into machine code.

Points to remember

Java is not just programming language; it is also platform.

The java programming language works only on the java

platforms.

The java virtual machine enables the same java application to

be used on heterogeneous platform.

The application are compiled into bytecode, which are

interpreted on the native platform at runtime.

Object Oriented programming is about identifying various data

types from the real world, and the kind of interactions that are

supported by those data types.

Object oriented programming supports the concepts of data

encapsulations, inheritance, and polymorphism.

First program of JAVA

class Hello

{

public static void main(String args[])

{

System.out.println(“Hello World”);

}

}

Note: Filename and public classname should be same….

Next step to run JAVA program

Go to command prompt (Run->cmd.exe)

Set directory to your working directory where you have saved

your file (C:\myprog)

C: (To change current drive to c if you are working on other

drive)

cd myprog (to change drive to myprog)

javac Hello.java (Compile Program)

java Hello (run program (make sure to run using class name))

Software required to run java program

JDK

JRE

JDK (JAVA DEVELOPMENT KIT)

The java development kit (JDK) is an implementation of either

one of Java SE, Java EE, or Java ME platforms released by

oracle corporation in the form of a binary product aimed at java

developers on Solaris, Linux, Mac OS x or Windows.

On 17th November 2006, sun announced that it would be

released under GNU (General Public License), thus making it

free software. This happened in large part on 8 may 2007, when

sun contributed the source code to the openJDK.

JDK VERSIONS

JDK Alpha and Beta(1995)

JDK 1.0 (January 23, 1996)

JDK 1.1 (February 19, 1997)

J2SE 1.2 (December 8,1998)

J2SE 1.3 (May 8, 2000)

J2SE 1.4 (February 6,2002)

J2SE 5.0 (September 30, 2004)

JAVA SE 6 (December 11, 2006)

JRE (JAVA RUNTIME ENVIORNMENT)

A java virtual machine is a program which executes certain other

programs, namely those containing java bytecode instructions.

JVM are most often implemented to run on an existing operating

system, but can also be implemented to run directly on hardware.

A JVM provides a run-time environment in which java bytecode

can be executed, enabling features such as automated exception

handing, which provides root-cause debugging information for

every software error.

A JVM is distributed along with Java class Library, a set of

standard class libraries (in java bytecode) that implement the java

application programming interface(API). This libraries , bundled

together with the JVM, from the Java Runtime Environment (JVM)

Assignment

Explain how platform independence is achieved in java

Explain the concept of data encapsulation, inheritance and

polymorphism in object oriented programming language

Define Bytecode

List and explain the features of java

Why java is so popular

How many different types of program can be created in java?

Explain in detail

Java session2

Education

Transcript of Java session2