Introduction & History Of JAVA

• The most prominent use of computers is to solve problems quickly and accurately.
• The solution adopted to solve a problem is provided as a sequence of instructions or specifications of activity which enables a user to achieve the desired result.

Software Applications

• The solution for solving a problem in the field of information technology is achieved by developing software applications.
• A software application can be defined as a collection of programs that are written in high-level programming languages to solve a particular problem.

Programming Languages

• The development of software application is done using a programming language.
• A programming language is used as a medium for communicating the instruction to the computer.
• The programming language enforces a particular style of programming that is referred to as a programming paradigm.

There are 2 types of Programming Languages

1. STRUCTURED PROGRAMMING
2. OBJECT ORIENTED PROGRAMMING (OOP)

Structure Programming

• In structured programming paradigm, the application development is decomposed into a hierarchy of subprograms.
• The subprograms are referred to as procedures, functions, or modules in different structured programming languages.
• Each subprogram is defined to perform a specific task.
• Some of structured programming languages are C, Pascal, and Cobol.

Following figure displays bank application activities broken down into subprograms:

• Main disadvantage of structured programming languages are as follows:
  • Data is shared globally between the subprograms.
  • Efforts are spent on accomplishing the solution rather than focusing on problem domain.
• This often led to a software crisis, as the maintenance cost of complex applications became high and availability of reliable software was reduced.

Object-Oriented Programming

• Growing complexity of software required change in programming style.
• Some of the features that were aimed are as follows:
  • Development of reliable software at reduced cost.
  • Reduction in the maintenance cost.
  • Development of reusable software components.
  • Completion of software development with the specified time interval.
• These features resulted in the evolution of object-oriented programming paradigm.
• In object-oriented programming paradigm, applications are designed around data, rather than focusing only on the functionalities.

Following shows different activities involved in the object-oriented software development:

• Object-oriented Analysis (OOA) phase determines the functionality of the system.
• Object-oriented Design (OOD) phases determines the process of planning a system in which objects interact with each other to solve a software problem.
• Object-oriented Programming (OOP) deals with the actual implementation of the application.

An OOP language is based on certain principles that are as follows:

• Object – Represents an entity which possesses certain features and behaviors.
• Class – Is a template that is used to create objects of that class.
• Inheritance – Enables the developer to extend and reuse the features of existing classes and create new classes. The new classes are referred to as derived classes.
• Polymorphism – Is the ability of an object to respond to same message in different ways.
• Encapsulation – Is a mechanism that combines data and implementation details into a single unit called class.
• Abstraction – Is a design technique that focuses only on the essential features of an entity for a specific problem domain.

History

• Team of engineers from Sun Microsystems wanted to design a language for consumer devices.
• Project was named as ‘Green Project’.
• Team included: James Gosling, Mike Sheridan, and Patrick Naughton.
• Java was developed in 1991 in Sun MicroSystems.
• Efforts were taken to produce portable and a platform independent language that can run on any machine.
• A Program or a software is implemented on different operating system that’s actually called Platform independent.
• Result was evolution of Java.
• Initially called ‘OAK’ and later renamed to Java.

In 1995,

• Internet and Web started emerging and was used worldwide.
• Sun Microsystems turned Java into an Internet programming language.
• It emerged as a Web technology that added dynamic capabilities to the Web pages.

In 2009 / 2010,

Sun Microsystems was acquired by Oracle Corporation.

Some Important Points About Java Programming Language

• It is one of the most popular OOP language.
• It helps programmers to develop wide range of applications that can run on various hardware and Operating System (OS).
• It is also a platform that creates an environment for executing Java application. JRE – JAVA RUNTIME ENVIRONMENT
• It caters to small-scale to large-scale problems across the Internet.
• Java applications are built on variety of platforms that range from:
  • Embedded devices to desktop applications
  • Web applications to mobile phones
  • Large business applications to supercomputers

JAVA IS EVERYWHERE (SLOGAN)

• WRITE ONCE, RUN EVERYWHERE (WORE)
• JAVA resides in mobiles, client machines, server machines, embedded devices, smart phones etc

Java Virtual Machine (JVM)

• It is an executable engine that creates an environment for executing Java compiled code, that is, bytecode.
• It is known as a virtual machine because it is an imitation of a Java processor on the physical machine. 
• There are different implementations of JVM available for different platforms, such as Windows, Unix, and Solaris.

ByteCode

• Is an intermediate form closer to machine representation.
• Is an optimized set of instructions executed by the Java runtime environment (JRE)
• This environment is known as JVM.
• The same bytecode can be executed by different implementations of JVM on various platforms.