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Basics-Of-Java

This document provides an overview of programming languages and Java. It discusses programming methodologies like procedural, structured, and object-oriented programming. It then covers the history and evolution of programming languages including the development of Java. The rest of the document details features of Java like being portable, secure, and object-oriented. It describes the Java Virtual Machine architecture and how a basic Java program works. Finally, it discusses editions of Java like Java SE, Java EE, and Java ME.

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INDEX • Programming methodologies • Language Development • Why Programming Language & Evolution of Languages. • History Of Java • Why Only Java ? • What is Java ? • Where Java is Used in the industry ? • Flavors of Java • Features Of Java • Architecture Of JVM • A Basic Java program & its internal details
PROGRAMMING METHODOLOGIES Deals with two elements: 1. Data – memory 2. Functions - code Programming Standards Unstructured Programming Procedural Methodology Structured Programming Object Oriented Programming Two Techniques 4 Features Inheritance Polymorphism Abstraction Encapsulation Object Based P/L Any one feature of OOPs but not all. Eg: VB
LANGUAGE DEVELOPMENT – BUILDING BLOCKS For Natural Languages Noun Words Sentences Paragraphs etc Literals Pronoun For Programming Languages Lexical Tokens Statements Program Strings Keywords Identifiers Operators Grammar Syntax - rules Logic To Solve Problem (48) Unary Binary Ternary
DATATYPES & ASSOCIATED KEYWORDS void Lexical Tokens Boolean Character Integer Floating Point float 4B Double 8B Long double 10B Char 2B deprecated Byte 1B short 2B int 4B long 8B boolean True false 6 14 Decimal points
Electronic Devices Microprocessors Before Computer Technology introduction Machine & Assembly Languages Drawbacks Code Complexity Difficult to understand Procedure Oriented Methodology Drawbacks Complexity cant be handled No Security For Data Any part of memory can be accessed First Computer Languages High Level Languages Ex: C, Fortran, Pascal, Cobol Object Oriented Methodology EVOLUTION OF LANGUAGES & BIRTH OF OOPS Languages Ex: C++, Java, C#, ABAP  A P/L is used to develop Applications to simplify user tasks.  The Central Theme of any P/L is to Store, manipulate and retrieve data.
HISTORY OF JAVA Bill Joy – Wrote “Further” Patrick Naughton – Green Project James Gosling – OAK (Frustration on C++) Sun Announced Java in a Major Conference 1995 1970 - 1990 1983 1991 Time Line Releases Classes Packages 1996 Java 1.0 (JDK 1.0) 212 8 1998 Java 1.2 1548 64 2004 Java 1.4 (SDK 1.4) 2006 Java 1.5 3562 166 2008 Java 1.6 Major Releases:
WHAT IS JAVA JAVA Programming Language Platform Technology JVM API Class Files Design Runs Java is a multi dimensional software entity and defined as below.  Programming Lang --- It is a Third Generation P/L like C, C++, Fortran, C#, VC++ etc. It is capable to work with internet inside electronics and supports database.  Technology ---- Java is a Technology pertaining to Database, Electronics and Enterprises.  Platform ---- It is a S/W or H/W environment in which a program gets executed. Java acts as a platform between Operating System & Application Software.
FEATURES OF JAVA  Simple  Object Oriented  Network Supported  Secured  Portable  Robust  Platform Independent / Architecture Neutral  Dynamic  High Performance  Multi – Threaded  Interpreted Simple – It is designed to write bug free code easily. Generally, bugs related to memory allocation and garbage collection are reduced than in C and C++. Object Oriented – Data is represented in terms of Objects( gives security to data). Objects have state(data) and behavior(methods). Implements all OOP’s features. Secured – Secure execution of code. OS too doesn’t understands the byte code. JVM only executes it. Malicious code over network can be executed securely. Robust – JVM is developed free of bugs. Handling of exceptions to prevent crashing of system and prohibiting the introduction of viruses by checking the byte code.
High Performance – Java Byte codes can be complied on the fly using JIT compiler. Faster Execution on Programs. Memory never runs out. Multi – Threaded – A single program can have different processes executing independently and continuously. It makes java robust as processes doesn’t gets extra CPU cycles and malicious code execution is prevented. Dynamic(ly linked) – No Explicit linking in java. When other classes are referenced, compiler searches them in local system and they are linked. Portable – Source code written on one machine can work on multiple machines having different Operating Systems and configurations. Platform Independent - An executable code generated on one machine can work on multiple machines having different Operating system and related JVM of that OS. Byte Code Executable code (Given to JVM) JVM (passes to OS) UNIX OS Hardware C/C++ Executable code (given to OS) UNIX OS (OS executes over H/W) Hardware JVM Windows OS Hardware Windows Operating System Hardware Fails cant give to H/w
ARCHITECTURE OF JVM – JAVA VIRTUAL MACHINE Method Area Stack Area Heap Area PC Registers Native Method Stack Native Method API Class Loader Sub System Execution Engine • JVM is a Specification , Implementation & Runtime Instance for a java program to run. • It is a specification given by Sun Micro Systems and implemented by various Vendors and can come into existence only when Java application is executed.
Class Loader Sub System – bytecode is loaded through class loader. It uses classpath. Method Area – It stores all the compiled instructions Stack Area – It contains the memory space for respective methods and their local variables. Every method call will be stored in Stack. Heap Area – Objects are stored. PC Registers – Program Counter – It contains the information about the next executable instruction Native Method Stack & Native Method API – Working with C/ C++ methods in java. We use the native API. Execution Engine - It loads, links and initializes memory spaces with values. Creates objects through memory spaces.
OOPS AND ITS FEATURES OOP’s is not a programming language. It is just a concept which has 4 features. 1. ENCAPSULATION – Binding of Data and Functions(methods) into one single unit. 2. ABSTRACTION – Providing various levels of hiding over Encapsulated data and functions. This is used to provide security to our application. 3. POLYMORPHISM – Multiple behaviors of data and functions. 4. INHERITANCE – It is the ability to re – use the data and functions of one encapsulation for another encapsulation.  A Programming language which supports all the four features is known as “ Object Oriented Programming Language”. Ex: C++, Java, C# etc.  If Any language supports at least one but not all four is known as “ Object Based P/L”. Ex: VB.
DEVELOPMENT OF JAVA PROGRAMS Develop Source Code Execute using “java” command Compile it using “javac” command Save with .java extension JAVA API Using Using An Editor Notepad/ Editplus Install the Latest JDK Set Environment Variables Permanently CLASSPATH – Class Files & Bytecode location PATH – OS uses to get java resources JVM runs this not OS. JVM uses OS for I/O. OS uses Hardware. .class is generated which contains Bytecode Compiler Interpreter
EDITIONS / FLAVORS OF JAVA JAVA JAVA ME JAVA SE JAVA EE Standard Edition Micro Edition Enterprise Edition Stand Alone / Desktop Based Applications Large Scale Enterprise Applications, Web Servers Consumer Device applications for mobiles, PDA, pagers etc.