Java Fundamentals - Java Introduction

1. Java History

Key Facts

Father of Java: James Gosling
Java introduced at: Sun Microsystems
Java was originally called: Oak
First public implementation: Java 1.0 in 1995
Core principle: Write Once, Run Anywhere (WORA)

The source notes describe Java as an object-oriented programming language with a runtime environment. It combines features associated with C and C++ with additional concepts and is suitable for standalone as well as web application development.

2. What is Java?

Java is an object-oriented programming language developed by Sun Microsystems and released in 1995.
James Gosling initially developed Java at Sun Microsystems, which was later merged with Oracle Corporation.
Java is described in the source as having its format from C and OOP features from C++.
Java programs are platform independent: the same compiled program can run on different operating systems when the appropriate Java runtime is available.
The ability to write code once and run it on different platforms is commonly summarized as WORA — Write Once, Run Anywhere.

3. Object-Oriented Paradigm

The primary objective of the object-oriented technique is to eliminate some flaws encountered in the procedural approach.

OOP treats data as a critical element and uses objects and methods to organize and protect that data.

Object: The source illustration represents an object as containing data and methods, with methods surrounding/operating on the data.

4. Major Objectives of Object-Oriented Programming

The emphasis is on the data rather than the procedures.
Methods that operate on data are tied together in a data structure.
Programs are divided into small instances called objects.
Data remains hidden and cannot be accessed directly by external functions.
Objects may communicate with each other through methods.
Programs follow the bottom-up approach.
New data and methods can be added whenever necessary.

5. Basic Terms and Features of OOP

Classes & Objects

Represent the structure and instances of an object-oriented program.

Data Abstraction

Expose essential behavior while hiding implementation details.

Data Encapsulation

Wrap data and the methods that operate on it together.

Inheritance

Allows a class to acquire features from another class.

Polymorphism

Allows one interface or operation to have multiple forms.

Dynamic Binding

Connects an overridden method call with its implementation at runtime.

Composition

Builds complex objects by combining other objects.

6. Advantages of OOP

Code recycle and reuse.
Wrapping up of data into a single unit.
Easy to partition project work based on objects.
Message passing between objects makes interface descriptions with external systems more straightforward.
Software complexity can be handled and managed more easily.
Objects in a problem domain can be mapped into a program.
Data hiding is possible.
Inheritance can eliminate redundant code.

7. Java Features

Feature	Description
Platform Independent	The same `.class` bytecode can work on different operating systems with a suitable Java runtime.
Simple	The source describes Java as small and familiar to C and C++ programmers.
Object Oriented	Focuses on data and the interface to it through objects.
Distributed	Supports applications that operate across networked systems.
Portable	Java programs are designed to move between platforms with minimal platform-specific changes.
Interpreted	Java bytecode is executed by the Java runtime.
High Performance	JIT (Just-In-Time) compilation improves runtime performance.
Multithreaded	Supports execution of multiple threads.
Dynamic	Java supports dynamic loading and runtime linking concepts.

8. Types of Java Applications

1. Standalone Applications

A Java application designed without a client-server architecture is called a standalone application.

2. Distributed Applications

A Java application designed on the basis of a client-server architecture is called a distributed application.

The source notes associate distributed application development with the J2EE / Java EE platform.

9. Java Details

Item	Details from the Source
Home / Vendor	Sun Microsystems (later Oracle Corporation)
Author	James Gosling
Objective	To prepare simple electronic consumer goods
Project	Green
First Version	JDK 1.0 (January 23, 1996)
Type	Open Source Software, as stated in the source notes

The PDF contains version references that are historical/course-note specific. The table preserves the information as presented in the source.

10. Java Introduction Details

Java introduction details and Core Java technologies diagram

The source's Java introduction page identifies James Gosling as author, Sun Microsystems as vendor, Green Project as the project name, Oak as the initial name, Java as the present name, and WORA as the slogan/motto.

Item	Source Information
Author	James Gosling
Vendor	Sun Micro System (later merged into Oracle Corporation)
Project Name	Green Project
Type	Open source & free software
Initial Name	OAK language
Present Name	Java
Extensions	.java, .class & .jar
Initial Version	JDK 1.0
Present Version in Source	J2SE 8 / 2014
Operating System	Multi Operating System
Implementation Language	C, C++
Objective	To develop web applications
SUN	Stanford University Network
Slogan / Motto	WORA — Write Once, Run Anywhere

11. Importance of Core Java

According to the source notes, Java is used in a wide range of applications and technologies.

Desktop applications such as media players and antivirus applications.
Web applications.
Enterprise applications such as banking applications.
Mobile applications.
Embedded systems.
SmartCards.
Robotics.
Games.

Core Java Ecosystem Mentioned in the Source

Webservices, Hadoop, Selenium, Android, Cloud Computing, ADF, EJBs, Spring, Hibernate and Struts are shown around Core Java in the source diagram.

12. Parts of Java

The source states that, according to Sun Microsystems, the Java language/platform is divided into three parts:

Part	Full Form
J2SE / JSE	Java 2 Standard Edition
J2EE / JEE	Java 2 Enterprise Edition
J2ME / JME	Java 2 Micro Edition

13. JDK Includes

Tool	Purpose
`javac`	Java Compiler
`java`	Java Interpreter / launcher
`javap`	Java Disassembler
`javah`	Used for C-language header files in the source notes
`javadoc`	Creates HTML documentation
`jdb`	Java Debugger

14. Java Program Start to END Flow

The source flow chart shows the basic path:

Text Editor

→

Java Source Code

→

javac

→

Java Class File

→

Java

→

Output

The diagram also shows javah leading to header files and the Java class file leading to the debugger path.

15. Tokens

The smallest logical unit in Java programming is called a lexeme. A collection of lexemes belonging to a particular group is called a token.

Example

int a = b + c * d;

Lexemes: int, a, =, b, +, c, *, d, ;

Types of Tokens

Identifiers

Names assigned to programming elements.

Literals

Constant values assigned or used in programs.

Keywords / Reserved Words

Predefined words recognized by Java.

Operators

Symbols that perform operations on operands.

16. Identifiers

An identifier is a name assigned to programming elements such as variables, methods, classes, abstract classes and interfaces.

int a = 10;

Element	Meaning
`int`	Data type
`a`	Variable / identifier
`=`	Operator
`10`	Constant / literal
`;`	Terminator

17. Literals

A literal is a constant value represented directly in a Java program.

Literal Type	Examples
Integer / Integral	byte, short, int, long → 10, 20, 30...
Character	`'A'`, `'B'`...
Floating Point	float → 10.22f; double → 11.123
Boolean	`true`, `false`
String	`"abc"`, `"def"`...

18. Number Systems in Java

Programming languages use number systems to represent numbers. The source lists four common number systems.

Binary

Base 2

Octal

Base 8

Decimal

Base 10

Hexadecimal

Base 16

19. Keywords / Reserved Words

The source defines a keyword as a predefined word having recognition and internal functionality. It also distinguishes reserved words as predefined words reserved by the language.

Examples mentioned: goto, const.

Keyword Categories

Category	Examples
Data Types / Return Types	byte, short, int, long, float, double, char, boolean, void
Access / Other Modifiers	public, protected, private, static, final, abstract, native, volatile, transient, synchronized, strictfp
Flow Controllers	if, else, switch, case, default, for, while, do, break, continue, return
Class / Object Related	class, enum, extends, interface, implements, package, import, new, this, super
Exception Handling	throw, throws, try, catch, finally

20. Operators

An operator is a symbol that performs a particular operation over the provided operands.

Operator Type	Operators
Arithmetic	`+ - * / % ++ --`
Assignment	`= += -= *= /= %=`
Comparison	`== != < > <= >=`
Boolean / Logical	`& \| ^`
Bitwise / Shift	`& \| ^ << >>`
Short-Circuit	`&& \|\|`
Ternary	`Expr1 ? Expr2 : Expr3`

21. Java Comments

Single-Line Comment

Starts with two forward slashes.

// This is a comment

Multi-Line Comment

Starts with /* and ends with */.

/*
 * This is a
 * multi-line comment
 */

Documentation Comment

The source gives the following author documentation format.

/**
 * @author smamilla
 */

22. Java Statements

A statement is a collection of expressions. Java statements are instructions that tell the programming language what to do.

Examples

double entryFee = 15.75;
int a = 12;

Different Types of Statements

General Purpose Statements
Declaring variables, methods and classes
Creating objects and accessing variables and methods
Conditional statements
Iterative statements
Transfer statements
Exception handling statements
Synchronized statements

23. Quick Revision

Topic	Key Point
Father of Java	James Gosling
Original Name	Oak
First Public Java	Java 1.0 in 1995
WORA	Write Once, Run Anywhere
OOP	Uses objects, data and methods to structure programs.
OOP Features	Classes & Objects, Abstraction, Encapsulation, Inheritance, Polymorphism, Dynamic Binding, Composition.
Java Features	Platform independent, simple, object-oriented, distributed, portable, interpreted, high performance, multithreaded and dynamic.
Application Types	Standalone and distributed applications.
JDK Tools	javac, java, javap, javah, javadoc, jdb.
Tokens	Identifiers, literals, keywords/reserved words and operators.
Number Systems	Binary, Octal, Decimal and Hexadecimal.
Comments	Single-line, multi-line and documentation comments.
Statements	Instructions such as declarations, conditionals, loops, transfers, exception handling and synchronization.