Class 1 Java introduction

What is Java

Java is a programming language and a platform.

Java is a high level, robust, secured and object-oriented programming language.

Platform: Any hardware or software environment in which a program runs, is known as a platform. Since Java has its own run time environment (JRE) and API, it is called platform.

Features of Java

The Java Features given below are simple and easy to understand.

1. Simple
2. Object-Oriented
3. Portable
4. Platform independent
5. Secured

Object-oriented Java is Object-oriented programming language. Everything in Java is an object. Object-oriented means we organize our software as a combination of different types of objects that incorporates both data and behavior. Basic concepts of Oops are: Object Class Inheritance Polymorphism Abstraction Encapsulation Variable Variable is name of reserved area allocated in memory. In other words, it is a name of memory location. It is a combination of "vary + able" that means its value can be changed. Ex. int data=50;//Here data is variable  Types of Variable There are three types of variables in java: local variable instance variable static variable 1) Local Variable A variable declared inside the method is called local variable. 2) Instance Variable A variable declared inside the class but outside the method, is called instance variable . It is not declared as static. 3) Static variable A variable which is declared as static is called static variable. It cannot be local. class A{   int data=50;//instance variable   static int m=100;//static variable   void method(){   int n=90;//local variable   } }//end of class   Data Types in Java Data types represent the different values to be stored in the variable. In java, there are two types of data types: Primitive data types Non-primitive data types Object in Java An entity that has state and behavior is known as an object . Class in Java A class is a group of objects which have common properties. It is a template or blueprint from which objects are created. It is a logical entity. It can't be physical. A class in Java can contain: fields methods constructors blocks nested class and interface class <class_name>{       field;       method;   }   Method in Java In java, a method is like function i.e. used to expose behavior of an object. Advantage of Method Code Reusability Code Optimization Java Keywords The following list shows the reserved words in Java. These reserved words may not be used as constant or variable or any other identifier names. abstract assert boolean break byte case catch char class const continue default do double else enum extends final finally float for goto if implements import instanceof int interface long native new package private protected public return short static strictfp super switch synchronized this throw throws transient try void volatile while Java naming conventions for identifiers 1. Use CamelCase for most identifiers (classes, interfaces, variables, and methods). 2. Use an initial capital letter for classes and interfaces, and a lower case letter for variables and methods. 3. For named constants, use all capital letters separated by underscores. 4. Avoid using $ characters in identifiers. Java Package A java package is a group of similar types of classes, interfaces and sub-packages. Package in java can be categorized in two form, built-in package and user-defined package.