Data Types And Variables In Java

    
  Java Application/Uses

Desktop Applications or standalone Applications such as acrobat reader, media player, antivirus etc.

Web Applications (Web Applications are those applications which runs on server and you can create dynamic application using jsp,servlet,struts etc.

Enterprise Applications such as banking applications, insurance   etc.

Mobile Application (Android Apps)

Robotics, Games.

    Software Tools.

Big Data technologies.

Data Types in Java

 Data types are used to store different values in the variable. There are two types of data types:

Primitive data types: which include Integer, Character, Boolean, and Floating Point.

Data Type	Default Value	Default size
char	'\u0000'	2 byte
byte	0	1 byte
short	0	2 byte
int	0	4 byte
long	0L	8 byte
float	0.0f	4 byte
double	0.0d	8 byte
boolean	false	1 bit

Non-primitive data types: which include Classes, Interfaces, and Arrays.

Variables:

Variable means whose value can be changed.

Variable contains value which is stored in memory and holds some space.

Every Variable is assigned a datatype which shows size(4 byte,8 byte etc.) and type of data type(int,double etc.)

2 steps to use variables

·        Variable Declaration

·        Variable Initialization

Variable Declaration

Syntax: 

Datatype variablename;

Eg: int x;

Where int is the data type and x is the variable name.

Variable Initialization

Syntax:

Datatype variablename=value;

Eg: int x=89;

Where int is the data type, x is the variable name and 89 is the value which assigned to x.

Types of variables

In Java, there are three types of variables:

1.  Local Variables

2.  Instance Variables

3.  Static Variables

1) Local Variables

The variables which are declared inside the body of a method is called as local variables.

2) Instance Variables

Instance variables are a variable that are declared outside a method and inside a class.

static keyword is not required to declare a instance variable

3) Static Variables

Static variables are initialized only once, at the start of the program execution.

A variable that is declared as static is called static variable.

static keyword is required to declare a static variable.

These variables should be initialized first, before the initialization of any instance variables.

Example:

class Demo{  

  string name=”LearningPoint92”;   //instance variable  

  static int x=100;        //static variable 

   void display ()

     {  

    int y=90;  //local variable  

}  

      }