Java Variables

Java Variables
 

1) What is Variable?
A named memory location to store or hold the data.

There are two types of memory in Computer environment:

i) Primary memory -RAM

ii) Secondary memory -ROM
Ex: CD, DVD, HDD etc...

Note: Variables store in primary memory.
-------------------------
2) Declaration of Variables in Java.
Java Supports explicit declaration of variables

Syntax:

dataType VariableName;

Ex:

int a;
---------------
dataType variable1, variable2, variable3;

Ex:

int a, b, c;
------------------------
dataType VariableName = value;

Ex:

int a =100;
--------------------------
3) Assigning values to variables
a) Initialization

int a;
a=10; // Initialization
--------------
int a=10; // Initialization
----------------
b) Reading
    using Input devices
    from files(text/excel)
    from databases
    from Application objects
-------------------------
4) Types of Variables
a) Instance Variable
A variable that is declared inside the class but outside the method

b) Local variable


A variable that is declared inside the method

c) Static variables
A Variable that is declared as static, It cannot be local.
----------------------
5) Naming Conventions
> Java Variables are case sensitive, monkey is not the as Monkey or MONKEY.

char monkey, Monkey, MONKEY

> Java variable name must start with a letter or $ or _

Ex:
myvar
MYVAR
$myvar
_myvar
myvar1
myvar_1
----------
1myvar - invalid
----------------------
> Variable names cannot be equal to java reserved words

Ex:

int
for
import

> Must be unique in the scope of declaration.
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6) Java Variables Declaration Example:
 

package JavaExamples;

public class VariablesExamples {

    public static void main (String [] args){
        // dataType variableName;
        int a;
        a = 10;
        // dataType VariableName = Value;
        int b = 20;
        // Declaration of multiple variables in a statement
        int c, d, e;
        c =30;
        d =40;
        e = 50;
        // Declaration of multiple variables and assigning values
        int f=60, g=70, h=90;
        int j;
        j = a; // Reading
        char x ='A';
        double y = 2.3456;
        String z = "Selenium";
       
        System.out.println (a);
        System.out.println (b);
        System.out.println (c);
        System.out.println (d);
        System.out.println (e);
        System.out.println (f);
        System.out.println (g);
        System.out.println (h);
        System.out.println (x);
        System.out.println (y);
        System.out.println (z);
        System.out.println (j);
    }
}
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Also Read:



Java Operators 

Java Conditional Statements 

Java Loop Statements

Java Arrays 

Java Methods

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