Selenium Tutorial 8: Java Variables and Operators

Java Variables and Operators tutorial explains Java Modifiers, Java Variables and Operators in Java. Types of Variables, Declaration of Variables, Naming restrictions and Assigning values to variables. Java Arithmetic, Relational, Assignment and Logical Operators. Java Access and Non Access Modifiers. Java Fundamentals for Selenium.

[gcreddy]

Class Notes:
Selenium Class 8: Java Variables and Operators.

i) Modifiers in Java

ii) Java Variables

iii) Java operators

i) Modifiers in Java

Modifiers are keywords that we add to those definitions to change their meaning.

a) Access Modifiers

b) Non-Access Modifiers

a) Access Modifiers

We use access modifiers to define access control for classes, methods and variables.

Four Access Modifiers

i) private

The private access modifier is accessible only within class.

Ex:

private int a =100;

2) default

If we don't specify any modifier then it is treated as default, this can be accessible only within package.

class Sample{
.
.
}

3) protected

The protected access modifier is accessible within package, outside of the package but through Inheritance only.

protected class Sample{
.
.
}

4) public

public access modifier is accessible everywhere.

public class Sample {
.
.
}

Modifier Within Class Within Package Outside of the package(by Sub class) Outside of the Package

private Y N N N

default Y Y N N

protected Y Y Y N

public Y Y Y Y

b) Non Access Modifiers

1) static

static modifier is used create classes, methods and variables.

Ex:

static int a =10;

static void int add(){
.
.
}

2) final

final modifier for finalizing of classes, methods and variables.

Ex:
final int a =100;
.
.
.
a=200; //Error

int a =100;
.
.
.
.
a =200;

3) abstract

abstract modifier is to create abstract classes, abstract methods

ex:

abstract class Sample{
.
.
}

ii) Java Variables

1) What is Variable?

A named memory location to store the temporary data within a program.

Two types of memories in Computer environment

a) Primary memory (RAM)

b) Secondary memory (HDD, DVD, USB drive etc...)

2) Declaration of Variables

Java supports Explicit declaration of Variables.

Syntax and Examples:

dataType variableName;

int a;

dataType variablename=value;

int b=20;

dataType variable1, Variable2, variable3;

int a, b, c;

dataType variable1=value; variable2=value; varible3=value;

int a=10; b=20; c=30;

3) Assign values to variables

a) Initialization

b) Reading

Ex:

int a=100; //Initialization

int a=10;
int b;
b=a; //Reading

4) Variable Naming Restrictions

> Java variables are case sensitive,

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

Ex:

myvar(Correct)
MYVAR
$myvar
_myvar
myvar_1

1myvar(Incorrect)
*myvar

> Variable names should not match with Java keywords/Reserved words.

> Must be unique in the scope of declaration.

> Variable names Must exceed 255 characters.


5) Types of Variables

Three types of variables in Java

a) Local variable
(Local variable is declared in methods or blocks.)

b) Instance variable
(Instance variables are declared in a class but outside of a method or any block)

c) Class/Static variable
A Variable that is declared as static, It cannot be local.

Example:

package xyza;

public class VariablesExample {
//a Variable is a Class/Static variable
static int a =100;

//mysalary variable is a Local variable.
public int salary(){
int mysalary =10000+2000+1500;
mysalary=mysalary + a;
return mysalary;
}

public static void main (String[]args){
//Instance variable
int b =200;
System.out.println(a);//100
System.out.println(b); //200

VariablesExample obj= new VariablesExample();

// i is a Local Variable
for (int i=1; i<=5; i++){
System.out.println(i);
System.out.println(a);
System.out.println(b);
}
}
}

iii) Java Operators

Important Categories of Operators

a) Arithmetic Operators

b) Relational Operators

c) Assignment Operators

d) Logical Operators

a) Arithmetic Operators

1) Addition + (for Addition, String concatenation)

2) Subtraction - (for Subtraction, Negation)

3) Multiplication *

4) Division /

5) Modules %

6) Increment ++

7) Decrement --

Example:

public class OperatorsExample {
public static void main (String [] args){
int a =10, b=5;
String c ="Selenium", d= "Testing";

System.out.println("Addition of a, b is: "+ (a+b));//Addition of a, b is: 15
of a, b is: "+ (a-b));
of a, b is: "+ (a*b));
System.out.println("Addition of a, b is: "+ (a/b));
System.out.println("Addition of a, b is: "+ (a%b));

b=10;
a = ++b;
System.out.println(a);//11

b=10;
a = --b;
System.out.println(a);//9
}
}

b) Relational Operators

1) ==

2) !=

3) >

4) >=

5) <

6) <=

Note: Relational Operators return Boolean / Logical result

Example:

public class OperatorsExample {
public static void main (String [] args){
int a =10, b=20;







}
}

d) Logical Operators

1) Logical Not Operator !

2) Logical And Operator &&

3) Logical Or Operators ||

Result Criteria

Not operator

Operand1 Operand2 Result

true true false
true false true
false true true
false false true

And operator

Operand1 Operand2 Result

true true true
true false false
false true false
false false false

Or Operator

Operand1 Operand2 Result

true true true
true false true
false true true
false false false

Example:

public class OperatorsExample {
public static void main (String [] args){
boolean a =true, b=false;
System.out.println(!(a && b));//true
System.out.println((a && b));//false
System.out.println((a || b));//true
}
}

public class OperatorsExample {
public static void main (String [] args){
int a =1000, b=500, c=7000;

if ((a>b) && (a>c)){
System.out.println("A is a Big Number");
}
else{
System.out.println("A is Not a Big Number");
}
}
}

c) Assignment Operators

1) Assignment Operator

=

a=10;

2) Add and Assign +=

3) Subtract and assign

4) Multiple and assign

Example:
public class OperatorsExample {
public static void main (String [] args){
int a =10;

System.out.println(a);//10
a+=10;
System.out.println(a);//20

a-=10;
System.out.println(a);//10

a*=10;
System.out.println(a);//100
}
}

Bitwise Operators

> Java defines several bitwise operators, which can be applied to the integer types, Bitwise operator works
on bits and performs bit-by-bit operation.

i) The bitwise & operator performs a bitwise AND operation.

ii) The bitwise ^ operator performs a bitwise exclusive OR operation.

iii) The bitwise | operator performs a bitwise XOR operation.

[nehasawai]

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[kumarrdy]

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[sumitmandhare]

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[AnuY-uu]

Awesome explanation.. nowhere will get. It will be helpful to many people. We are very much thankful to you sir

[namratasoni]

Very detail and clear concept of variables and operators.

[nareshbabu]

Hello sir good afternoon, The explanation for each and every point was really good. Thanks a lot for providing these kind of videos and notes for us. I thought of coping the notes in notepad but its not happening. I think until class 5 it has been provided. Could you please copy the the notes like you did for classes 1 to 5 for the remaining classes as well.

[amitgorain]

Sir, isn't instance variable is a variable which is declared outside any method(User-defined, Predefined)?
For example, if we initialize any variable lets say int a=10; outside of any method, then it can be accessible from any of the method.(If static method, then need to call the object using object of the class).
If I am declaring any variable inside any method irrespective of User-Defined, Predefined, it becomes local variable.
Please let me know if I am wrong!

[jeetujeetu]

Sir in last execution when we change the value b= 10
OK then increment a=++b value of a is 11
but now a=-- - b ans was 10
and then u wrote b=10 then a = 9
what was that please Clear it

[jeetujeetu]

Sir I am not getting that how b is instance variable.

[minnocentshreya]

How b is accessible inside for loop? Instance variable is accessed throughout the main method ?

[purushpandu]

a=--b;
System.out.println(a); output is 10 why you are projecting wrong scipts

[meghanaalluri]

Sir can you please provide the notes in comments section