Selenium Tutorial For Beginners 9|Java Variables and Operators|G C Reddy|

Java Tutorial for Beginners, Java Language Elements, Variables and Operators in Java Programming, What is Variable?, Declaration of variables in Java, Assign Values to Variables, Variable Naming Rules in Java, and Types Variables.
Java Local Variables, Instance Variables, and Class/Static Variables.
Java Arithmetic, Assignment, Comparison or Relational, and Logical Operators.

[gcreddy]

Class Notes:
Selenium Class 9: Java Variables, and Operators

i) Java Variables
ii) Java Operators

i) Java Variables

1) What is Variable?

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

Two types of memory in Computer Environment
a) Primary Memory (RAM)
b) Secondary Memory (ROM- CD, DVD, HDD, USB etc...)

2) Declaration of Variables

Java supports Explicit Declaration of Variables,

In Java;

dataType VariableName;
dataType Variable1Name, Variable2Name, Variable3Name;
dataType variableName= value;
dataType Variable1Name=value, Variable2Name=value, Variable3Name=value;

Example:
int a;
char b;
boolean c;
double d;
String e;
a=10;
b='X';
c= false;
d= 12.345;
e="Selenium Testing";

int f, g, h;
f=50; g=60; h=70;

int i=100;

int j=12, k=13, l=14;

3) Assign values to Variables

Two types of Assign values to Variables
a) Initialization
int a =100;
or
int b;
b=200;
b) Reading
Read Input (Using Input Devices)
Read from Files (Text/Excel/Database file...)
*Read from Application Objects

4) Variable naming Restrictions

a) Variables are case sensitive

in Java
int a;
int B;
a=100;
B=200;
System.out.println(A); //Incorrect
System.out.println(a); //Correct
System.out.println(B); //Correct
System.out.println(b); //Incorrect

Dim a
.
.
A=100
.
.
Msgbox a'100 (Correct Syntax)

b) Java Variable names should start with a letter or $ or _

Ex:
myvar
MYVAR
$myvar
_myvar
7myvar //Incorrect
*myvar //Incorrect
myvar7

c) Variable names should not match with Java Keywords and Reserved words

if, for, import, while,
true, Words)

int a;//Correct
int for; //Incorrect

d) Must be unique in the scope of declaration (No duplicate variables in a program)

e) Must not exceed 255 characters

Three types of variables in Java,

a) Local Variables
Local Variables are declared in methods, or blocks.

b) Instance Variables
Instance Variables are declared in a class but outside of a method or any block.
Instance variables are used by Objects to store their states.

c) Class / Static Variables
Static Variables are declared as static, these can’t be local

If you declare Instance variable before main method then it can be used before
main method only.

If you declare Instance variable after main method then it can be used after main
method only.

Example:
public class VariablesOperators {
static int a =10;

public int salary(){
int mySalary = 10000 +2000+1500;
mySalary = mySalary +a;
return mySalary;
}
public static void main(String[] args) {
//Static / Class Variable
int b=20; //Instance variable
System.out.println(b);//20
VariablesOperators obj= new VariablesOperators();
int e = obj.salary();
System.out.println(e);//13510

if (b>a){
int x=123;
System.out.println(a);//10
System.out.println(b);//20
System.out.println(x);//123
}
System.out.println(a);//10
System.out.println(b);//20

}
}

//Calling methods
obj.salary();
obj - Object
salary - Method

ii) Java Operators

Operators are used to perform Arithmetic, Comparison, and Logical Operations,

Categories of Java Operators,

a) Arithmetic Operators

b) Assignment Operators

c) Comparison Operators

d) Logical Operators

a) Arithmetic Operators

Arithmetic Operations,

Addition, Subtraction, Multiplication, Division, Modules, Exponentiation etc...

How to conduct Exponentiation in Java? -Jyothi

1) Addition + (Addition, String Concatenation)
int a=10, b=20;
int c = a+b; //Addition

String d = "Selenium";
String e = " Testing";
String f = d+e; //"selenium Testing"

2) Subtraction - (Subtraction, Negation)

int a=20, b=10;
int c = a-b;//10 (Subtraction)

int d = -100;//negation

3) Multiplication *

4) Division /

5) Modules %

6) Increment ++

7) Decrement --

Example:

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

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

System.out.println(a-b);//5
System.out.println(a*b);//50
System.out.println(a/b);//2
System.out.println(a%b);//0

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

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

}
}

b) Assignment Operators

1) Assignment =

2) Add and Assign +=

3) Subtract and Assign -=

4) Multiply and Assign *=

Example:

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

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

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

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

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

c) Relational / Comparison Operators

1) ==

2) !=

3) >

4) >=

5) <

6) <=

Note: Relational Operators return Boolean / Logical (true/false) Result

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









}
}