Java for Selenium Part 3

Java Data Types, Modifiers and Variables

i) Java Data Types

ii) Java Modifiers

iii) Java Variables
i) Java Data Types

What is Data Type?

Data Type is a classification of the type of data that a Variable or Constant or Method can hold in computer program.

Ex: character, integer, float, boolean etc...

Java supports Explicit declaration of data types.

(We need to specify the data type before declaring Variables or Constants or Methods with return value.)


dataType variableName;
dataType variableName = value;
dataType variable1Name, variable2Name, variable3Name;
dataType variable1Name=value; variable2Name=value, variable3Name=value;
final dataType constantName = value;
accessModifier dataType(int) methodName(int parameter1, int parameter2){
Two types of Data Types in Java,

a) Primitive Data Types

b) Non-Primitive Data Types/Reference Data types
a) Primitive Data Types (8 data types)

1) Integer Types

i) byte (8 bits)(-127 to 128)


byte a =10;

ii) short (16 bits)

short b = 1000;

iii) int (32 bits)

int c =1000000;

iv) long (64 bits)

long d =1000000000000000000;

2) Relational Types
(Numbers with decimal places)

v) float (32 bits)

float x =1.23;

vi) double (64 bits)

double y = 123.4567898;
3) Characters

vii) char

char z ='A';
char e = '1';

d) Conditional

viii) boolean

boolean x = true/false;
b) Non-Primitive Data Types/Reference Data types
Non-Primitive Data Types or Reference Data types in Java are Objects and Arrays


Classname objectName = new ClassName();
Convert Data from one type to another.

Two types of Value Assignment for Variables

i) Initialization

int a=100; //Initialization

int b;
b=200; //Initialization

ii) Reading

1) Read using Input devices
2) Read from Files etc...

Note: If you read data (any type) then computer program considers the data as String type data,
if you to perform mathematical operations then we need to convert the data.

Note: We can't convert Alpha bytes to integers or float or double.
ii) Modifiers in Java

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

Two types of Modifiers in Java

a) Access Modifiers

b) Non Access Modifiers
a) Access Modifiers

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

1) public

public access modifier is accessible everywhere.


public class Sample {

2) private

The private access modifier is accessible only within class.


private int a =123;

3) default

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

class Sample{

4) protected

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


protected class Sample{
b) Non Access Modifiers

1) static

static modifier is used to create classes, methods and variables.


static int add(){

static int a =10;
2) final

final modifier for finalizing classes, methods and variables.


final int x =123;
x=234; //Incorrect
int x =123;
x=234; //Correct

3) abstract

abstract modifier is used to create abstract classes and abstract methods.


abstract class Sample{
iii) 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 - HDD, DVD, USB drive etc...)
2) Declaring Variables

Java supports Explicit declaration of Data Types only.


int a=10, b=20;
int res = a + b;//Correct
int a=10;
int res = a + b; //Incorrect
int a=10, b;
int res = a + b; //Incorrect

public static void main(String[] args) {
int a;
int b=100;

int c, d, e;
int f=1, g=2, h=4;
char k ='1';
char l ='A';
char m='a';
//char n ='ad';//Incorrect

double y =234.456789;

boolean z = true;

String myTool = "Selenium";
String t = "Test Automation using Selenium";
3) Assign Values to Variables

a) Initialization

int a=100;

b) Reading (Reading using Input devices, from files)

int a, b;
4) Variables Naming Restrictions
a) Java Variables are Case sensitive.

int a;
int B;

Dim a
A =100
Msgbox a //Correct
b) Java variable names should start with a letter or $ or _

7myvar //Incorrect
*myvar //Incorrect
c) Variable names should not match with Java keywords / Reserved word

int a; //Correct
int new; Incorrect
d) Must be unique in the scope of declaration

e) Must not exceed 255 characters
5) Types of Variables
a) Local Variables
Local Variables are declared in methods or blocks (Conditions, Loops etc...)

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

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

> The static variable gets memory only once in a class area at the time of class loading.

It makes our program efficient (i.e it saves memory)

public int salary(){
int mySalary = 10000 + 2000 + 1500 + a;
return mySalary;

public static void main(String[] args) {
int b=20;

if (b > a){
int x=123;
System.out.println("B is a Big Number");
System.out.println(a); //Static variable
System.out.println(b); //Instance Variable
System.out.println(x); //Local Variable


Java for Selenium Part 4 Link


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