What are Java Variables and Data Types?

1. What is a Java Variable?

A variable can be called a container that holds some value in a Java program. The variable has assigned a data type that defines what type of value the variable can hold. The variable has a name which locates in the memory. 

If you want to use a variable in a program, there are two steps associated with it you have to perform:
  • Variable Declaration
  • Variable Initialization

i. Variable Declaration
While declaring a variable you have to assign a data type with the variable name. The variable name has to be unique.

Example: String employee;

ii. Variable Initialization
It means assigning a value to the declared variable.

Example: employee = "John"

The above two steps (declaration and initialization) can also be joined together in one single step.

Example: String employee = "John";

Let's explain the above example, 
  • 'String' is a data type
  • 'employee' is the name of the variable
  • "John" is the value assigned to a variable named employee.

2. Types of Java Variables

Java has three types of variables:
  1. Local Variables
  2. Instance Variables
  3. Static Variables

2.1. Local Variables

A variable that is declared inside a method is a local variable. These variables can only be used within that method as their scope lies only inside that method.

2.2. Instance Variables

A variable that is declared outside of the method but inside the class is called the instance variable. It is not declared static.

2.3. Static Variables

A variable that is declared with the keyword 'static' and outside the method is called a static variable. Static variables are allocated memory when a class is loaded in memory. Static variables are initialized before instance variables.

Code example for Java Variable Types:

package com.techlistic.java;

public class JavaVaribales {
 // Instance Variables
 int x = 15;
 // Static Variables
 static String message = "Hello World!";
 // Main Method
 public static void main(String[] args) {
  // Local variables
  int a = 10; 
  int b = 20;
  // Some code here
  // ---------
  // ---------
 // Method
 void myMethod() {

  // Local Variables
  char ch = 'i';
  float num = (float) 1.5;



3. Java Data Types

As we already discussed in the previous tutorial every Java variable has a data type. Data type tells us the different sizes and values that can be stored in a variable.

Java has two Data Types:
  1. Primitive Data Types
  2. Non-Primitive Data Types

3.1. Primitive Data Types

Primitive data types are built-in within Java language. No additional methods are required for it. There are 8 primitive data types:
  1. byte
  2. short
  3. int
  4. long
  5. float
  6. double
  7. boolean
  8. char

Data TypeDefault ValueDefault size
byte01 byte
short02 bytes
int04 bytes
long0L8 bytes
float0.0f4 bytes
double0.0d8 bytes
booleanfalse1 bit
char'\u0000'2 bytes
1. byte : 
Its value range lies between -128 to 127. Byte is used in place of int to save memory as a byte is 4 times smaller than an integer. Its default value is 0.

byte x = 10;
byte y = 20;

2. short
The range of short data type lies between -32,768 to 32,767. The short data type can again be used to save memory instead of int. Short is 2 times smaller than int. Its default value is 0.

short s = 12000;
short t = -10000;

3. int
int is also known as an integer. Its range value lies between -2,147,483,648 to 2,147,483,647. Its default value is 0. This is the most commonly used data type for integral values.

int x = 10;
int y = 2000;

4. long
The long data type is 8 bytes. Its value range lies between -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807. long data type is used when a large range of values is required which are not provided by int. Its default value is 0.

long l = 100000L;
long m = -300000L;

5. float :
The float data type is used for decimal values. Its range is unlimited. float is recommended over double data type to save memory. Its default value is 0.0F.

float f = 20.5f;

6. double :
double data type is generally used for decimal values just like float. Its range is unlimited. Its default value is 0.0d.

double d = 10.5;

7. boolean :
The boolean data type can only store one of the two values: true or false.

boolean flag = false;
boolean isJavaInteresting = true;

8. char :
The char data type is used to store characters. The character must be within single quotes ('a').

char grade = 'A';

3.2. Non-Primitive Data Types

Non-Primitive data types are not defined by Java and are created by programmers except Strings. Unlike primitive, non-primitive data types can be null. Non-Primitive data types are:
  1. Strings
  2. Arrays
  3. Classes
  4. Interface etc.
i. Strings :
The String data type is used to store the sequence of characters or text. Strings must be declared within double quotes like "Hello".

String myName = "John"; 

Also, read - Java Tutorials Series

Next >>  Java Modifiers

Vaneesh Behl
Passionately writing and working in Tech Space for more than a decade.

Follow Techlistic

YouTube Channel | Facebook Page | Telegram Channel | Quora Space
Feel free to ask queries or share your thoughts in comments or email us.


Popular posts from this blog

17 Best Demo Websites for Automation Testing Practice

Mastering Selenium Practice: Automating Web Tables with Demo Examples

Automation Practice: Automate Amazon like E-Commerce Website with Selenium

14 Best Selenium Practice Exercises for Automation Practice

How to Automate Google Search with Selenium WebDriver

Top 10 Highly Paid Indian CEOs in the USA

Python Behave Tutorial: A Comprehensive Guide to Behavior-Driven Development (BDD)

Selenium IDE Tutorial: How to Automate Web Testing with Easy-to-Use Interface

What is Robot Class in Selenium WebDriver?

Top 51 Most Important Selenium WebDriver Interview Questions