Java Journeys : Variables

What are Variables ?

Variables are like storage units in a java program and are used to store different kinds of data like numbers (integers, decimals), characters (letters), boolean values(true/false) and references to objects.

source : GIPHY

Declaring Variables

Declaring a variable in java means specifying its data type and name.

public class variables {
 public static void main(String[] args) {
  
 //Declaring variables
  int count;
 }  
 }

We’re simply informing the compiler that a variable with a certain name and type exists. However, declaring a variable doesn’t allocate any value.

Variable Initialization

Initialization is the process of assigning an initial value to a variable. Creating a variable involves both declaring it and allocating memory for it, possibly initializing it with a value.

public class variables {
 public static void main(String[] args) {
  
 //Intializing variables
  int count = 100;     
 }  
 }

Naming Rules

Naming rules for variables contribute to the overall quality, readability, and maintainability of software code.

1. Must start with a letter(a-z,A-Z), underscore(_) or dollar sign($).

2. Case Sensitive : Uppercase & lowercase letters are considered different.

3. Java Keywords cannot be used : (int, double, if, else etc can’t be used).

4. Following the first character, variable names can include letters, digits (0–9), underscores, and ($).43

Variable Types

Primitive Variable Type

Primitive variables store simple values directly in memory. They represent basic data types in Java.

public class variables {
 public static void main(String[] args) {
  
 //Primitive Variable types
  int num = 100;
  double salary = 100.5;
  char grade = 'A';
  boolean isBool = true;    
    
 }  
 }

Reference Variable Type

Reference variables store memory addresses (references) of objects.

public class variables {
 public static void main(String[] args) {
  
 //declare reference variable to type String
  String name;

 //Assign a string object to reference variable
  name = "Test";
  
 }  
 }

In above example:

• We declare a reference variable named name of type String.
• We assign the String object "Test" to the reference variable name.

Conclusion

To sum up the above, Variables act as containers for storing and managing data within a program. They are categorized into two primary types: primitive types, responsible for directly holding basic values, and reference types, which store memory references to objects.

Thankyou and Happy Coding !! 😊