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Jayashree
Jayashree

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Static vs Non-Static Variables in Java – Complete Guide (With Example)

#beginners #programming #java #tutorial

One of the most common confusions for Java beginners is understanding the difference between static and non-static variables.

In this blog, we’ll cover:

  • Types of variables in Java
  • What is a static variable?
  • What is a non-static variable?
  • A real-time example
  • Memory behavior
  • Interview-ready explanation

Let’s get started

Types of Variables in Java

  • Java mainly has three types of variables:

Local Variable

  • Declared inside a method, constructor, or block
  • Accessible only within that method
  • Destroyed once the method execution ends

Example:

public void display() {
    int x = 10;   // Local variable
}
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Static Variable (Class Variable)

  • Declared using the static keyword
  • Belongs to the class, not the object
  • Only one copy is shared among all objects

Non-Static Variable (Instance Variable or Object Variable)

  • Declared inside a class but outside any method
  • Belongs to an object
  • A separate copy is created for each object

Example Program

public class Institute {

    static String name = "Payilagam"; // static variables
    static String address = "Velachery";

    String course_name; // Non-static variables
    int course_fees;
    String class_duration;

    public static void main(String args[]) {

        System.out.println(Institute.name);
        System.out.println(Institute.address);
        System.out.println();

        Institute java = new Institute();
        java.course_name = "Java";
        java.course_fees = 23000;
        java.class_duration = "3 Months";

        Institute python = new Institute();
        python.course_name = "Python";
        python.course_fees = 22000;
        python.class_duration = "2 Months";

        System.out.println("Course Name: " + java.course_name);
        System.out.println("Course Fees: " + java.course_fees);
        System.out.println("Course Duration: " + java.class_duration);

        System.out.println();

        System.out.println("Course Name: " + python.course_name);
        System.out.println("Course Fees: " + python.course_fees);
        System.out.println("Course Duration: " + python.class_duration);
    }
}
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Static Variable Explained

static String name = "Payilagam";
static String address = "Velachery";
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Key Points:

  • Belongs to the class
  • Only one copy exists in memory
  • Shared by all objects
  • No need to create an object to access it

Accessing Static Variables:

Inside the same class, a static variable can be accessed in two ways:

System.out.println(name);           // Works
System.out.println(Institute.name); // Also works
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Both are valid. However, using the class name is considered a good practice.

Why?

  • It clearly shows that the variable belongs to the class, not to an object.
  • It improves code readability.
  • It avoids confusion with local or instance variables.
  • It follows Java coding standards.

Best Practice:

Always access static variables using:

ClassName.variableName
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Even though both ways work, using the class name makes your code cleaner and more professional.

Non-Static Variable Explained

String course_name;
int course_fees;
String class_duration;
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Key Points:

  • Belongs to the object
  • Each object has its own copy
  • Requires object creation to access

Example:

Institute java = new Institute();
java.course_name = "Java";
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Memory Concept (Important for Interviews)

Static Variables:

  • Loaded into memory when the class is loaded
  • Only one copy exists

Non-Static Variables:

  • Loaded into memory when an object is created
  • Each object has its own copy

Real-Life Analogy

Institute Name → Common for all courses → Static
Course Details → Different for each course → Non-Static

  • If data is common → Use static
  • If data is unique per object → Use non-static

Interview One-Line Answer

A static variable belongs to the class and is shared by all objects, while a non-static variable belongs to an object and each object has its own separate copy.

Conclusion

Use static variables when the data is common across all objects.
Use non-static variables when the data should be unique for each object.

Understanding this concept clearly will strengthen your foundation in Java and OOPS.

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