Static and Non-Static Variables in Java

Non-Static Variables

• In Java, variables are used to store data. Based on how memory is allocated and how values are shared, variables can be static or non-static (instance).
• Understanding this difference is important for writing efficient and well-structured programs.

Non-Static (Instance) Variables

A non-static variable is declared inside a class but outside any method, without using the static keyword. Each object of the class gets its own separate copy of the variable.

Key Points

• Created when an object is created
• Each object has a different value
• Stored in heap memory
• Accessed using object reference

Example

class Student {
    int marks;
}

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student();
        Student s2 = new Student();

        s1.marks = 80;
        s2.marks = 90;

        System.out.println(s1.marks); // 80
        System.out.println(s2.marks); // 90
    }
}

• Here, marks is a non-static variable, so each Student object has its own value.

Static Variables
A static variable is declared using the static keyword. It belongs to the class, not to individual objects. Only one copy of a static variable exists, shared by all objects of the class.

Key Points

• Created once when the class is loaded
• Shared among all objects
• Stored in method area
• Accessed using class name (recommended)

Example

public class Employee {
        String name;
    int salary;
    static String company_name ="TCS";

    public static void main(String[] args)
    {

    Employee mukesh = new Employee();
    mukesh.name = "Mukesh kumar";
    mukesh.salary = 10000;

    Employee hari = new Employee();
    hari.name = "Hari krishnan";
    hari.salary = 20000;
    }
}