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What is static Keyword in Java?

The static keyword is used to create class-level members, meaning:

• They belong to the class rather than an instance (object)
• They are shared among all objects of the class
• Can be accessed without creating an object

Static Variables

A static variable is shared across all instances of the class.

    
    class Counter {
        static int count = 0;  // static variable

        Counter() {
            count++;
            System.out.println("Count: " + count);
        }
    }

    public class Main {
        public static void main(String[] args) {
            new Counter(); // Count: 1
            new Counter(); // Count: 2
            new Counter(); // Count: 3
        }
    }
    
    

Note: The value of count is shared and incremented across all objects.

Static Methods

• Belong to the class, not an instance
• Can be called without an object
• Cannot access non-static members directly

    
    class MathUtils {
        static int square(int x) {
            return x * x;
        }
    }

    public class Main {
        public static void main(String[] args) {
            System.out.println(MathUtils.square(5));  // Output: 25
        }
    }
    
    

Inside static methods, you cannot use this or call non-static methods/fields directly.

Static Blocks

Static blocks are used to initialize static variables. They run once when the class is first loaded.

    
    class App {
        static int configValue;

        static {
            System.out.println("Static block running...");
            configValue = 42;
        }
    }

    public class Main {
        public static void main(String[] args) {
            System.out.println(App.configValue);  // Triggers static block
        }
    }
    
    

Output:

    
    Static block running...
    42
    
    

Summary Table

Feature	Description
static variable	Shared across all instances
static method	Belongs to class, no object needed
static block	Executes once when class is loaded

When to Use static

Use Case	Example
Shared config/constants	static final double PI = 3.14;
Utility/helper methods	Math.sqrt(), Collections.sort()
Class-level logic	Counters, cache management, ID generators

"static makes things belong to the class itself, not any individual object."

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