Static & Final Keywords

The static Keyword

static means the member belongs to the class rather than to any specific instance.

Static Variables

Shared across all instances of the class.

class Counter {
    static int count = 0; // Shared by all Counter objects
    
    Counter() {
        count++;
    }
}

Static Methods

Can be called without creating an object.

class MathUtils {
    static int add(int a, int b) {
        return a + b;
    }
}

// Usage
int result = MathUtils.add(5, 3); // No object needed!

Static Blocks

Executed once when the class is loaded.

class Database {
    static {
        System.out.println("Database driver loaded");
    }
}

[!IMPORTANT] Static methods cannot access instance variables or call instance methods directly!

The final Keyword

final means "cannot be changed."

Final Variables (Constants)

final double PI = 3.14159;
// PI = 3.14; // ERROR! Cannot reassign

Final Methods

Cannot be overridden by subclasses.

class Parent {
    final void display() {
        System.out.println("Cannot override me!");
    }
}

Final Classes

Cannot be inherited.

final class Utility {
    // No one can extend this class
}

Combining static and final

class Constants {
    public static final double PI = 3.14159;
    public static final String APP_NAME = "MyApp";
}

Quiz