Interfaces

        
          // Interface definition
interface Drawable {
    void draw();
    default void setColor(String color) {
        System.out.println("Setting color to " + color);
    }
}

interface Resizable {
    void resize(double factor);
    boolean canResize();
}

// Class implementing multiple interfaces
class Rectangle implements Drawable, Resizable {
    private double width, height;
    private String color;

    public Rectangle(double width, double height) {
        this.width = width;
        this.height = height;
        this.color = "Black";
    }

    @Override
    public void draw() {
        System.out.println("Drawing rectangle: " + width + "x" + height);
    }

    @Override
    public void setColor(String color) {
        this.color = color;
        System.out.println("Rectangle color set to " + color);
    }

    @Override
    public void resize(double factor) {
        width *= factor;
        height *= factor;
    }

    @Override
    public boolean canResize() {
        return true;
    }
}

// Polymorphism in action
public class GraphicsDemo {
    // Method accepting interface type
    public static void renderShape(Drawable shape) {
        shape.draw();
        shape.setColor("Blue");
    }

    public static void resizeIfPossible(Resizable resizable, double factor) {
        if (resizable.canResize()) {
            resizable.resize(factor);
            System.out.println("Resized by factor: " + factor);
        }
    }

    public static void main(String[] args) {
        Rectangle rect = new Rectangle(10, 5);

        // Polymorphic behavior
        renderShape(rect);        // Drawable behavior
        resizeIfPossible(rect, 2.0); // Resizable behavior

        // Array of interfaces
        Drawable[] shapes = new Drawable[] {
            new Rectangle(5, 3),
            new Circle(4)
        };

        for (Drawable shape : shapes) {
            shape.draw();
        }
    }
}

// Functional interface (Java 8+)
@FunctionalInterface
interface Calculator {
    int calculate(int a, int b);
}

class MathOperations {
    public static void main(String[] args) {
        // Lambda expressions
        Calculator add = (a, b) -> a + b;
        Calculator multiply = (a, b) -> a * b;
        Calculator subtract = (a, b) -> a - b;

        System.out.println("5 + 3 = " + add.calculate(5, 3));
        System.out.println("5 * 3 = " + multiply.calculate(5, 3));
        System.out.println("5 - 3 = " + subtract.calculate(5, 3));

        // Method reference
        Calculator power = MathOperations::powerOfTwo;
        System.out.println("2^3 = " + power.calculate(2, 3));
    }

    private static int powerOfTwo(int base, int exponent) {
        return (int) Math.pow(base, exponent);
    }
}