Java 15 APIs & Features

/*
 * What are sealed classes in Java 15?
 * 
 * Sealed classes are a new feature that allows you to control which classes 
 * can extend or implement a type. They provide a way to define a closed 
 * hierarchy of classes, ensuring that only permitted classes can be subclasses.
 * This enables better domain modeling and improves pattern matching capabilities.
 */

// Define a sealed class hierarchy
public sealed class Shape 
    permits Circle, Rectangle, Triangle {
    
    public abstract double area();
}

// Permitted subclasses
public final class Circle extends Shape {
    private final double radius;
    
    public Circle(double radius) {
        this.radius = radius;
    }
    
    @Override
    public double area() {
        return Math.PI * radius * radius;
    }
}

public final class Rectangle extends Shape {
    private final double width, height;
    
    public Rectangle(double width, double height) {
        this.width = width;
        this.height = height;
    }
    
    @Override
    public double area() {
        return width * height;
    }
}

// Sealed interface
public sealed interface Vehicle 
    permits Car, Truck, Motorcycle {
    
    void start();
    void stop();
}

// Usage with pattern matching
public void processShape(Shape shape) {
    switch (shape) {
        case Circle c -> System.out.println("Circle: " + c.area());
        case Rectangle r -> System.out.println("Rectangle: " + r.area());
        case Triangle t -> System.out.println("Triangle: " + t.area());
        // No default needed - compiler knows all possibilities
    }
}

import jdk.incubator.vector.*;

// Vector operations for high-performance computing
public class VectorExample {
    static final VectorSpecies<Float> SPECIES = FloatVector.SPECIES_PREFERRED;
    
    public static void vectorAdd(float[] a, float[] b, float[] c) {
        int i = 0;
        int upperBound = SPECIES.loopBound(a.length);
        
        for (; i < upperBound; i += SPECIES.length()) {
            FloatVector va = FloatVector.fromArray(SPECIES, a, i);
            FloatVector vb = FloatVector.fromArray(SPECIES, b, i);
            FloatVector vc = va.add(vb);
            vc.intoArray(c, i);
        }
        
        // Handle remaining elements
        for (; i < a.length; i++) {
            c[i] = a[i] + b[i];
        }
    }
    
    public static float vectorSum(float[] array) {
        FloatVector sum = FloatVector.zero(SPECIES);
        int i = 0;
        int upperBound = SPECIES.loopBound(array.length);
        
        for (; i < upperBound; i += SPECIES.length()) {
            FloatVector va = FloatVector.fromArray(SPECIES, array, i);
            sum = sum.add(va);
        }
        
        float result = sum.reduceLanes(VectorOperators.ADD);
        
        // Handle remaining elements
        for (; i < array.length; i++) {
            result += array[i];
        }
        
        return result;
    }
}