Java-11-To-Java-17-Upgrade

// Old: Traditional data class
public class Person {
    private final String name;
    private final int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String name() { return name; }
    public int age() { return age; }

    @Override
    public boolean equals(Object obj) { /* boilerplate */ }
    @Override
    public int hashCode() { /* boilerplate */ }
    @Override
    public String toString() { /* boilerplate */ }
}

// New: Record (Java 16+)
public record Person(String name, int age) {
    // Compact constructor for validation
    public Person {
        if (age < 0) throw new IllegalArgumentException("Age cannot be negative");
    }

    // Custom methods can be added
    public boolean isAdult() {
        return age >= 18;
    }
}

// New: Sealed class hierarchy
public sealed class Shape
    permits Circle, Rectangle, Triangle {

    public abstract double area();
}

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;
    }
}

public non-sealed class Triangle extends Shape {
    // Non-sealed allows further inheritance
    private final double base, height;

    public Triangle(double base, double height) {
        this.base = base;
        this.height = height;
    }

    @Override
    public double area() {
        return 0.5 * base * height;
    }
}

// Old: Traditional instanceof with casting
public String processObject(Object obj) {
    if (obj instanceof String) {
        String str = (String) obj;
        return str.toUpperCase();
    } else if (obj instanceof Integer) {
        Integer num = (Integer) obj;
        return "Number: " + num;
    } else if (obj instanceof List<?>) {
        List<?> list = (List<?>) obj;
        return "List with " + list.size() + " elements";
    }
    return "Unknown type";
}

// New: Pattern matching for instanceof (Java 16+)
public String processObject(Object obj) {
    if (obj instanceof String str) {
        return str.toUpperCase();
    } else if (obj instanceof Integer num) {
        return "Number: " + num;
    } else if (obj instanceof List<?> list) {
        return "List with " + list.size() + " elements";
    }
    return "Unknown type";
}

// Works great with sealed classes
public String describeShape(Shape shape) {
    if (shape instanceof Circle circle) {
        return "Circle with radius " + circle.radius();
    } else if (shape instanceof Rectangle rect) {
        return "Rectangle " + rect.width() + "x" + rect.height();
    } else if (shape instanceof Triangle triangle) {
        return "Triangle with base " + triangle.base();
    }
    return "Unknown shape";
}

// Old: Traditional switch statement
public String getDayType(DayOfWeek day) {
    String result;
    switch (