fboeller

class Builder {
  String firstName;
  String lastName;
  int age;

  public Builder firstName(String firstName) {
    this.firstName = firstName;
    return this;
  }

fboeller

class Person {
  final String firstName;
  final String lastName;
  final int age;

  Person(String firstName, String lastName, int age) {
    Objects.requireNonNull(firstName);
    Objects.requireNonNull(lastName);
    this.firstName = firstName;
    this.lastName = lastName;

fboeller

fun diameter(shape: Shape): Double = when (shape) {
  is Rectangle -> Math.sqrt(shape.x * shape.x + shape.y * shape.y)
  is Circle -> 2 * shape.radius
  is Parallelogram -> /* Math */
}

fboeller

fun area(shape: Shape): Double = when (shape) {
  is Rectangle -> shape.x * shape.y
  is Circle -> PI * shape.radius * shape.radius
  is Parallelogram -> shape.side * shape.height
}

fboeller

fun perimeter(shape: Shape): Double = when (shape) {
  is Rectangle -> (shape.x + shape.y) * 2
  is Circle -> 2 * PI * shape.radius
  is Parallelogram -> (shape.base + shape.side) * 2
}

fboeller

sealed class Shape
class Rectangle(val x: Double, val y: Double) : Shape()
class Circle(val radius: Double) : Shape()
class Parallelogram(val base: Double, val height: Double): Shape()

fboeller

fun diameter(shape: Shape): Double = when (shape) {
  is Rectangle -> Math.sqrt(shape.x * shape.x + shape.y * shape.y)
  is Circle -> 2 * shape.radius
}

fboeller

fun area(shape: Shape): Double = when (shape) {
  is Rectangle -> shape.x * shape.y
  is Circle -> PI * shape.radius * shape.radius
}

fboeller

fun perimeter(shape: Shape): Double = when (shape) {
  is Rectangle -> (shape.x + shape.y) * 2
  is Circle -> 2 * PI * shape.radius
}

fboeller

interface Shape {}

class Rectangle implements Shape {
  double x, y;
}

class Circle implements Shape {
  double radius;
}