1fun main() {
2    val numbers = listOf(1, 2, 3, 4, 5)
3    val squares = numbers.map { it * it }
4    println(squares)
5}

 1data class Person(val firstName: String, val lastName: String)
 2
 3fun main() {
 4    val people = listOf(
 5        Person("Alice", "Smith"),
 6        Person("Bob", "Jones"),
 7        Person("Alice", "Johnson")
 8    )
 9
10    val nameCount = people.groupingBy { it.firstName }.eachCount()
11    println(nameCount)
12}

 1import java.math.BigDecimal
 2
 3data class Product(val name: String, val price: BigDecimal)
 4data class OrderLine(val product: Product, val quantity: Int)
 5
 6fun main() {
 7    val orders = listOf(
 8        OrderLine(Product("Laptop", BigDecimal("1200.00")), 2),
 9        OrderLine(Product("Mouse", BigDecimal("25.50")), 3)
10    )
11
12    val totalPrice = orders.fold(BigDecimal.ZERO) { acc, line ->
13        acc + (line.product.price * line.quantity.toBigDecimal())
14    }
15
16    println(totalPrice)
17}

 1fun String.toCamelCase(): String =
 2    this.split(" ")
 3        .filter { it.isNotBlank() }
 4        .mapIndexed { index, word ->
 5            if (index == 0) word.lowercase()
 6            else word.lowercase().replaceFirstChar { it.uppercase() }
 7        }
 8        .joinToString("")
 9
10fun main() {
11    val input = "Hello world"
12    println(input.toCamelCase())
13}

1enum class Square { EMPTY, HIT, MISS }
2
3fun main() {
4    val battleship = listOf(Square.HIT, Square.HIT, Square.HIT)
5    val isSunken = battleship.all { it == Square.HIT }
6    println(isSunken)
7}

 1fun main() {
 2    val sentences = listOf(
 3        "Java runs on the JVM",
 4        "Kotlin also runs on the JVM"
 5    )
 6
 7    val distinctWords: List<String> = sentences
 8        .flatMap { it.split(Regex("\\s+")) }
 9        .filter { it.isNotBlank() }
10        .map { it.lowercase() }
11   		.distinct()
12    println(distinctWords)
13}