fun double(x: Int): Int {
    return 2 * x
}Copy

val result = double(2)Copy

fun double(x: Int = 4): Int {
    return 2 * x
}

double(2) // returns 4
double() // returns 8 (the default value is applied)Copy

fun foo(bar: Int = 0, baz: Int) : Int { /*...*/ }
val result = foo(baz = 4)Copy

class Person constructor(firstName: String) { /*...*/ }Copy

class Person(firstName: String) { /*...*/ }Copy

open class Base(p: Int)
class Derived(p: Int) : Base(p)Copy

public class WindowDto {
private Long id;
private String name;
private WindowStatus windowStatus;
private String roomName;
private Long roomId;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public WindowStatus getWindowStatus() {
        return windowStatus;
    }

    public void setWindowStatus(WindowStatus windowStatus) {
        this.windowStatus = windowStatus;
    }

    public String getRoomName() {
        return roomName;
    }

    public void setRoomName(String roomName) {
        this.roomName = roomName;
    }

    public Long getRoomId() {
        return roomId;
    }

    public void setRoomId(Long roomId) {
        this.roomId = roomId;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        WindowDto windowDto = (WindowDto) o;
        return Objects.equals(name, windowDto.name) &&
                Objects.equals(roomId, windowDto.roomId);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, name, windowStatus, roomName, roomId);
    }
}Copy

data class WindowDto(
    val id: Long,
    val name: String,
    val windowStatus: WindowStatus,
    val roomName: String,
    val roomId: Long
)Copy

enum class Direction {
    NORTH, SOUTH, WEST, EAST
}Copy

interface MyInterface {
    fun bar()
    fun foo() {
        // optional body
    }
}Copy

class Child : MyInterface {
    override fun bar() {
        // body
    }
}Copy

class HelloWorld {

    public String name(){
        return "Dev-Mind";
    }

    class A {
        public void hello(){
            System.out.println("Hello world" + name()); // Compilation error => method name() is not visible
        }
    }
}Copy

class HelloWorld {

    fun name() = "Dev-Mind"

    class A {
        fun hello() {
            println("Hello world" + name())
        }
    }
}Copy

public inline fun <T> Iterable<T>.find(predicate: (T) -> Boolean): T? {
    return firstOrNull(predicate)
}Copy

val guillaume = speakers.firstOrNull {
    it.firstname == "Guillaume"  // it is the current item in the collection
}

//  You can also write
val guillaume = speakers.firstOrNull { speaker ->
    speaker.firstname == "Guillaume"
}Copy

Speaker speaker = speakers.stream()
                          .filter(s -> s.getName().equals("Guillaume"))
                          .findFirst()
                          .orElse(null)Copy

class Cell(val content: String)

class Row(val cells: MutableList<Cell> = mutableListOf()) {
    // Define an Higher-Order Function
    fun cell(adder: () -> Cell): Row {
        cells.add(adder())
        return this
    }
}

class Table(val rows: MutableList<Row> = mutableListOf()) {
    // Define an Higher-Order Function
    fun row(adder: () -> Row): Table {
        rows.add(adder())
        return this
    }
}Copy

val table = Table()
    .row { Row().cell { Cell("Test") }}
    .row { Row().cell { Cell("Test2") }}Copy

fun main() {
    val morningNotification = 51
    val eveningNotification = 135

    printNotificationSummary(morningNotification)
    printNotificationSummary(eveningNotification)
}


fun printNotificationSummary(numberOfMessages: Int) {
    // Write the code here.
}Copy

You received 51 notifications
You received 99+ notifications

fun main() {
    val child = 5
    val adult = 28
    val senior = 87
    val oops = -1

    println("The movie ticket price for a person aged $child is $${ticketPrice(child)}.")
    println("The movie ticket price for a person aged $adult is $${ticketPrice(adult)}.")
    println("The movie ticket price for a person aged $senior is $${ticketPrice(senior)}.")
    println("The movie ticket price for a person aged oops is $${ticketPrice(oops)}.")
}

fun ticketPrice(age: Int): Int? {
    // Write the code here.
}Copy

The movie ticket price for a person aged 5 is $15.
The movie ticket price for a person aged 28 is $25.
The movie ticket price for a person aged 87 is $20.
The movie ticket price for a person aged oops is null.

fun main() {
    // Write the code here.
}


fun convertCurrency(
    amount: Double,
    initialCurrency: java.util.Currency,
    targetCurrency: java.util.Currency,
    conversionFormula: (Double) -> Double
) {
    val convertedAmount = String.format("%.2f", conversionFormula(amount)) // round the result to 2 decimal places
    println("$amount $initialCurrency can be changed in $convertedAmount $targetCurrency.")
}Copy

12.3 EUR can be changed in 12.92 USD.
12.3 USD can be changed in 11.69 EUR.

// Create a data class to represent the user profile here.
// Write the code here.

fun main() {
    val elodie = Profile("Elodie", 21, "Tennis", null)
    val eduardo = Profile("Eduardo", 22, "Tennis", elodie)

    listOf(elodie, eduardo).forEach{
        println("Name : ${it.username}")
        // Write the code here.
    }
}Copy

Name : Elodie
Age : 21
Hobby : like Tennis
Name : Eduardo
Age : 22
Hobby : like Tennis  with Elodie