package helloWorld fun main(args: Array) { println("Hello World!") }
equals()
hashCode()
toString()
public class Customer { private String name; private String email; private String company; public Customer(String name) { this(name, "", ""); } public Customer(String name, String email) { this(name, email, ""); } public Customer(String name, String email, String company) { this.name = name; this.email = email; this.company = company; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public String getCompany() { return company; } public void setCompany(String company) { this.company = company; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Customer customer = (Customer) o; if (name != null ? !name.equals(customer.name) : customer.name != null) return false; if (email != null ? !email.equals(customer.email) : customer.email != null) return false; return company != null ? company.equals(customer.company) : customer.company == null; } @Override public int hashCode() { int result = name != null ? name.hashCode() : 0; result = 31 * result + (email != null ? email.hashCode() : 0); result = 31 * result + (company != null ? company.hashCode() : 0); return result; } @Override public String toString() { return "Customer{" + "name='" + name + '\'' + ", email='" + email + '\'' + ", company='" + company + '\'' + '}'; } }
data class Customer(var name: String, var email: String = "", var company: String = "")
var neverNull: String = "something" var mightBeNull: String? = null // "?" indicates this can be null if (neverNull.length > 0) { // This is OK … } if (mightBeNull.length > 0) { // Compiler catches this error for you … }
fun orderPizza(size: Size, pepperoni: Boolean, mushrooms: Boolean, ham: Boolean, pineapple: Boolean, pickles: Boolean, sausage: Boolean, peppers: Boolean, onion: Boolean) { ... } // Wait… did I just order pickles on my pizza? // Why do we even have that option? orderPizza(Size.LARGE, true, false, false, false, true, false, true, false)
fun orderPizza(size: Size, pepperoni: Boolean = false, mushrooms: Boolean = false, ham: Boolean = false, pineapple: Boolean = false, pickles: Boolean = false, sausage: Boolean = false, peppers: Boolean = false, onion: Boolean = false) { ... } orderPizza(Size.LARGE, ham = true, mushrooms = true)
// Please don't put this in your app! when { password.equals("password") -> println("Insecure password!") password.length < 4 -> println("Too short!") else -> { println("Secure password!") } }
if (obj is String) { // Compiler casts obj to a String for you. // (Would work with && instead of nested ifs too.) if (obj.length > 0) { … } }
// Assume reasonable implementations of Cat and Dog when (obj) { is Cat -> obj.meow(...) is Dog -> obj.woof(...) else -> { … } }
toPigLatin
// The "String." prefix indicates that this method should // extend the existing String class fun String.toPigLatin() : String { ... } val plainOldString : String = "some text" // Can now call toPigLatin as if were a method on String println(plainOldString.toPigLatin()) // Or: println("some text".toPigLatin())
data class Order(val itemCode: String, val quantity: Int, val price: Float)
fun getOrder(...): Order { ... return Order(itemCode, quantity, price); }
Order
what
howMany
howMuch
val (what, howMany, howMuch) = getOrder(...)
fun allStrings(collection: Collection)= collection.all { it is String }
fun generatePage(withEmphasis : Boolean) { val result = html { head { title { +"Kotlin Builders" } } body { h1 { +"Kotlin Builders" } p { +"This is " if (withEmphasis) b { +"really " } +"interesting" a(href = "https://goo.gl/rHwJio") { +"More here" } } } } println(result) }
html
head
body
withEmphasis
if (withEmphasis)
