1.继承与重写的Open关键字
Kotlin
open class Product(
val name:String
) {
fun description() = "Product: $name"
open fun load() = "Nothing .."
}
class LuxuryProduct:Product("Luxury"){//继承需要调用 父类的主构造函数
override fun load(): String {
return "LuxuryProduct loading ..."
}
}
fun main() {
val p:Product = LuxuryProduct()
println(p.load())
}2.类型检测
3.智能类型转化
Kotlin
import java.io.File
open class Product(
val name:String
) {
fun description() = "Product: $name"
open fun load() = "Nothing .."
}
class LuxuryProduct:Product("Luxury"){//继承需要调用 父类的主构造函数
override fun load(): String {
return "LuxuryProduct loading ..."
}
fun special():String = "Speical LuxuryProduct Function"
}
fun main() {
val p:Product = LuxuryProduct()
println(p.load())
println(p is Product)
println(p is LuxuryProduct)
println(p is File)
if (p is LuxuryProduct){
p.special()
}
}4. Any 超类
跨平台支持得更好，他的Any类里的 toString hashcode equals 在不同平台有不同的实现，是为了更好的跨平台支持。
5. 对象
5.1 object关键字 单例模式
Kotlin
object ApplicationConfig{
var name :String = "singleName"
init {
println("ApplicationConfig loading ...")
}
fun doSomething(){
println("doSomething")
}
}
fun main() {
//类名，实例名 就是一个单例对象
ApplicationConfig.doSomething()
println(ApplicationConfig)
println(ApplicationConfig)
println(ApplicationConfig)
println(ApplicationConfig===ApplicationConfig)
}
5.2 对象表达式 相当于匿名内部类
Kotlin
open class Player{
open fun load() = "loading nothing"
}
fun main() {
val p = object : Player(){ //匿名内部类相当于
override fun load(): String {
return "anonymous nothing"
}
}
println(p.load())
}5.3 伴生对象 一个类只能有一个
Kotlin
import java.io.File
open class ConfigMap(val name:String){
companion object{ //伴生对象 相当于静态内部类 创建的单例对象
// 不管这个ConfigMap类实例化多少次，这个伴生对象就是单例，因为是不基于对象创建的，是类加载时创建的
private const val PATH = "XXXX"
var s:String ="asd"
fun load() = File(PATH).readBytes()
}
}
fun main() {
ConfigMap.load()
}
Kotlin
import java.io.File
open class ConfigMap(val name:String){
companion object{ //伴生对象 相当于静态内部类 创建的单例对象
// 不管这个ConfigMap类实例化多少次，这个伴生对象就是单例，因为是不基于对象创建的，是类加载时创建的
private const val PATH = "XXXX"
var s:String ="asd"
fun load() = File(PATH).readBytes()
init {
println("companion object 被加载了")
}
}
}
fun main() {
ConfigMap("a")
}
6. 嵌套类 实际上就是 静态内部类
Kotlin
class Player2 {
class Equipment(var name: String) {
fun show() = println("equipment:$name")
}
fun battle(){
}
}
fun main() {
val equipment = Player2.Equipment("sharp knife")
}
7. 数据类
Kotlin
data class Coordinate(var x: Int, var y: Int) {
var isInBounds = x > 0 && y > 0
}
fun main() {
println(Coordinate(10, 20))
//== 比较的是内容，equals,Any 默认实现 === ,比较引用
//=== 比较引用
println(Coordinate(10, 20) == Coordinate(10, 20))
}8.copy函数 数据类专属
Kotlin
data class Student (var name:String,val age:Int){
private val hobby = "music"
var subject:String
init {
println("initializing student")
subject = "math"
}
constructor(_name:String):this(_name,10)
override fun toString(): String {
return "Student(name='$name', age=$age, hobby='$hobby', subject='$subject')"
}
constructor(_name:String,_age:Int,_hobby:String,_subject:String):this(_name,10){
subject=_subject
}
}
fun main() {
val s = Student("JACK")
val copy = s.copy(name = "Rose") //copy只跟主构造函数有关
println(s)
println(copy)
}9.结构声明
Kotlin
class PlayerScore(var experience:Int ,val level :Int,val name:String){
operator fun component1() = experience //component后面那个数字必须从1开始
operator fun component2() = name
}
fun main() {
/**
* 普通的结构
*/
val (x,y) = PlayerScore(10,20,"小智")
println("$x $y")
}
Kotlin
data class PlayerScore(var experience:Int ,val level :Int,val name:String){
}
fun main() {
/**
* 数据类自带的结构
*/
val (x,y) = PlayerScore(10,20,"小智")
println("$x $y")
}10. 运算符重载
Kotlin
data class Coordinate(var x: Int, var y: Int) {
var isInBounds = x > 0 && y > 0
// operator fun plus(other:Coordinate):Coordinate {
// return Coordinate(x+other.x,y+other.y)
// }
operator fun plus(other: Coordinate) = Coordinate(x+other.x,y+other.y)
}
fun main() {
val c1 = Coordinate(10, 20)
val c2 = Coordinate(10, 20)
println(c1+c2)
}11.枚举类
Kotlin
enum class Direction {
EAST,
WEST,
SOUTH,
NORTH
}
fun main() {
println(Direction.EAST)
println(Direction.EAST is Direction)
}11.1 枚举类定义函数
Kotlin
enum class Direction (private val coordinate: Coordinate){
EAST(Coordinate(1,0)),
WEST(Coordinate(-1,0)),
SOUTH(Coordinate(0,-1)),
NORTH(Coordinate(0,1));
fun updateCoordinate(playerCoordinate: Direction) =
Coordinate(playerCoordinate.coordinate.x+coordinate.x,
playerCoordinate.coordinate.y+coordinate.y)
}
fun main() {
val updateCoordinate = Direction.EAST.updateCoordinate(Direction.WEST)
println(updateCoordinate)
}11.2 代数数据类型
Kotlin
enum class LicenseStatus {
UNQUALIFIED,
LEARNING,
QUALIFIED;
}
class Driver(var status: LicenseStatus) {
fun checkLicense(): String {
return when (status) {
LicenseStatus.UNQUALIFIED -> "没资格"
LicenseStatus.LEARNING -> "在学"
LicenseStatus.QUALIFIED -> "有资格"
}
}
}
fun main() {
println(Driver(LicenseStatus.LEARNING).checkLicense())
}12.密封类
Kotlin
//密封
sealed class LicenseStatus2 {
object UnQualified : LicenseStatus2(){
val id :String = "2131"
}
object Learning : LicenseStatus2()
class Qualified(val licenseId: String) : LicenseStatus2()
}
class Driver2(var status: LicenseStatus2) {
fun checkLicense(): String {
return when (status) {
is LicenseStatus2.UnQualified -> "没资格 ${(this.status as LicenseStatus2.UnQualified).id}"
is LicenseStatus2.Learning -> "在学"
is LicenseStatus2.Qualified -> "有资格，驾驶证编号 ${(this.status as LicenseStatus2.Qualified).licenseId}"
}
}
}
fun main() {
println(Driver2(LicenseStatus2.UnQualified).checkLicense())
}