Kotlin 基本语法5 继承，接口，枚举，密封-编程知识

1.继承与重写的Open关键字

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

import java.io.Fileopen 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

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

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

import java.io.Fileopen 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()
}

import java.io.Fileopen 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

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

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

data class Student (var name:String,val age:Int){private val hobby = "music"var subject:Stringinit {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

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")}

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

 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

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

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

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

//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())
}