Kotlin basic learning 13

Catalog

1.Kotlin The default implementation of the interface of the language

2.Kotlin Abstract class learning of language 、

3.Kotlin Language defined generic classes

4.Kotlin Language definition generic function learning

5.Kotlin Language definition generic transformation practice

6.Kotlin Language definition generic type constraint learning

7.Kotlin Defined by language vararg keyword ( Dynamic parameters )

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1.Kotlin The default implementation of the interface of the language

interface IUSB2{
    // 1. Interface var  You cannot assign values to the members of the interface ( But there are other ways )
    // 2. Any class   Interface    wait  val Represents read-only , Is it possible to assign values dynamically later （ There is no other way ）
    val usbVersionInfo:String //USB Version related information 
        get() = (1..100).shuffled().last().toString()
        // val  Unwanted set
    val usbInsertDevice:String //USB Inserted device information 
        get() = " Advanced device access USB"
        // val Unwanted set
    fun insertUSB() : String
}
// mouse USB Implementation class 
class Mouse2 : IUSB2 {
    override val usbVersionInfo: String
        get() = super.usbVersionInfo
    override val usbInsertDevice: String
        get() = super.usbInsertDevice
    override fun insertUSB() = "Mouse $usbVersionInfo, $usbInsertDevice"

}

// TODO 101.Kotlin  The default implementation of the interface of the language 
// 1. Be careful ： It's not right to do so , Because interface members are originally used to declare Standards 
//          But it can be done when the interface member is declared , Complete the implementation of interface members 
fun main(){
//    val iusb1 : Mouse2()
//    println(iusb1.insertUSB())
}

2.Kotlin Abstract class learning of language 、

abstract class BaseActivity{
    fun onCreate(){
        setContentView(getLayoutID())
        initView()
        initData()
        initXXX()
    }
    private fun setContentView(layoutID:Int) = println(" load ${layoutID} Layout xml in ")
    abstract fun initView()
    abstract fun initData()
    abstract fun initXXX()
    abstract fun getLayoutID() : Int
}
class MainActivity : BaseActivity(){
    override fun initView() {
        println(" Do specific initialization View The implementation of the ")
    }

    override fun initData() {
        println(" Implement specific initialization data ")
    }

    override fun initXXX() {
        println(" Do specific initialization XXX The implementation of the ")
    }

    override fun getLayoutID(): Int = 546
    fun show(){
        super.onCreate()
    }
}

// TODO 101.Kotlin  Abstract class learning of language 
fun main() = MainActivity().show()

3.Kotlin Language defined generic classes

class KtBase102<T>(private val obj : T){// Universal output 
    fun show () = println(" Universal output ：$obj")
}
data class Student(val name :String , val age : Int,val sex : Char)
data class Teacher(val name :String , val age : Int,val sex : Char)

// TODO 102.Kotlin  Language defined generic classes 
fun main(){
    val stu1 = Student(" Zhang San ",66,' male ')
    val stu2 = Student(" Li Si ",56,' male ')
    val tea1 = Teacher(" Wang Wu ",46,' male ')
    val tea2 = Teacher(" Zhao Liu ",36,' male ')

    KtBase102(stu1).show()
    KtBase102(stu2).show()
    KtBase102(tea1).show()
    KtBase102(tea2).show()

    KtBase102(String(" Liu er ".toByteArray())).show()

    KtBase102(456).show()
    KtBase102(456.23).show()
    KtBase102(456.3f).show()
    KtBase102(' male ').show()
}

4.Kotlin Language definition generic function learning

// 1. Universal object returner  Boolean  To control whether to return   Application takeif
class KtBase103<T>(private val isR : Boolean, private val obj : T){// Universal output 
    fun getObj() : T? = obj.takeIf { isR }
}
// TODO 103.Kotlin  Language definition generic function learning 
fun main(){
    val stu1 = Student(" Zhang San ",66,' male ')
    val stu2 = Student(" Li Si ",56,' male ')
    val tea1 = Teacher(" Wang Wu ",46,' male ')
    val tea2 = Teacher(" Zhao Liu ",36,' male ')

    //2. Four objects print 
    println(KtBase103(true,stu1).getObj())
    println(KtBase103(true,stu2).getObj())
    println(KtBase103(true,tea1).getObj())
    println(KtBase103(true,tea2).getObj())
    println(KtBase103(false,tea2).getObj() ?: " Your universal returner , Is to return null")
    println()
    //3. Object printing  + run +? :
    val r :Any  = KtBase103(true,stu1).getObj()?.run {
        // If getObj  Return value   Will come in 
        //this == getobj In itself 
        println(" The return object is ：$this")
        456.5f
    } ?: println(" The universal returner returns null")
    println(r)
    println()
    //4. Object printing  + apply + ?:
    val r3 : Teacher  = KtBase103(true,tea1).getObj().apply {
        if(this == null){
            println(" Universal output returns null")
        } else{
            println(" The universal output object is ：$this")
        }
    }!!
    println("r3:$r3")
    println()
    show("Bxb")
    show("Wuwu")

}
//5.show(t:T) + also + ?:
fun <B> show(item:B){
    item ?.also {
        println(" The universal object is ：$it")
    } ?: println(" eldest brother , Your universal object returner returns null")
}

5.Kotlin Language definition generic transformation practice

package com.bxb.s6
// 1. class  isMap map takeif map  What type is it 
class KtBase105<T>(val isMap:Boolean = false,val inputType :T){
    inline fun <R> map(mapAction : (T) -> R) = mapAction(inputType).takeIf { isMap }
}
inline fun <I,O> map(inputValue: I,isMap: Boolean = true,mapActionLambda:(I) -> O)=
    if(isMap) mapActionLambda(inputValue) else null
// TODO 104.Kotlin  Language definition generic transformation practice 
fun main(){
    //2.map int -> str What type of 
    val p1 = KtBase105(isMap = false,inputType = 4563)
    val r = p1.map {
        it
        it.toString()
        " my it yes $it"
    }
    //4. Verify whether it is this type   and  null
    val str1 : String = "OK1"
    val str2 : String? = "OK2"
    println(r is String)
    println(r is String?)
    println()
    //3.map per -> stu  What type of final reception 
    val p2 = KtBase105(true,Persons(" Li Si ",88))
    val r2 : Students? = p2.map {
        it
        Students(it.name,it.age)
    }
    println(r2)
    println()
    //map function   imitation RxJava Change operation 
    val r3 = map(123){
        it.toString()
        "map The parcel [$it]"
    }
    println(r3)
}
data class Persons(val name:String,val age : Int)
data class Students(val name:String,val age: Int)

6.Kotlin Language definition generic type constraint learning

package com.bxb.s6
open class MyAntClass(name : String) // Ancestry   Top level parent class 
open class PersonClass(name :String) : MyAntClass(name = name ) //  Parent class 
class StudentClass(name :String) : PersonClass(name = name ) //  Subclass 
class TeacherClass(name :String) : PersonClass(name = name ) //  Subclass 
class DogClass(name : String) // Other categories   alternative 
class CatClass(name : String)
// TODO 105.Kotlin  Language definition generic type constraint learning 
class KtBase106<T : PersonClass>(private val inputTypeValue:T,private val isR : Boolean = true){
    // Universal object returner 
    fun getObj() = inputTypeValue.takeIf { isR }
}
fun main(){
    val any = MyAntClass("Bxb1")
    val per = PersonClass("Bxb1")
    val stu = StudentClass("Bxb1")
    val tea = TeacherClass("Bxb1")
    val dog = DogClass("Wang1")
    val r2 = KtBase106(per).getObj()
    println(r2)
    val r3 = KtBase106(stu).getObj()
    println(r3)
    val r4 = KtBase106(tea).getObj()
    println(r4)
}

7.Kotlin Defined by language vararg keyword ( Dynamic parameters )

package com.bxb.s6
class KtBase107<T>(vararg objects : T,var isMap : Boolean){
    //1.objectArray:Array<T>
    //out  our T Can only be   Read , Do not modify 
    private val objectArray : Array<out T> = objects
    fun showObj(index : Int) : T? = objectArray[index].takeIf { isMap } ?: null
    fun <O> mapObj(index: Int,mapAction : (T ?) -> O) = mapAction(objectArray[index].takeIf { isMap })
}
// TODO 107.Kotlin  Defined by language vararg keyword ( Dynamic parameters )
fun main(){
    val p:KtBase107<Any?> = KtBase107("Bxb",false,4585,4526.3f,456.32,null,'C',isMap = true)
    println(p.showObj(0))
    println(p.showObj(1))
    println(p.showObj(2))
    println(p.showObj(3))
    println(p.showObj(4))
    println(p.showObj(5))
    println(p.showObj(6))
    println()
    val r: Int = p.mapObj(0){
        it
        it.toString()
        it.toString().length
    }
    println(" The string length of the zeroth element is ：$r")

    val r2 : String = p.mapObj(2){
        " My third element is :$it"
    }
    println(r2)
    val p2:KtBase107<String> = KtBase107("AAA","BBB","CCC",isMap = true)
    val r3 = p2.mapObj(2){
        it
        " I want to turn you into String type  it:$it"
    }
    println(r3)
}