Kotlin introductory notes (VI) interface and function visibility modifiers

Preface : This tutorial is best done with JAVA Study on the basis of

One 、 Interface

Kotlin Interface and Java Almost exactly the same

Define an interface ：

interface Study{
    fun readBooks()
    fun doHomework()
}

use Student Implement this interface ：

class Student(name : String , age : Int) :  Study {
    override fun readBooks() {
        println(name + " is reading.")
    }
    override fun doHomework(){
        println(name + " is doing homework.")
    }
}

be familiar with Java The person must specify ,Java For inheritance of extends  , The interface is implemented with implements  , and Kotlin Unified use :  （ The colon ）.

Now we can main() Function, write the following code to call the functions in these two interfaces

fun main() {
    val student = Student("Jack",19)
    doStudy(student)
}
fun doStudy(study : Study) {
    study.readBooks()
    study.doHomework()
}

however Kotlin Also added a function ：

        Allows default implementation of functions defined in the interface .

Don't talk much , Code up ：

interface Study {
    fun readBooks()
    fun doHomework() {
        println("do homework default implementation.")
    }
}

  At this time, you will find ,Student Will only force the implementation of readBooks A function .

Two 、 Visibility modifier of function

Default modifier ：

               Java :  default

               Kotlin : public

Kotlin Abandoned Java Medium default , Introduced a new concept ：internal , Indicates that it is only visible to classes of the same module . protected stay Java And Kotlin It's different , See the following table for details ：

Java And Kotlin Function visibility modifier comparison table

Modifier	Java	Kotlin
public	All classes are visible	All classes are visible （ Default ）
private	The current class is visible	The current class is visible
protected	The current class 、 Subclass 、 Classes under the same package path are visible	The current class 、 Subclasses are visible
default	Classes under the same package path are visible （ Default ）	nothing
internal	nothing	Class visible in the first mock exam module

If you like this series , You might as well pay attention ！ Thank you for watching ！

Reference resources :

        《 First line of code Android ( The third edition )》   --- Guo Lin