Kotlin接口实现

 面向接口编程 = 多态

open class Person(val name: String, val age: Int) {
    fun think() {
        println("Mr./Ms.$name, who is $age years old, is thinking!")
    }
}

interface Study {
    fun preview()
    fun takeNotes()
    fun review()
/*  fun takeNotes() {
        println("This's the function of taking notes.")
    }

解释：如果接口中的一个函数拥有函数体，那这个函数体就是其默认实现，
当一个类去实现Study接口时，便只会强制要求实现preview和review函数*/
}

class Student(name: String, age: Int) : Person(name, age), Study {
    override fun preview() {
        println("Mr./Ms.$name is previewing.")
    }
    override fun takeNotes() {
        println("Mr./Ms.$name is taking notes.")
    }
    override fun review() {
        println("Mr./Ms.$name is reviewing.")
    }
}

fun main () {
    val student = Student("Jack", 19)
    student.preview()
    student.takeNotes()
    student.review()
    student.think()
}