kotlin语言——接口，数据类，单例类

interface Study {//接口+interface
    fun readbooks()
    fun dohomework(){
        println("do homework default implementation")//在接口中加函数体的内容，代表着dohomework这个函数默认实现，
        //就是说在student继承哪里，可以不用override定义接口函数，不会报错，但readbook不行，因为没有加函数体
    }
}

class Student (name :String,age :Int):person(name,age),Study{//接口加继承的函数，person是类的继承，Study是接口
    override fun readbooks() {//override接口调用关键字，实现接口中的函数
        println(name+"is reading")
    }

    /*override fun dohomework() {
        println(name+"is doing homework.")
    }*/
}


/*fun main() {
    //val a =Student("123654",5,"nie",18)
    //val a=Student()
    //val a=Student("nie",18)
    val a=Student("niw",5)
     //a.name="nie"
     //a.age=18
     println(a.name+" is eating,he is "+a.age+" years old,他是 ")//+a.*grade+"年级的学生，学号是"+a.sno)
}*/

fun main(){
    val student=Student("jack",19)
    //doStudy(student)
    student.readbooks()
    student.dohomework()
}
/*fun doStudy(study: Study){
    study.readbooks()
    study.dohomework()
}*/

package com.example.myapplicationone

   data class Cellphone (val brand:String,val price:Double)//定义数据类方法，关键字data,kotlin强大的推理能力，
                                                          // 只需要data关键字就可以实现数据类的定义，
                                                            //不需要其他的equals,hashcode,tostring

fun main(){
    val cellphone1=Cellphone("samsung",1299.33)
    val cellphone2=Cellphone("samsung",1299.33)
    println(cellphone1)
    println("cellphone1=cellphone2  " +(cellphone1==cellphone2))
}

package com.example.myapplicationone

object Singleton {//单例类关键字“object“
    fun singletonTest(){
        println("singletonTest is called")
    }
}

fun main(){
    Singleton.singletonTest()//单例类调用方法
}