1. Data class: add the data keyword in front of the class
It will automatically generate equals(), hashCode(), toString() and other methods to reduce the amount of development code
data class Cellphone(val brand: String, val price: Double)
fun main(){
val cellphone = Cellphone("Xiaomi", 4999.0)
val cellphone2 = Cellphone("Huawei", 5999.0)
println(cellphone)
println(cellphone.hashCode())
println(cellphone.toString())
println("cellphone1 equals cellphone2: " + (cellphone == cellphone2))
}
2. Singleton class: object keyword
object Singleton {
fun singletonTest() {
println("singletonTest is called.")
}
}
transfer:
fun main(){
Singleton.singletonTest()
}
Kotlin automatically creates an instance of the Singleton class for us behind the scenes, and guarantees that there will only be one Singleton instance globally.