1、Kotlin中的数据类主要用于保存数据。对于每个数据类，编译器会自动生成其他成员函数，允许您将实例打印到可读输出、比较实例、复制实例等。
中文文档：
https://book.kotlincn.net/text/data-classes.html
2、新建文件dataClassTest.kt
3、代码
data class User1(val name: String, val age: Int)fun main(args: Array<String>) {val jack = User1(name = "Jack", age = 1)val olderJack = jack.copy(age = 2)println(jack)println(olderJack)val jane = User1("Jane", 35)val (name, age) = janeprintln("$name, $age years of age") // prints "Jane, 35 years of age"
}4、kotlin的数据类，声明简单方便，还可以在类体中声明属性：
data class Person(val name: String) {var age: Int = 0
}
fun main() {val person1 = Person("John")val person2 = Person("John")person1.age = 10person2.age = 20println("person1 == person2: ${person1 == person2}")// person1 == person2: trueprintln("person1 with age ${person1.age}: ${person1}")// person1 with age 10: Person(name=John)println("person2 with age ${person2.age}: ${person2}")// person2 with age 20: Person(name=John)
}5、类体中声明属性的输出：
6、复制
fun main(args: Array<String>) {val jack = UserCopy(name = "Jack", age = 1)val olderJack = jack.copy(age = 2)println(olderJack)
}7、复制的输出
