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) = jane
    println("$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 = 10
    person2.age = 20

    println("person1 == person2: ${person1 == person2}")
    // person1 == person2: true

    println("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