Data classes offer a quick and easy way to make a class which stores data. If you want to do this in java you need to override the following methods:
toString()
equals()
hashCode()
In Kotlin however, these are auto-generated from the properties in the primary constructor. Values not in the primary constructor are not referenced in these methods so would require you create your own implementation.

                        
        data class BlogPost(val title: String,
                            val author: String)
    
            fun main() {
            val kotlinDataClasses =  BlogPost("Kotlin: Data Class", "Hoinzey")
    
            println("Thank you for reading \"${kotlinDataClasses.title}\"")
            //Thank you for reading "Kotlin: Data Class"
        }
                    

Requirements for data classes

* The primary constructor needs to have at least one paramater
* All paramaters need to be either val or var
* They can't be abstract, open or inner

Useful stuff

It is generally recommended that your data classes should be immutable. To make it easier to work with immutable objects Kotlin generates the copy() method which allows us to copy/clone the object and change some of its properties

                        
    val nextBlogPost = kotlinDataClasses.copy(title = "RecyclerView", rating = "2/5")
                    

If you don't want something to be used in the auto-generated methods then you can declare it inside the body of the class

                        
    data class BlogPost(val title: String,) {
        val author = "Hoinzey"
    }