In this post on Kotlin\u2019s data classes, we\u2019ll take a look at how data classes are better than regular Java POJO (Plain Old Java Object) classes, and how they make our everyday lives easier. We\u2019ll also take a look at some of the caveats of data classes.<\/p>\n
I\u2019ve also written an article on Java vs Kotlin<\/strong>, if you\u2019re interested, check it out here:<\/p>\n Have a look at this Java class:<\/p>\n All of this ceremony for a simple Java POJO class used to hold some data. You might have used such classes when serializing\/deserializing a JSON response from an API. It provides you getters and setters for the properties. Now let\u2019s see how it\u2019s done in Kotlin with the help of data classes:<\/p>\n Just a single line! We can go ahead and use this class in the same way as the java class. Getters and setters are compiler generated for us.<\/p>\n Even the methods such as toString(), hashCode() and equals() are compiler generated.<\/strong> Also, methods such as componentN and copy are generated but they have a caveat. We\u2019ll talk about them in upcoming sections.<\/p>\n Data classes<\/strong> are final<\/strong> by default. They cannot be abstract, open, sealed or inner<\/strong>. They can only inherit from other non-data classes (eg. sealed classes after 1.1, before 1.1 data classes can only implement interfaces).<\/p>\n Data classes can override properties and methods from the interfaces they implement.<\/p>\n We know that hashCode, toString and equals<\/strong> are auto generated for data class. But we can explicitly provide our own implementations of these in data class body. In such case, the explicit implementations are used.<\/strong><\/p>\n <\/strong>We cannot provide explicit implementations of componentN() and copy() functions.<\/strong><\/p>\n\n
Boilerplate!<\/h2>\n
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\n \n \n class<\/code> Dog{<\/code><\/div>\n <\/code>private<\/code> String name;<\/code><\/div>\n <\/code>private<\/code> String sound;<\/code><\/div>\n <\/code>private<\/code> String age;<\/code><\/div>\n <\/code>public<\/code> String getName() {<\/code><\/div>\n <\/code>return<\/code> name;<\/code><\/div>\n <\/code>}<\/code><\/div>\n <\/code>public<\/code> void<\/code> setName(String name) {<\/code><\/div>\n <\/code>this<\/code>.name = name;<\/code><\/div>\n <\/code>}<\/code><\/div>\n <\/code>public<\/code> String getSound() {<\/code><\/div>\n <\/code>return<\/code> sound;<\/code><\/div>\n <\/code>}<\/code><\/div>\n <\/code>public<\/code> void<\/code> setSound(String sound) {<\/code><\/div>\n <\/code>this<\/code>.sound = sound;<\/code><\/div>\n <\/code>}<\/code><\/div>\n <\/code>public<\/code> String getAge() {<\/code><\/div>\n <\/code>return<\/code> age;<\/code><\/div>\n <\/code>}<\/code><\/div>\n <\/code>public<\/code> void<\/code> setAge(String age) {<\/code><\/div>\n <\/code>this<\/code>.age = age;<\/code><\/div>\n <\/code>}<\/code><\/div>\n}<\/code><\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n\n\n
\n \n \n data <\/code>class<\/code> Dog(var name: String, var age: String, var sound: String)<\/code><\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\nInheritance in Data Classes<\/b> <\/strong><\/h2>\n
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\n \n \n interface<\/code> Animal{<\/code><\/div>\n <\/code>val name:String<\/code><\/div>\n <\/code>fun sound()<\/code><\/div>\n}<\/code><\/div>\ndata <\/code>class<\/code> Dog(override val name:String):Animal{<\/code><\/div>\n <\/code>override fun sound(){<\/code><\/div>\n <\/code>println(<\/code>\"Barks\"<\/code>)<\/code><\/div>\n <\/code>}<\/code><\/div>\n}<\/code><\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\nComponentN() functions in data classes<\/b><\/h2>\n