What are the advantages of Kotlin over Java?

Basically for me less thinking required to write kotlin equivalent to most java code:

data class

• java: you have to write getters and setters for each thing, you have to write hashCode properly (or let IDE auto generate, which you have to do again every time you change the class), toString (same problem as hashcode) and equals (same problem as hashCode). or you could use lombok, but that comes with some quirky problems of its own. record types are hopefully on the way. *kotlin: data class does it all for you.

getter and setter patterns

• java: rewrite the getter and setter for each variable you use it for
• kotlin: don’t have to write getter and setter, and custom getter and setter take a lot less typing in kotlin if you do want to. also delegates exist for identical getters\setters

abstract vs open classes

• java: you have to make an abstract class implementation
• kotlin: open class lets you make an inheritable class while also being usable itself. nice mix of interface and regular class imo

extension functions

• java: doesnt exist
• kotlin: does exist, makes functions more clear in usage and feels more natural.

null

• java: Anything but primitives can be null at any time.
• kotlin: you get to decide what can and cant be null. allows for nice things like inline class

singleton

• java: Memorize singleton pattern
• kotlin: object instead of class

generics

• java: Theyre alright, nothing fancy
• kotlin: Reified generics (you can access the actual type), in and out for covariance

named parameters

• java: does not exist, easy to break api back-compatibility if you arent careful.
• kotlin: does exist, easy to preserve api back-compatiblity.

primary constructor

• java: does not have per-se, you still have to define everything inside the class
• kotlin: very nice to be able to quickly write a constructor without any constructor function or extra needless declarations