A discussion about Kotlin, including migration from Java project to Kotlin.

https://kotlinlang.org/docs/reference/comparison-to-java.html
All the pros and almost non of the cons.

Kotlin fixes a series of issues that Java suffers from:

Null references are controlled by the type system.
No raw types
Arrays in Kotlin are invariant
Kotlin has proper function types, as opposed to Java's SAM-conversions
Use-site variance without wildcards
Kotlin does not have checked exceptions

What Kotlin has that Java does not

Lambda expressions + Inline functions = performant custom control structures
Extension functions
Null-safety
Smart casts
String templates
Properties
Primary constructors
First-class delegation
Type inference for variable and property types
Singletons
Declaration-site variance & Type projections
Range expressions
Operator overloading
Companion objects
Data classes
Separate interfaces for read-only and mutable collections
Coroutines