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Todd Ginsberg

Kotlin for 4 years Java for 20 years

Netspend - Payment company in Austin

Kotlin - Satically typed language developed by JetBrains. Released under Apache 2 License.

designed as a General Purpose language

Targets multple backends - Java 6 or 8, JavaScript, Native platforms due to LLVM

100% interoperable with Java

Designed to avoid Defects (Null Pointer Exceptions, etc.)

Lots of small improvements that add up

More compact, lots of good syntactic sugar reduces cognitive load

189,000 Null-safety issues on Github.

"WHat is a null pointer exception" shows up 15,000 times on Stack Overflow

Kotlin steals good features from other languages - Groovy, Python, etc.

Good Community

Spring Framework 5.0 has Kotlin support, 5.2 is better.

  • Nullability works right.
  • Really good examples in Kotlin in the docs

Roman Elizarov - JetBrains

The most common case is the default. Less boilerplate means less cogniitive load.

val vs var - Invariants are first class citizens.

Kotlin - Semicolons are optional

String interpolation: "foo $bar"

Type inference makes types optional most of the time.

Kotlin has syntactic sugar for "=="

Ref equality is "===" as in Javascript

Triple quotes for strings, just like python

Null Safety.

Traversal operator:

var foo : String? = "Austin"
foo?.toUpperCase()

Kotlin override:

val lowest: Int? = listOf(1,2,3).min()!!

When - "Case" on steroids.

When allows smart casting:

when (x) {
  is Int -> print x % 2 == 0)
  is String -> print( x.length +1) 
  is
}

Don't need to specify implement or extends, just use ":"

Oope can be extend, otherwise it can't.

Kotlin has no "new" keyword

Autogenerated setters and getters. Auto-calling getters and setters

Kotlin has data classes (includes toString, hashCode and equals) Data classes include copy constructors

Spring Boot 2.2 allows data classess as @ConfiguraitonProperties

Kotlin allows defaultable parameters.

Kotlin allows named parameters to be called in different orders.

  • Be careful because parameter names are now part of the API spec

Kotlin allows you to "push" functions into objects:

fun Int.isEven() : boolean {
  return it % 2  == 0 
}

Apply is awesome:

  val p = Person().apply {
    name="Todd",
    age=21
  }

functions are final by default, unless you open them. arguments are always final functions can be defined outside of a class (like static functions, kind of) Kotlin supports tail recursive functions

Checked excepitons aren't mandatory, they're all Runtime, just deal with it.