Security
Kotlin is more secure than Java, mainly due to two language features
Null safety
The following code is not possible:
Variables in Kotlin are not nullable unless explicitely stated. How do we prevent a compilation error in the above piece of code?
Solution
Add a "?" to the value type to allow this:
But if you want to do something with those nullable values, you have to check for null:
(Using the ?. operator. This is the "null safe dot operator", or "safe call operator").
==> Before running the snippet further down: what do you think is displayed?
See https://kotlinlang.org/docs/reference/null-safety.html for more examples. If you are familier with freemarker you might recognise similarites: https://freemarker.apache.org/docs/dgui_template_exp.html#dgui_template_exp_missing
Emphasis on Immutabilty
Shared mutable state is the root of all evil
Kotlin has one main constructs to prevent shared mutable state:
val vs var keyword
This code fails, because it reassigns to a val, you would have to change above code to a var.
This also works with java, using the "final" keyword
But there are some issues with the final keyword, mainly that it is ambigous: it is both used to declare variables immutable and to put constraints on inheritance. Furthermore you always have to ask yourself if you really want to use a var in Kotlin, while in Java you have to not forget the final keyword
