Kotlin’s List from the standard library is readonly: interface List<out E> : Collection<E> (source) A generic ordered collection of elements. Methods in this interface support only read-only access to the list; read/write access is supported through the MutableList interface. Parameters E – the type of elements contained in the list. As mentioned, there is also … Read more
They’re called platform types and they mean that Kotlin doesn’t know whether that value can or cannot be null and it’s up to you to decide if it’s nullable or not. In a nutshell, the problem is that any reference coming from Java may be null, and Kotlin, being null-safe by design, forced the user … Read more
It is true that there appears to be little existing documentation for the concept of receivers (only a small side note related to extension functions), which is surprising given: their existence springing out of extension functions; their role in building a DSL using said extension functions; the existence of a standard library function with, which … Read more
In Kotlin, if statements are expressions. So the following code is equivalent: if (a) b else c The distinction between expression and statement is important here. In Java/C#/JavaScript, if forms a statement, meaning that it does not resolve to a value. More concretely, you can’t assign it to a variable. // Valid Kotlin, but invalid … Read more
In your code result is not changing, its var properties are changing. Refer comments below: fun copyAddress(address: Address): Address { val result = Address() // result is read only result.name = address.name // but not their properties. result.street = address.street // … return result } val is same as the final modifier in java. As … Read more
Between execution of left != null and queue.add(left) another thread could have changed the value of left to null. To work around this you have several options. Here are some: Use a local variable with smart cast: val node = left if (node != null) { queue.add(node) } Use a safe call such as one … Read more
It’s really not much different from how you’d do it in Java since Kotlin uses Java’s frameworks/libraries and its JVM. Just apply the necessary Kotlin plugins and configurations in Android Studio, convert the Java code to Kotlin, and then refer to the Kotlin docs for potential bug fixes and whatnot.