fun String.last() : Char {
return this[length - 1] // Using built-in extension for array indexing!
}
val x
= "Hey!"
println(x.last()) // Prints "!".
Half of Guava* and 2/3rds of the Cash app* is comprised of static utility methods. While this
wouldn't eliminate their presence, it would allow you to use them directly on the types for which
they were implemented. This is a big win for readability. Death to the plurals (Collections), the
numbereds (Collections2), and the 'util' suffixeds (StringUtils).
* Not even remotely a true statistic
(See the Kotlin documentation for more.)
DataClasses
Akin to what value types in Java 10 are hoping to accomplish, data classes are those which
exist only to group data in a semantic, immutable type. We currently use AutoValue to simulate
value types in an easy fashion.
data class Money(val currency: String, val amount: Int)
This class gives you equals, hashCode, toString for free. Each component is exposed by a
read-only property of the same name. There is also a copy method for changing values into a
new instance.
val money = Money("USD", 100)
val moreMoney = money.copy(amount = 200) // Oh hey named params!
Instances can be unpacked with multi-assignment. This is similar to Python's tuples and has
been shimmed into the standard library such as for Map.Entry when looping over a map.
for ((key, value) in map) {
println(key + ": " + value)
}
(See the Kotlin documentation for more.)
OtherAwesomeThings
● Classes and methods are final by default. You can declare them open if you want
extensibility.
