I can write in java
int i = 10; String s = i==10 ? "Ten" : "Empty"; Even I can pass it in method parameter.
callSomeMethod(i==10 ? "Ten" : "Empty"); How do I convert it to kotlin? Lint shows error when writing same thing in kotlin.
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4 Answers
callSomeMethod( if (i==10) "Ten" else "Empty") Discussion about ternary operator: https://discuss.kotlinlang.org/t/ternary-operator/2116/3
2 Comments
Khemraj Sharma
Kotlin provide many shortcuts than Java, but now it fails.
Marko Topolnik
This is actually the standard syntax in FP languages, where flow-control constructs are expressions that can be evaluated. If you think Kotlin chases opportunities to provide "shortcuts" that replace four characters with one, no, that has never been Kotlin's goal.
Instead of
String s = i==10 ? "Ten" : "Empty"; Technically you can do
val s = if(i == 10) "Ten" else "Empty" val s = when { i == 10 -> "Ten" else -> "Empty" } val s = i.takeIf { it == 10 }?.let { "Ten" } ?: "Empty" // not really recommended, just writing code at this point val s = choose("Ten", "Empty") { i == 10 } inline fun <T> choose(valueIfTrue: T, valueIfFalse: T, predicate: () -> Boolean) = if(predicate()) valueIfTrue else valueIfFalse 
Comments
You can create an extension function with generic for boolean value
fun <T> Boolean.elvis( a :T, b :T ): T{ if(this) // this here refers to the boolean result return a else return b } and now you can use it for any boolean value (cool Kotlin)
// output System.out.print((9>6).elvis("foo","bar")) foo System.out.print((5>6).elvis("foo","bar")) bar 3 Comments
Khemraj Sharma
This is a nice answer. But I will use
if else way. Cause char counts are almost same, and I will not add extension to do same char count code.
Pavneet_Singh
@Khemraj thanks and thanks to you, I got the chance to play a little, I totally respect and agree with your decision , happy coding :)
Khemraj Sharma
By the way, thanks for sharing extension info. I am new to kotlin & appreciate your way.
As the original question was using the term 'Elvis operator' it may be a good idea to provide a short comparison with the ternary operator.
The main difference between ternary operator and Elvis operator is that ternary is used for a short if/else replacement while the Elvis operator is used for null safety, e.g.:
port = (config.port != null) ? config.port : 80;- a shortcut for an if/then/else statementport = config.port ?: 80- provides a default value to be used in case the original one isnull
The examples look very similar but the Ternary operator can be used with any type of boolean check while the Elvis operator is a shorthand for use config.port if it's not null else use 80 so it only checks for null.
Now, I think Kotlin doesn't have a ternary operator and you should use an if statement like so - s = if (i==10) "Ten" else "Empty"