CODEWITHSUNDEEP
kotlininstanceof
matteo
matteo

Reputation: 2401

Get type of a variable in Kotlin

How can I find the variable type in Kotlin? In Java there is instanceof, but in Kotlin it does not exist:

val properties = System.getProperties() // Which type?

Upvotes: 82

Views: 108150

Answers (5)

Willi Mentzel
Willi Mentzel

Reputation: 29844

You can do it like this:

val number = 5

// Get type of variable
println(number::class.simpleName)    // "Int"
println(number::class.qualifiedName) // "kotlin.Int"

// Check for specific type
if(number is Int) {
   println("number is of type Int")
}

You can also get the type of a class as String using reflection:

println(Int::class.simpleName)    // "Int"
println(Int::class.qualifiedName) // "kotlin.Int"

Please note:

On the Java platform, the runtime component required for using the reflection features is distributed as a separate JAR file (kotlin-reflect.jar). This is done to reduce the required size of the runtime library for applications that do not use reflection features. If you do use reflection, please make sure that the .jar file is added to the classpath of your project. (Source)

Upvotes: 123

richardun
richardun

Reputation: 713

If you want the class type in Kotlin (as opposed to Java):

val value="value"
println(value::class)

Upvotes: 1

user20632334
user20632334

Reputation:

Just a minor detail between mentioned answers.

var x = "X"
println(x::class.simpleName) // prints String

This code uses Reflection under the hood when you decompile it to Java bytecode and it looks like this Reflection.getOrCreateKotlinClass(x.getClass()).getSimpleName()

var y = "Y"
println(y.javaClass.simpleName) // prints String

And this would compile down to y.getClass().getSimpleName() and it's about 50 milliseconds faster.

Upvotes: 3

Jawad Fadel
Jawad Fadel

Reputation: 820

You can use like this:

val value="value"
println(value::class.java.typeName)

Upvotes: 39

Ivan Yulin
Ivan Yulin

Reputation: 1046

you can get the class name with properties::class.simpleName

Upvotes: 5

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