How to initialize a Thread in Kotlin?

Question

In Java it works by accepting an object which implements runnable :

Thread myThread = new Thread(new myRunnable()) 

where myRunnable is a class implementing Runnable.

But when I tried this in Kotlin, it doesn't seems to work:

var myThread:Thread = myRunnable:Runnable 

Answer 1

Kotlin comes with a standard library function thread, which I'd recommend to use here:

public fun thread(     start: Boolean = true,      isDaemon: Boolean = false,      contextClassLoader: ClassLoader? = null,      name: String? = null,      priority: Int = -1,      block: () -> Unit): Thread 

You can use it like this:

thread {     Thread.sleep(1000)     println("test") } 

It has many optional parameters for e.g. not starting the thread directly by setting start to false.

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Alternatives

To initialize an instance of class Thread, invoke its constructor:

val t = Thread() 

You may also pass an optional Runnable as a lambda (SAM Conversion) as follows:

Thread {     Thread.sleep(1000)     println("test") } 

The more explicit version would be passing an anonymous implementation of Runnable like this:

Thread(Runnable {     Thread.sleep(1000)     println("test") }) 

Note that the previously shown examples do only create an instance of a Thread but don't actually start it. In order to achieve that, you need to invoke start() explicitly.

Answer 2

Runnable:

val myRunnable = runnable {  } 

Thread:

Thread({   // call runnable here   println("running from lambda: ${Thread.currentThread()}") }).start() 

You don't see a Runnable here: in Kotlin it can easily be replaced with a lambda expression. Is there a better way? Sure! Here's how you can instantiate and start a thread Kotlin-style:

thread(start = true) {         println("running from thread(): ${Thread.currentThread()}")     }