Is there even a simpler way to express anonymous classes in Kotlin?

Question

I translated this Java

new Thread("Cute Thread") {
  public void run() {
    int a = 3;
  }
}.start();

to this Kotlin

object : Thread("Cute Thread") {
  override fun run() {
     val a = 3
  }
}.start()

But I feel that there is a simpler way of doing this, however I can't find any examples.

I've tried

  Thread("Cute Thread") { val a = 3 }.start()

But with no success...

PS. I know that starting a Thread like this is a bad practice.

Answer 1

There's no different way to implement an anonymous class (except SAM conversions).
But you can still simplify your code by:

 Thread({ val a = 3 }).start()

or with thread name:

Thread({ val a = 3 }, "Cute Thread").start()

Answer 2

One issue here is that the Thread class constructor has parameters in a bad order for Kotlin. For Runnable you can easily use a SAM conversion (a single method interface can be treated as a lambda) but because the lambda is not the last parameter it looks kinda clunky. In the case where there is only one parameter it is fine:

Thread { val a = 3 }.start()

However with more than one parameter, they are backwards causing this uglier syntax with the lambda as a parameter inside the parenthesis:

Thread({ val a = 3 }, "some name").start()

Instead you should use the Kotlin stdlib function thread()

With that function you have simpler syntax of:

// create thread, auto start it, runs lambda in thread
thread { val a = 3 }  

// create thread with given name, auto start it, runs lambda in thread
thread(name = "Cute Thread") { val a = 3 }  

// creates thread that is paused, with a lambda to run later
thread(false) { val a = 3 } 

// creates thread that is paused with a given name, with a lambda to run later
thread(false, name = "Cute Thread") { val a = 3 } 

See also: thread() function documentation