** * An iterator over a collection that supports indexed access. each loop: for (i in 1.5) print(i) // Prints: 1234 for (i in 'b'. ListIterator also has nextIndex and previousIndex functions which return the index of the elements. The Int, Long, and Char type ranges can be used to iterate over next values in the for. It has hasPrevious and previous functions which can be used to traverse in the backward direction.

We are shutting down our process and we need to interrupt our run.In order to iterate over a list, we have another Iterator ie ListIterator which provides the additional functionality of traversing to the previous element also.

Now comes the twist: We have to be able to stop mid-way. This is just an example taken to the absolute extreme for the sake of discussion.Īs far as performance, all implementations will take ~50 seconds to run (100 x 500ms). I recommend watching Putting Down the Golden Hammer from KotlinConf 2019 for an interesting discussion on that. From 6 lines of code we are down to 1.Īs a side-note, implicit return types and putting everything in one line are not necessarily Best Practice. We’ve even removed the explicit return type for brevity. Our boilerplate will look like this: class Iterations

Let’s take an example of a loop that receives a list of customer IDs and sends them an email.

Assuming you also want to collect results as you iterate, you can run the gamut with syntax styles ranging from the very Java-esque to super streamlined functional code. There are many ways to iterate over collections in Kotlin. It is a summary of a discussion we had over a PR in which we wanted to terminate an execution loop over a collection. This post follows and discusses different Kotlin code styles we can use for stopping a long running task.

Kotlin for each example