Our build tool of choice is Gradle, so the dependency on the kotlinx-coroutines-core library will look like this: So we need to add the dependency to the kotlinx-coroutines-core library before starting to write coroutines: The Kotlin language gives us basic constructs for writing coroutines but more useful constructs built on top of the basic coroutines are available in the kotlinx-coroutines-core library. We will change this program to run using coroutines in the next sections. However, the program ends with exit code 0 only after the longRunningTask finishes executing on Thread-0. It executes the longRunningTask() on thread Thread-0 but does not wait for it to complete and proceeds to execute the next println() statement again on the thread: main. : Thread-0Īs we can see in the output, the program starts running on the thread: main. Let us start by running a program that will execute some statements and also call a long-running function:Įxecuting longRunningTask on.: Thread-0 This article is accompanied by a working code example on GitHub. In this post, we will understand how to use coroutines in Kotlin. This way we can run many coroutines concurrently using only a small pool of threads thereby using very limited system resources.

When a coroutine is suspended, the corresponding computation is paused, removed from the thread, and stored in memory leaving the thread free to execute other activities. We can further resume the coroutine to run on the same or a different thread. We can suspend a coroutine to allow other coroutines to run on the same thread. They are computations that run on top of threads. Threads are an expensive resource and too many threads lead to a performance overhead due to high memory consumption and CPU usage.Ĭoroutines are an alternate way of writing asynchronous programs but are much more lightweight compared to threads. In asynchronous programs, multiple tasks execute in parallel on separate threads without waiting for the other tasks to complete.

Coroutines are a design pattern for writing asynchronous programs for running multiple tasks concurrently.

Kotlin code examples