Coroutines in Kotlin

Need of Coroutines

Coroutines in Kotlin are lightweight, concurrent programming constructs that enable asynchronous operations without the complexity of traditional threads. They introduce the concept of suspending functions, allowing the pausing of execution without blocking the entire thread. Coroutines provide a structured and readable approach to handling asynchronous tasks, enhancing code clarity and maintainability in Kotlin applications.

Android developers wield an array of asynchronous tools, including RxJava, AsyncTasks, Jobs, and Threads. However, the quest for an efficient and readable solution persists, prompting the need to explore new paradigms like coroutines in Kotlin.

While RxJava demands significant effort to master and use safely, AsyncTasks and threads can inadvertently introduce leaks and memory overhead. Despite these drawbacks, reliance on these tools often results in code littered with callbacks, diminishing readability and, subsequently, user experience.

Android, predominantly a single-threaded platform, runs everything on the main thread by default. Without coroutines in Kotlin, developers traditionally offload non-UI tasks to different threads, necessitating procedures with callbacks for result passing. This approach results in bloated code and increased waiting times for results, impacting the responsiveness and user experience.

Coroutines in Kotlin offer a more straightforward syntax, making code more readable and maintaining the expressiveness of the language. Coroutines excel in scenarios where simplicity and ease of use are crucial, providing a pragmatic alternative to RxJava for certain use cases.Embracing coroutines in Kotlin offers a more elegant and streamlined solution, enhancing both code clarity and overall application performance.

Types of Coroutines

Coroutines are of the following types:

Stackful Coroutines:

Description: Stackful coroutines maintain their own call stack, allowing them to capture and restore the entire execution context, including local variables and function calls.

Use Case: Well-suited for scenarios where preserving the entire execution context is essential, such as when dealing with long-running computations or maintaining a consistent state across suspension points.

Stackless Coroutines:

Description: Stackless coroutines, on the other hand, do not carry their own call stack. They rely on the underlying infrastructure (like the thread or the runtime environment) for managing the execution context.

Use Case: Ideal for scenarios where the lightweight nature of coroutines is prioritized, and preserving the entire call stack is not necessary. Stackless coroutines are often more memory-efficient and can be suitable for high concurrency scenarios.

Kotlin Stackless Coroutines

Coroutines in Kotlin are stackless by default. In stackless coroutines, the coroutine itself does not carry its own call stack. Instead, it relies on the underlying infrastructure, such as the Kotlin runtime and the host thread, to manage the execution context. This design makes stackless coroutines more memory-efficient and suitable for scenarios where lightweight concurrency is a priority.

In stackless coroutines, when a coroutine is suspended and later resumed, it doesn't preserve its entire call stack. The runtime takes care of storing and restoring the necessary state, allowing for efficient handling of large numbers of concurrent coroutines without incurring excessive memory overhead.

Overall, stackless coroutines in Kotlin provide a balance between lightweight execution and efficient memory usage, making them well-suited for scenarios where high concurrency and resource efficiency are crucial.

Kotlin Coroutines Features

Coroutines in Kotlin have the following features:

• Lightweight: Coroutines are lightweight, allowing the execution of numerous coroutines on a single thread. Their support for suspension prevents thread blocking, promoting memory efficiency while facilitating multiple concurrent operations.
• Built-in Cancellation Support: Automatic cancellation is inherent in coroutines, managed seamlessly within the running coroutine hierarchy. This feature simplifies the handling of task termination and resource cleanup.
• Fewer Memory Leaks: Coroutines use structured concurrency, confining operations within a scope. This approach minimizes the likelihood of memory leaks, contributing to more robust and memory-efficient code.
• Jetpack Integration: Coroutines seamlessly integrate with Jetpack libraries, offering full support. Many Jetpack libraries include extensions tailored for coroutines, and some even provide dedicated coroutine scopes for structured concurrency. This integration enhances the compatibility and ease of use of coroutines within the Android ecosystem.

Kotlin Coroutines vs Threads

Here the the key differences between threads & coroutines in Kotlin.

1. In comparing coroutines in Kotlin with traditional threads, the process of fetching data from one thread and passing it to another introduces time delays and a convoluted structure with numerous callbacks, diminishing code readability. Coroutines, in contrast, eliminate the need for callbacks.
2. While creating and halting threads is resource-intensive due to the creation of individual stacks, coroutines in Kotlin prove remarkably inexpensive in comparison, with the added advantage of not maintaining their own stack.
3. Threads operate in a blocking manner, rendering the entire thread inactive during sleep periods. Conversely, coroutines in Kotlin, being suspendable, can efficiently perform other tasks during delays, enhancing overall concurrency.
4. Coroutines in Kotlin excel in concurrency, outperforming threads due to reduced blocking and faster context switching. Unlike threads, coroutines can change context at any point, contributing to their agility and speed.
5. Coroutines in Kotlin, managed by users rather than the operating system, offer superior speed compared to threads. The collaboration of thousands of coroutines proves more efficient than a similar number of threads, making coroutines the preferred choice for achieving high concurrency in Kotlin applications.

Kotlin Coroutines Dependencies

Include the following dependencies in the app-level build.gradle file of your Kotlin project.

Code:

Kotlin Coroutines Examples

Consider a scenario where we aim to retrieve student data from a database and display it on the screen. This involves executing a network call, fetching the student from the database, and subsequently presenting it on the screen. The process of fetching the user can be accomplished using either callbacks or coroutines in Kotlin.

Using Callbacks

Code:

Using Coroutines

Code:

As previously mentioned, using callbacks can lead to a decrease in code readability. Therefore, opting for coroutines is a better choice, enhancing both readability and performance. Coroutines in Kotlin offer several advantages beyond the absence of callbacks, including non-blocking behavior, simplicity, and cost-effectiveness in creation. In a nutshell, coroutines in Kotlin provide a more streamlined and efficient approach to asynchronous programming compared to the use of callbacks.