Summary

This chapter was a detailed introduction to many important concepts and tools involved in concurrency, and acts as a foundation for the upcoming chapters. So here's a summary to help you remember some of the most important points that we discussed:

• An application has one or more processes; each of them has at least one thread, and coroutines are executed inside a thread.
• A coroutine can be executed in a different thread each time it's resumed, but can also be confined to a specific thread.
• An application is concurrent when its execution happens in more than one overlapping thread.
• To write correct concurrent code, it's necessary to learn how to communicate and synchronize the different threads, which in Kotlin implies the communication and synchronization of coroutines.
• Parallelism happens when, during the execution of a concurrent application, at least two threads are effectively being executed simultaneously.
• Concurrency can happen without parallelism because modern processing units will interleave between threads, effectively overlapping threads.
• There are many challenges when it comes to writing concurrent code, most of them related to correct communication and the synchronization of threads. Race conditions, atomicity violations, deadlocks, and livelocks are examples of the most common challenges.
• Kotlin has taken a modern and fresh approach to concurrency. With Kotlin, it's possible and encouraged to write non-blocking, readable, leveraged, and flexible concurrent code.

In the next chapter, we will work with coroutines. We will start by configuring Android Studio and creating a project that supports coroutines. Then we will write and run concurrent code in an Android emulator, using coroutines for real-world scenarios such as REST calls. We will look at practical examples of suspending functions.