How to sleep a thread in Clojure

Syntax

You can use the Thread/sleep function to sleep a thread in Clojure. The Thread/sleep function takes a single argument—the number of milliseconds to sleep.

The above statement will cause the thread to sleep for one second. We can modify the time by changing the value.

Code example

Let’s look at an example of how to create a thread that sleeps for three seconds and prints a message:

Note: Try changing the time for the thread to sleep to more than three seconds. You'll notice that the execution time changes when the output is displayed.

Code explanation

• Lines 2–8: We define a function, my-thread-fn, using defn. This function prints two messages, one before the thread sleeps and the one after sleeping the thread for three seconds.

• Line 11: We create a new Thread object using the my-thread-fn function.

• Line 13: We start the thread using the start method.

• Line 15: Wait for the thread to complete using the join method.

Overall, sleeping a thread can be a helpful tool for managing resource usage, introducing delays in program execution, and synchronizing the execution of multiple threads. However, it’s essential to use sleep judiciously, as excessive use of sleep can lead to performance problems and make it difficult to reason about program behavior.