Correctly implementing wait and notify in Kotlin

Question

According to this document, using wait and notify is discouraged in Kotlin: https://kotlinlang.org/docs/reference/java-interop.html

Answer 1

A BlockingQueue can be a suitable high-level concurrency utility for your use case, but applying it requires knowing and modifying your code structure.

The idea is, fetchData() should .take() an item from the queue, and if the queue is empty, that will block the execution until an item appears, which eliminates the .wait() in your code. The producer of the data should .put(t) the data into the queue.

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If you really need to use wait and notify, e.g. for implementing a concurrency utility at low-level, you can cast a Kotlin object to java.lang.Object and call these functions afterwards, as said in the language reference. Or, written as extension functions:

@Suppress("PLATFORM_CLASS_MAPPED_TO_KOTLIN")
private fun Any.wait() = (this as java.lang.Object).wait()