diff --git a/core-java-modules/core-java-concurrency-advanced-4/README.md b/core-java-modules/core-java-concurrency-advanced-4/README.md
index ba838dbc72..808db89b12 100644
--- a/core-java-modules/core-java-concurrency-advanced-4/README.md
+++ b/core-java-modules/core-java-concurrency-advanced-4/README.md
@@ -5,3 +5,4 @@
 - [Start Two Threads at the Exact Same Time in Java](https://www.baeldung.com/java-start-two-threads-at-same-time)
 - [Volatile Variables and Thread Safety](https://www.baeldung.com/java-volatile-variables-thread-safety)
 - [Producer-Consumer Problem With Example in Java](https://www.baeldung.com/java-producer-consumer-problem)
+- [Acquire a Lock by a Key in Java](https://www.baeldung.com/java-acquire-lock-by-key)