Update javaconcurrent.md

Author: jackbergus

teaching/javaconcurrent.md

@@ -20,8 +20,8 @@ nav_order: 4
 
 ## Previous Topics
 
- * [Theoretical and Practical Introduction to Concurrency](https://drive.google.com/file/d/1dj0Y6bNeHjnrHD1AUA8X0K8UivunPdjq/view?usp=sharing)
- * [(More on) Java Concurrency](https://drive.google.com/file/d/161-BfE8UfM7zbSEBuJ1mr_8JCgwcE5gS/view?usp=sharing)
- * [Critical Sections and Mutual Exclusions](https://drive.google.com/file/d/1jmN-qtsP9b2oXdEj_PqCAC4Hcx6S2ZAi/view?usp=sharing)
- * [Semaphores](https://drive.google.com/file/d/1bVam6aU0126EUbqBKssCJh405fYGz7EU/view?usp=sharing)
- * [Monitors](https://drive.google.com/file/d/1ie7bYu3CcTs1gBJjZUhVv_T1IvLlewq1/view?usp=sharing)
+ * [Theoretical and Practical Introduction to Concurrency](https://drive.google.com/file/d/1dj0Y6bNeHjnrHD1AUA8X0K8UivunPdjq/view?usp=sharing) ([Video](https://youtu.be/-RTKfXGWNIo))
+ * [(More on) Java Concurrency](https://drive.google.com/file/d/161-BfE8UfM7zbSEBuJ1mr_8JCgwcE5gS/view?usp=sharing) ([Video](https://youtu.be/rj6GQ_Vww54))
+ * [Critical Sections and Mutual Exclusions](https://drive.google.com/file/d/1jmN-qtsP9b2oXdEj_PqCAC4Hcx6S2ZAi/view?usp=sharing) ([Video](https://youtu.be/ZABcL-BGSvQ))
+ * [Semaphores](https://drive.google.com/file/d/1bVam6aU0126EUbqBKssCJh405fYGz7EU/view?usp=sharing) ([Video](https://youtu.be/3Ry0FlCsEn0))
+ * [Monitors](https://drive.google.com/file/d/1ie7bYu3CcTs1gBJjZUhVv_T1IvLlewq1/view?usp=sharing) ([Video](https://youtu.be/QnI2Phlu01E))