Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

pinning

A virtual thread that can't leave its carrier while it waits, holding the carrier like a platform thread.

Since JDK 24 (JEP 491) blocking inside synchronized no longer pins; blocking inside native code or a foreign function call still does.