JDK 21: Not Yet Released - Latest Version is JDK 17

As of September 2021, there is no JDK 21 released by Oracle. The latest major version of JDK (Java Development Kit) is JDK 17, which was released on September 14, 2021.

Oracle typically releases a new major version of JDK every six months, with the next expected release being JDK 18 in March 2022.

It's worth noting that Oracle's JDK is not the only implementation of Java, and there are other vendors who offer their own JDKs with different features and release cycles.