Question: What is the Garbage Collector ZGC + Shenandoah in Java 15?

The requirements for modern applications are becoming increasingly demanding. With memory requirements ranging from gigabytes to terabytes, they may have to achieve response times in the single-digit millisecond range.

Conventional garbage collectors (such as the allrounder G1) with stop-the-world phases of a hundred milliseconds and more are not optimally suited to such requirements.

Aiming to eliminate stop-the-world pauses as much as possible (by doing most of the work in parallel with the running application), or at least reduce them to a few milliseconds, Oracle and RedHat have developed two new garbage collectors that have been shipped as preview features since Java 11 and 12, respectively.

As of Java 15, they are ready for productive use and will hopefully make the Java platform attractive to even more developers.