Java FAQ: Top Questions
65. What is Class Data Sharing (CDS) in Java?
Class Data Sharing (CDS) , introduced in Java 5, allows sharing of class metadata across JVM instances to reduce memory usage and startup time.
-
Mechanism:
Stores class metadata in a shared archive (
classes.jsa). - AppCDS: Application CDS (Java 10+) extends CDS to application classes.
-
Usage:
Enabled with
-Xshare:onor-XX:+UseAppCDS. -
Creation:
Generate archive with
-XX:ArchiveClassesAtExit. - Use Case: Microservices, containers, or multi-JVM environments.