Is there one JVM per Java application?

Generally speaking, each application will get its own JVM instance and its own OS-level process and each JVM instance is independent of each other.

There are some implementation details such as Class Data Sharing, where multiple JVM instances might share some data/memory but those have no user-visible effect to the applications (except for improved startup time, hopefully).

A common scenario however is a single application server (or “web server”) such as Glassfish or Tomcat running multiple web applications. In this case, multiple web applications can share a JVM.

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