ObjectDB version 2.5.5 (and above) supports Java 8 (JDK 1.8).
Tracking changes to collections and maps using some new Java 8 methods is currently not fully supported.
The main known issue is that orphan removal does not happen as a result of removing a reference to an object (which becomes an orphan) using the new methods: removeIf(predicate) and remove(key, value).
ObjectDB Support