where(restriction) - JPA Subquery's method

Modify the subquery to restrict the result according to the specified boolean expression. Replaces the previously added restriction(s), if any. This method only overrides the return type of the corresponding AbstractQuery method.
restriction - a simple or compound boolean expression
the modified subquery
JPA 2.0

This documentation page is derived (with some adjustments) from the open source JPA 2 RI (EclipseLink)
and is available under the terms of the Eclipse Public License, v. 1.0 and Eclipse Distribution License, v. 1.0.
Object Relational Mapping (ORM) JPA 2 providers include Hibernate, EclipseLink, TopLink, OpenJPA and DataNucleus.
ObjectDB is not an ORM JPA implementation but an Object Database for Java with built in JPA 2 support.