find(entityClass, primaryKey, properties) - JPA EntityManager's method

T find(
  Class<T> entityClass,
  Object primaryKey,
  Map<String,Object> properties

Find by primary key, using the specified properties. Search for an entity of the specified class and primary key. If the entity instance is contained in the persistence context, it is returned from there. If a vendor-specific property or hint is not recognized, it is silently ignored.
entityClass - entity class
primaryKey - primary key
properties - standard and vendor-specific properties and hints
the found entity instance or null if the entity does not exist
IllegalArgumentException - if the first argument does not denote an entity type or the second argument is is not a valid type for that entity’s primary key or is null
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.