Erro hibernate

oii… estou tentando salvar um obj do tipo professor, que extende pessoa, mas quando tento adicionar da erro:

org.hibernate.PropertyAccessException: IllegalArgumentException occurred while calling setter of Professor.turmas at org.hibernate.property.BasicPropertyAccessor$BasicSetter.set(BasicPropertyAccessor.java:70) at org.hibernate.tuple.AbstractTuplizer.setPropertyValues(AbstractTuplizer.java:207) at org.hibernate.tuple.PojoTuplizer.setPropertyValues(PojoTuplizer.java:176) at org.hibernate.persister.entity.BasicEntityPersister.setPropertyValues(BasicEntityPersister.java:2919) at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:225) at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:160) at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:108) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:184) at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:173) at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:69) at org.hibernate.impl.SessionImpl.save(SessionImpl.java:481) at org.hibernate.impl.SessionImpl.save(SessionImpl.java:476) at org.hibernate.id.ForeignGenerator.generate(ForeignGenerator.java:47) at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:85) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:184) at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:173) at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:69) at org.hibernate.impl.SessionImpl.save(SessionImpl.java:481) at org.hibernate.impl.SessionImpl.save(SessionImpl.java:476) at HibernateTeste.main(HibernateTeste.java:65) Caused by: java.lang.IllegalArgumentException: argument type mismatch at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.hibernate.property.BasicPropertyAccessor$BasicSetter.set(BasicPropertyAccessor.java:40) ... 23 more

o codigo na minha classe eh: [code] public void setTurmas(Turma turma) {
try {
turmas.add(turma);
} catch (Exception e) {
e.printStackTrace();
}

}[/code]

qual o problema???

valeu,

 marci :sad:

argument type mismatch
o tipo passado não corresponde ao esperado

verifique o tipo declarado na interface (caso exista)

verifique o esquema de herança entre as classes Turmas