Your own answer is incorrect. Instead, if you are implementing an interface (or extending a class) which needs to return a Java list, you should do this:
def getAllStudents() : java.util.List[Student] = {
getSession().createQuery("from Student where isDelete = 'false' ")
.list()
}
If you don't need Java list here, then you should instead do
import scala.collection.JavaConverters._
def getAllStudents() : Seq[Student] = {
getSession().createQuery("from Student where isDelete = 'false' ")
.list().asScala
}