How can Jena be used to save triples in a SPARQL endpoint?
I could use SPARQL RestFul API but I wonder if this is also doable using Jena classes.
For SPARQL Update you can do the following:
UpdateRequest update = UpdateFactory.create("# Your SPARQL Updates");
UpdateProcessor processor = UpdateExecutionFactory.createRemote(update, "http://your-domain/update");
processor.execute();
If you are talking about the graph store protocol i.e. uploading entire graphs at once then you can use the DatasetAccessor API e.g.
DatasetAccessor accessor = DatasetAccessorFactory.createHTTP("http://your-domain/ds");
accessor.putModel(m);
If you are talking about MarkLogic specifically (you tagged the question with marklogic), then this github project will likely interest you:
https://github.com/marklogic/marklogic-jena
This library integrates MarkLogic Semantics feature into the Jena RDF Framework as a persistence and query layer.
Note: not officially released yet currently, but close. Might be worth a look..
HTH!