Try this way:-
Query myQuery = new Query();
Criteria myCriteria = null;
ItemTypeCriteria isSchema = new ItemTypeCriteria(8);
PublicationCriteria pubCriteria = new PublicationCriteria(251);
AndCriteria andCriteria = new AndCriteria(isSchema, pubCriteria);
myCriteria = andCriteria;
myQuery.setCriteria(myCriteria);
SortParameter sortParameter = new SortParameter(SortParameter.ITEMS_SCHEMA_ID,
SortParameter.ASCENDING);
myQuery.addSorting(sortParameter);
//myQuery.setResultFilter(new LimitFilter(25));
String[] itemResults = myQuery.executeQuery();
System.out.println("RESULTS: " + itemResults.length);
Note that I haven't tested yet