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ARQ is a SPARQL 1.1 query engine for Apache Jena

There is a newer version: 5.1.0

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.sparql.algebra.table;

import java.util.Collections;
import java.util.Iterator ;
import java.util.List ;

import org.apache.jena.atlas.iterator.Iter ;
import org.apache.jena.sparql.algebra.Table ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.engine.ExecutionContext ;
import org.apache.jena.sparql.engine.QueryIterator ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.engine.binding.BindingFactory ;
import org.apache.jena.sparql.engine.iterator.QueryIterSingleton ;

public class TableUnit extends TableBase
{
    static public boolean isTableUnit(Table table)
    { return (table instanceof TableUnit) ; } 
 
    public TableUnit() {}
    
    @Override
    public Iterator rows() {
        Binding binding = BindingFactory.binding() ;
        return Iter.singleton(binding) ;
    }
    
    @Override
    public QueryIterator iterator(ExecutionContext execCxt)
    {
        // BindingRoot?
        Binding binding = BindingFactory.binding() ;
        return QueryIterSingleton.create(binding, execCxt) ;
    }

    @Override
    public void closeTable()    { }

    @Override
    public int size()           { return 1 ; }
    @Override
    public boolean isEmpty()    { return false ; }

    @Override
    public List getVarNames()   { return Collections.emptyList(); }
    @Override
    public List getVars()          { return Collections.emptyList(); }
    
    @Override
    public String toString()    { return "TableUnit" ; }
}