ResultSetIterator.java

/*
 * Copyright (c) 2011,2013 Big Switch Networks, Inc.
 *
 * Licensed under the Eclipse Public License, Version 1.0 (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.eclipse.org/legal/epl-v10.html
 *
 * 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.
 *
 * This file incorporates work covered by the following copyright and
 * permission notice:
 *
 *    Originally created by David Erickson, Stanford University 
 *
 *    Licensed 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.sdnplatform.storage;

import java.util.Iterator;
import java.util.NoSuchElementException;

/** Iterator wrapper for an IResultSet, useful for iterating through query
 * results in an enhanced for (foreach) loop.
 * 
 * Note that the iterator manipulates the state of the underlying IResultSet.
 */
public class ResultSetIterator implements Iterator<IResultSet> {
    private IResultSet resultSet;
    private boolean hasAnother;
    private boolean peekedAtNext;
    
    public ResultSetIterator(IResultSet resultSet) {
        this.resultSet = resultSet;
        this.peekedAtNext = false;
    }
    
    @Override
    public IResultSet next() {
        if (!peekedAtNext) {
            hasAnother = resultSet.next();
        }
        peekedAtNext = false;
        if (!hasAnother)
            throw new NoSuchElementException();
        return resultSet;
    }
    
    @Override
    public boolean hasNext() {
        if (!peekedAtNext) {
            hasAnother = resultSet.next();
            peekedAtNext = true;
        }
        return hasAnother;
    }
    
    /** Row removal is not supported; use IResultSet.deleteRow instead.
     */
    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }
}