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Hibernate example source code file (JoinedIterator.java)

This example Hibernate source code file (JoinedIterator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Hibernate tags/keywords

iterator, iterator, iterators, joinediterator, joinediterator, null, nullpointerexception, nullpointerexception, object, object, unexpected, util

The Hibernate JoinedIterator.java source code

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Middleware LLC.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 *
 */
package org.hibernate.internal.util.collections;

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

/**
 * An JoinedIterator is an Iterator that wraps a number of Iterators.
 *
 * This class makes multiple iterators look like one to the caller.
 * When any method from the Iterator interface is called, the JoinedIterator
 * will delegate to a single underlying Iterator. The JoinedIterator will
 * invoke the Iterators in sequence until all Iterators are exhausted.
 *
 */
public class JoinedIterator implements Iterator {

	private static final Iterator[] ITERATORS = {};

	// wrapped iterators
	private Iterator[] iterators;

	// index of current iterator in the wrapped iterators array
	private int currentIteratorIndex;

	// the current iterator
	private Iterator currentIterator;

	// the last used iterator
	private Iterator lastUsedIterator;

	public JoinedIterator(List iterators) {
		this( (Iterator[]) iterators.toArray(ITERATORS) );
	}

	public JoinedIterator(Iterator[] iterators) {
		if( iterators==null )
			throw new NullPointerException("Unexpected NULL iterators argument");
		this.iterators = iterators;
	}

	public JoinedIterator(Iterator first, Iterator second) {
		this( new Iterator[] { first, second } );
	}

	public boolean hasNext() {
		updateCurrentIterator();
		return currentIterator.hasNext();
	}

	public Object next() {
		updateCurrentIterator();
		return currentIterator.next();
	}

	public void remove() {
		updateCurrentIterator();
		lastUsedIterator.remove();
	}


	// call this before any Iterator method to make sure that the current Iterator
	// is not exhausted
	protected void updateCurrentIterator() {

		if (currentIterator == null) {
			if( iterators.length==0  ) {
				currentIterator = EmptyIterator.INSTANCE;
			}
			else {
				currentIterator = iterators[0];
			}
			// set last used iterator here, in case the user calls remove
			// before calling hasNext() or next() (although they shouldn't)
			lastUsedIterator = currentIterator;
		}

		while (! currentIterator.hasNext() && currentIteratorIndex < iterators.length - 1) {
			currentIteratorIndex++;
			currentIterator = iterators[currentIteratorIndex];
		}
	}

}

Other Hibernate examples (source code examples)

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