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RDF2go is an implementation-independent Java API with the design goals: portability (hence the name), performance and ease of implementation. This project was started at FZI Forschungszentrum Informatik Karlsruhe, Germany - www.fzi.de

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/**
 * LICENSE INFORMATION
 * 
 * Copyright 2005-2008 by FZI (http://www.fzi.de). Licensed under a BSD license
 * (http://www.opensource.org/licenses/bsd-license.php)  = Max Völkel
 *  = FZI Forschungszentrum Informatik Karlsruhe, Karlsruhe,
 * Germany  = 2010
 * 
 * Further project information at http://semanticweb.org/wiki/RDF2Go
 */

package org.ontoware.rdf2go.util;

import java.util.Collection;
import java.util.Iterator;

import org.ontoware.aifbcommons.collection.ClosableIterator;


/**
 * This class consists exclusively of static methods that operate on or return
 * iterators. It is the Iterator-equivalent of java.util.Collections.
 * 
 * copied into RDF2Go by Leo Sauemann on 11.1.2007, it helps to get working
 * quicker.
 */
public class Iterators {
	
	/**
	 * Adds all elements from the supplied iterator to the specified collection.
	 * If the supplied iterator is an instance of {@link ClosableIterator} it is
	 * automatically closed after consumption.
	 * 
	 * @param iter An iterator containing elements to add to the container. If
	 *            the iterator is an instance of {@link ClosableIterator} it is
	 *            automatically closed after consumption.
	 * @param collection The collection to add the elements to.
	 * @return The collection object that was supplied to this method.
	 */
	public static > C addAll(Iterator iter, C collection) {
		try {
			while(iter.hasNext()) {
				collection.add(iter.next());
			}
		} finally {
			closeCloseable(iter);
		}
		
		return collection;
	}
	
	/**
	 * Closes the supplied iterator if it is an instance of
	 * {@link ClosableIterator}, otherwise the request is ignored.
	 * 
	 * @param iter The iterator that should be closed.
	 */
	public static void closeCloseable(Iterator iter) {
		if(iter instanceof ClosableIterator) {
			((ClosableIterator)iter).close();
		}
	}
	
	/**
	 * Converts an iterator to a string by concatenating all of the string
	 * representations of objects in the iterator, divided by a separator.
	 * 
	 * @param iter An iterator over arbitrary objects that are expected to
	 *            implement {@link Object#toString()}.
	 * @param separator The separator to insert between the object strings.
	 * @return A String representation of the objects provided by the supplied
	 *         iterator.
	 */
	public static String toString(Iterator iter, String separator) {
		StringBuilder sb = new StringBuilder();
		toString(iter, separator, sb);
		return sb.toString();
	}
	
	/**
	 * Converts an iterator to a string by concatenating all of the string
	 * representations of objects in the iterator, divided by a separator.
	 * 
	 * @param iter An iterator over arbitrary objects that are expected to
	 *            implement {@link Object#toString()}.
	 * @param separator The separator to insert between the object strings.
	 * @param sb A StringBuilder to append the iterator string to.
	 */
	public static void toString(Iterator iter, String separator, StringBuilder sb) {
		while(iter.hasNext()) {
			sb.append(iter.next());
			
			if(iter.hasNext()) {
				sb.append(separator);
			}
		}
	}
	
	/**
	 * Runs through the iterator and returns number of items. It doesn't close
	 * it.
	 * 
	 * @author clemente
	 * 
	 * @param it Any type of iterator, not null
	 * @returns Number of items
	 */
	
	public static int count(Iterator it) {
		assert it != null;
		
		int count = 0;
		while(it.hasNext()) {
			count++;
			it.next();
		}
		
		return count;
		
	}
	
}