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/* Copyright (C) 2004 - 2005  db4objects Inc.  http://www.db4o.com

This file is part of the db4o open source object database.

db4o is free software; you can redistribute it and/or modify it under
the terms of version 2 of the GNU General Public License as published
by the Free Software Foundation and as clarified by db4objects' GPL 
interpretation policy, available at
http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
Suite 350, San Mateo, CA 94403, USA.

db4o 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 General Public License
for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. */
package  com.db4o;

import com.db4o.ext.*;

/**
 * query resultset.
 * 

An ObjectSet is a representation for a set of objects returned 
 * by a query.
 * 

ObjectSet extends the system collection interfaces 
 * java.util.List/System.Collections.IList where they are available. It is
 * recommended, never to reference ObjectSet directly in code but to use
 * List / IList instead.
 * 

Note that the underlying 
 * {@link ObjectContainer ObjectContainer} of an ObjectSet
 * needs to remain open as long as an ObjectSet is used. This is necessary
 * for lazy instantiation. The objects in an ObjectSet are only instantiated
 * when they are actually being used by the application. 
 * @see ExtObjectSet for extended functionality.
 * 
 */
public interface ObjectSet {
	
	
	/**
     * returns an ObjectSet with extended functionality.
     * 

Every ObjectSet that db4o provides can be casted to
     * an ExtObjectSet. This method is supplied for your convenience
     * to work without a cast.
     * 

The ObjectSet functionality is split to two interfaces
     * to allow newcomers to focus on the essential methods.
     */
    public ExtObjectSet ext();
	
	
    /**
	 * returns true if the ObjectSet has more elements.
	 *
     * @return boolean - true if the ObjectSet has more
	 * elements.
     */
    public boolean hasNext ();

    /**
	 * returns the next object in the ObjectSet.
	 * 


	 * Before returning the Object, next() triggers automatic activation of the
	 * Object with the respective
	 * {@link com.db4o.config.Configuration#activationDepth global} or
	 * {@link com.db4o.config.ObjectClass#maximumActivationDepth class specific}
	 * setting.


     * @return the next object in the ObjectSet.
     */
    public Object next ();

    /**
	 * resets the ObjectSet cursor before the first element.
	 * 

A subsequent call to next() will return the first element.
     */
    public void reset ();

    /**
	 * returns the number of elements in the ObjectSet.
     * @return the number of elements in the ObjectSet.
     */
    public int size ();
}