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Java > Open Source Codes > com > db4o > ObjectSet


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o;
22
23 import com.db4o.ext.*;
24
25 /**
26  * query resultset.
27  * <br><br>An ObjectSet is a representation for a set of objects returned
28  * by a query.
29  * <br><br>ObjectSet extends the system collection interfaces
30  * java.util.List/System.Collections.IList where they are available. It is
31  * recommended, never to reference ObjectSet directly in code but to use
32  * List / IList instead.
33  * <br><br>Note that the underlying
34  * {@link ObjectContainer ObjectContainer} of an ObjectSet
35  * needs to remain open as long as an ObjectSet is used. This is necessary
36  * for lazy instantiation. The objects in an ObjectSet are only instantiated
37  * when they are actually being used by the application.
38  * @see ExtObjectSet for extended functionality.
39  *
40  * @sharpen.extends System.Collections.IList
41  */
42 public interface ObjectSet {
43     
44     
45     /**
46      * returns an ObjectSet with extended functionality.
47      * <br><br>Every ObjectSet that db4o provides can be casted to
48      * an ExtObjectSet. This method is supplied for your convenience
49      * to work without a cast.
50      * <br><br>The ObjectSet functionality is split to two interfaces
51      * to allow newcomers to focus on the essential methods.
52      */
53     public ExtObjectSet ext();
54     
55     
56     /**
57      * returns <code>true</code> if the <code>ObjectSet</code> has more elements.
58      *
59      * @return boolean - <code>true</code> if the <code>ObjectSet</code> has more
60      * elements.
61      */
62     public boolean hasNext ();
63
64     /**
65      * returns the next object in the <code>ObjectSet</code>.
66      * <br><br>
67      * Before returning the Object, next() triggers automatic activation of the
68      * Object with the respective
69      * {@link com.db4o.config.Configuration#activationDepth global} or
70      * {@link com.db4o.config.ObjectClass#maximumActivationDepth class specific}
71      * setting.<br><br>
72      * @return the next object in the <code>ObjectSet</code>.
73      */
74     public Object JavaDoc next ();
75
76     /**
77      * resets the <code>ObjectSet</code> cursor before the first element.
78      * <br><br>A subsequent call to <code>next()</code> will return the first element.
79      */
80     public void reset ();
81
82     /**
83      * returns the number of elements in the <code>ObjectSet</code>.
84      * @return the number of elements in the <code>ObjectSet</code>.
85      */
86     public int size ();
87 }
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