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Java > Open Source Codes > com > sleepycat > collections > StoredKeySet


1 /*-
2  * See the file LICENSE for redistribution information.
3  *
4  * Copyright (c) 2000,2006 Oracle. All rights reserved.
5  *
6  * $Id: StoredKeySet.java,v 1.31 2006/10/30 21:14:10 bostic Exp $
7  */
8
9 package com.sleepycat.collections;
10
11 import java.util.Set JavaDoc;
12
13 import com.sleepycat.bind.EntryBinding;
14 import com.sleepycat.je.Database;
15 import com.sleepycat.je.DatabaseEntry;
16 import com.sleepycat.je.DatabaseException;
17 import com.sleepycat.je.OperationStatus;
18
19 /**
20  * The Set returned by Map.keySet() and which can also be constructed directly
21  * if a Map is not needed.
22  * Since this collection is a set it only contains one element for each key,
23  * even when duplicates are allowed. Key set iterators are therefore
24  * particularly useful for enumerating the unique keys of a store or index that
25  * allows duplicates.
26  *
27  * @author Mark Hayes
28  */
29 public class StoredKeySet extends StoredCollection implements Set JavaDoc {
30
31     /**
32      * Creates a key set view of a {@link Database}.
33      *
34      * @param database is the Database underlying the new collection.
35      *
36      * @param keyBinding is the binding used to translate between key buffers
37      * and key objects.
38      *
39      * @param writeAllowed is true to create a read-write collection or false
40      * to create a read-only collection.
41      *
42      * @throws IllegalArgumentException if formats are not consistently
43      * defined or a parameter is invalid.
44      *
45      * @throws RuntimeExceptionWrapper if a {@link DatabaseException} is
46      * thrown.
47      */
48     public StoredKeySet(Database database, EntryBinding keyBinding,
49                         boolean writeAllowed) {
50
51         super(new DataView(database, keyBinding, null, null,
52                            writeAllowed, null));
53     }
54
55     StoredKeySet(DataView keySetView) {
56
57         super(keySetView);
58     }
59
60     /**
61      * Adds the specified key to this set if it is not already present
62      * (optional operation).
63      * When a key is added the value in the underlying data store will be
64      * empty.
65      * This method conforms to the {@link Set#add} interface.
66      *
67      * @throws UnsupportedOperationException if the collection is indexed, or
68      * if the collection is read-only.
69      *
70      * @throws RuntimeExceptionWrapper if a {@link DatabaseException} is
71      * thrown.
72      */
73     public boolean add(Object JavaDoc key) {
74
75         DataCursor cursor = null;
76         boolean doAutoCommit = beginAutoCommit();
77         try {
78             cursor = new DataCursor(view, true);
79             OperationStatus status = cursor.putNoOverwrite(key, null, false);
80             closeCursor(cursor);
81             commitAutoCommit(doAutoCommit);
82             return (status == OperationStatus.SUCCESS);
83         } catch (Exception JavaDoc e) {
84             closeCursor(cursor);
85             throw handleException(e, doAutoCommit);
86         }
87     }
88
89     /**
90      * Removes the specified key from this set if it is present (optional
91      * operation).
92      * If duplicates are allowed, this method removes all duplicates for the
93      * given key.
94      * This method conforms to the {@link Set#remove} interface.
95      *
96      * @throws UnsupportedOperationException if the collection is read-only.
97      *
98      * @throws RuntimeExceptionWrapper if a {@link DatabaseException} is
99      * thrown.
100      */
101     public boolean remove(Object JavaDoc key) {
102
103         return removeKey(key, null);
104     }
105
106     /**
107      * Returns true if this set contains the specified key.
108      * This method conforms to the {@link Set#contains} interface.
109      *
110      * @throws RuntimeExceptionWrapper if a {@link DatabaseException} is
111      * thrown.
112      */
113     public boolean contains(Object JavaDoc key) {
114
115         return containsKey(key);
116     }
117
118     boolean hasValues() {
119
120         return false;
121     }
122
123     Object JavaDoc makeIteratorData(BaseIterator iterator,
124                             DatabaseEntry keyEntry,
125                             DatabaseEntry priKeyEntry,
126                             DatabaseEntry valueEntry) {
127
128         return view.makeKey(keyEntry, priKeyEntry);
129     }
130
131     boolean iterateDuplicates() {
132
133         return false;
134     }
135 }
136
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