1/*- 2 * See the file LICENSE for redistribution information. 3 * 4 * Copyright (c) 2000,2008 Oracle. All rights reserved. 5 * 6 * $Id: StoredKeySet.java,v 12.7 2008/01/08 20:58:36 bostic Exp $ 7 */ 8 9package com.sleepycat.collections; 10 11import java.util.Set; 12 13import com.sleepycat.bind.EntryBinding; 14import com.sleepycat.db.Database; 15import com.sleepycat.db.DatabaseEntry; 16import com.sleepycat.db.DatabaseException; 17import com.sleepycat.db.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 */ 29public class StoredKeySet extends StoredCollection implements Set { 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 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 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 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 key) { 114 115 return containsKey(key); 116 } 117 118 boolean hasValues() { 119 120 return false; 121 } 122 123 Object 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