001: /*
002: * <copyright>
003: *
004: * Copyright 1997-2004 BBNT Solutions, LLC
005: * under sponsorship of the Defense Advanced Research Projects
006: * Agency (DARPA).
007: *
008: * You can redistribute this software and/or modify it under the
009: * terms of the Cougaar Open Source License as published on the
010: * Cougaar Open Source Website (www.cougaar.org).
011: *
012: * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
013: * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
014: * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
015: * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
016: * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
017: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
018: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
019: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
020: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
021: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
022: * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
023: *
024: * </copyright>
025: */
026:
027: package org.cougaar.lib.util;
028:
029: import java.util.Enumeration;
030: import java.util.Hashtable;
031: import java.util.Map;
032:
033: /**
034: * A class that stores items, keying them by a generated UID.
035: **/
036: public class UIDHashtable extends Hashtable {
037:
038: //CLASS VARIABLES:
039: //////////////////
040: private int nextUID = 0;
041:
042: //CONSTRUCTORS
043: //////////////
044:
045: public UIDHashtable() {
046: super ();
047: }
048:
049: public UIDHashtable(int initialCapacity) {
050: super (initialCapacity);
051: }
052:
053: public UIDHashtable(int initialCapacity, float loadFactor) {
054: super (initialCapacity, loadFactor);
055: }
056:
057: public UIDHashtable(Map t) {
058: super (t);
059: }
060:
061: // OVERLOADED FUNCTIONS:
062: ////////////////////////
063:
064: /**
065: * Function puts a new key/value pair in the table. The key
066: * Better be a Integer that represents a UID that is not already
067: * in the table or an IllegalArgumentException is thrown. The
068: * value better not be in the table already under a different key.
069: * (multiple assignements to the same key are permitted though).
070: **/
071: public synchronized Object put(Object key, Object value)
072: throws IllegalArgumentException {
073:
074: if (!(key instanceof Integer))
075: throw new IllegalArgumentException(
076: "UIDHashTable.put(key,value): key must be an Integer.");
077: Object oldValue = get(key);
078: if (oldValue != null && oldValue.equals(value))
079: return oldValue;
080: else if (oldValue != null)
081: throw new IllegalArgumentException(
082: "UIDHashTable.put(key,value): key must be a valid UID -- "
083: + "Key already present in table.");
084: else if (containsValue(value))
085: throw new IllegalArgumentException(
086: "UIDHashTable.put(key,value): value aready in table under"
087: + "a different key. Value can only in table once.");
088: Object ret = super .put(key, value);
089: ensureNextUIDIsUnique();
090: return ret;
091: }
092:
093: // CLASS FUNCTIONS:
094: ///////////////////
095:
096: /**
097: * Use this function to put an object in the table, and let the table
098: * determine the approriate UID
099: * @param value The object to put in the table. Note value <B>CAN NOT</B>
100: * be null.
101: * @return an Integer that was used as the key.
102: **/
103: public synchronized Integer put(Object value) {
104: Integer ret = keyForValue(value);
105: if (ret != null)
106: return ret;
107: Integer key = new Integer(nextUID);
108: put(key, value);
109: ensureNextUIDIsUnique();
110: return key;
111: }
112:
113: /**
114: * Call this to make sure the nextUID variable is set properly for the next
115: * call to put(Object)
116: **/
117: private synchronized void ensureNextUIDIsUnique() {
118: while (get(new Integer(nextUID)) != null) {
119: nextUID++;
120: if (nextUID == Integer.MAX_VALUE)
121: nextUID = Integer.MIN_VALUE;
122: }
123: }
124:
125: /**
126: * Return the key for the given value
127: * @param value to look for
128: * @return the key for the first entry found that matches the given value
129: **/
130: public synchronized Integer keyForValue(Object value) {
131: Enumeration en = keys();
132: Integer key;
133: while (en.hasMoreElements()) {
134: key = (Integer) en.nextElement();
135: if (get(key).equals(value))
136: return key;
137: }
138: return null;
139: }
140: }
|