Author: michiel
Date: 2009-05-18 19:04:25 +0200 (Mon, 18 May 2009)
New Revision: 35272
Added:
mmbase/trunk/src/org/mmbase/util/BijectiveMap.java
Log:
A utitily structure which can come in handy
Added: mmbase/trunk/src/org/mmbase/util/BijectiveMap.java
===================================================================
--- mmbase/trunk/src/org/mmbase/util/BijectiveMap.java
(rev 0)
+++ mmbase/trunk/src/org/mmbase/util/BijectiveMap.java 2009-05-18 17:04:25 UTC
(rev 35272)
@@ -0,0 +1,84 @@
+package org.mmbase.util;
+
+import java.util.*;
+
+/**
+ * A map representing a 1-1 bijective relation between 2 sets of values.
+ *
+ * @author Michiel Meeuwissen
+ * @since MMBase-1.9.1
+ * @version $Id$
+ */
+
+
+public class BijectiveMap<K, V> extends AbstractMap<K, V> {
+
+ private final Map<K, V> backing;
+ private final Map<V, K> inverse;
+
+ public BijectiveMap() {
+ backing = new HashMap<K, V>();
+ inverse = new HashMap<V, K>();
+ }
+ private BijectiveMap(Map<K, V> backing, Map<V, K> inverse) {
+ this.backing = backing;
+ this.inverse = inverse;
+ }
+
+ @Override
+ public Set<Map.Entry<K, V>> entrySet() {
+ return new AbstractSet<Map.Entry<K, V>>() {
+ @Override
+ public int size() {
+ return backing.size();
+ }
+ @Override
+ public Iterator<Map.Entry<K, V>> iterator() {
+ return new Iterator<Map.Entry<K, V>>() {
+ private final Iterator<Map.Entry<K, V>> i =
backing.entrySet().iterator();
+ private Map.Entry<K, V> entry;
+ public boolean hasNext() {
+ return i.hasNext();
+ }
+ public Map.Entry<K, V> next() {
+ entry = i.next();
+ return entry;
+ }
+ public void remove() {
+ i.remove();
+ inverse.remove(entry.getValue());
+
+ }
+ };
+ }
+ };
+ }
+
+ @Override
+ public V put(K key, V value) {
+ if (backing.containsKey(key)) {
+ V prevValue = backing.get(key);
+ if (! prevValue.equals(value)) {
+ if (inverse.containsKey(value)) throw new
IllegalArgumentException();
+ inverse.remove(prevValue);
+ inverse.put(value, key);
+ backing.put(key, value);
+ }
+ return prevValue;
+ } else {
+ if (inverse.containsKey(value)) {
+ throw new IllegalArgumentException("Cannot put " + key + "->"
+ value + " Because the value already exists " + inverse);
+ }
+ backing.put(key, value);
+ inverse.put(value, key);
+ return null;
+ }
+ }
+
+ public K inverseGet(V value) {
+ return inverse.get(value);
+ }
+ public Map<V, K> getInverse() {
+ return new BijectiveMap<V, K>(inverse, backing);
+ }
+}
Property changes on: mmbase/trunk/src/org/mmbase/util/BijectiveMap.java
___________________________________________________________________
Name: svn:keywords
+ Id
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