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26 
27 package java.util;
28 
29 import java.util.Map.Entry;
30 
31 /**
32  * A specialized {@link Map} implementation for use with enum type keys.  All
33  * of the keys in an enum map must come from a single enum type that is
34  * specified, explicitly or implicitly, when the map is created.  Enum maps
35  * are represented internally as arrays.  This representation is extremely
36  * compact and efficient.
37  *
38  * <p>Enum maps are maintained in the <i>natural order</i> of their keys
39  * (the order in which the enum constants are declared).  This is reflected
40  * in the iterators returned by the collections views ({@link #keySet()},
41  * {@link #entrySet()}, and {@link #values()}).
42  *
43  * <p>Iterators returned by the collection views are <i>weakly consistent</i>:
44  * they will never throw {@link ConcurrentModificationException} and they may
45  * or may not show the effects of any modifications to the map that occur while
46  * the iteration is in progress.
47  *
48  * <p>Null keys are not permitted.  Attempts to insert a null key will
49  * throw {@link NullPointerException}.  Attempts to test for the
50  * presence of a null key or to remove one will, however, function properly.
51  * Null values are permitted.
52 
53  * <P>Like most collection implementations <tt>EnumMap</tt> is not
54  * synchronized. If multiple threads access an enum map concurrently, and at
55  * least one of the threads modifies the map, it should be synchronized
56  * externally.  This is typically accomplished by synchronizing on some
57  * object that naturally encapsulates the enum map.  If no such object exists,
58  * the map should be "wrapped" using the {@link Collections#synchronizedMap}
59  * method.  This is best done at creation time, to prevent accidental
60  * unsynchronized access:
61  *
62  * <pre>
63  *     Map&lt;EnumKey, V&gt; m
64  *         = Collections.synchronizedMap(new EnumMap&lt;EnumKey, V&gt;(...));
65  * </pre>
66  *
67  * <p>Implementation note: All basic operations execute in constant time.
68  * They are likely (though not guaranteed) to be faster than their
69  * {@link HashMap} counterparts.
70  *
71  * <p>This class is a member of the
72  * <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/collections/index.html">
73  * Java Collections Framework</a>.
74  *
75  * @author Josh Bloch
76  * @see EnumSet
77  * @since 1.5
78  */
79 public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
80     implements java.io.Serializable, Cloneable
81 {
82     /**
83      * The <tt>Class</tt> object for the enum type of all the keys of this map.
84      *
85      * @serial
86      */
87     private final Class<K> keyType;
88 
89     /**
90      * All of the values comprising K.  (Cached for performance.)
91      */
92     private transient K[] keyUniverse;
93 
94     /**
95      * Array representation of this map.  The ith element is the value
96      * to which universe[i] is currently mapped, or null if it isn't
97      * mapped to anything, or NULL if it's mapped to null.
98      */
99     private transient Object[] vals;
100 
101     /**
102      * The number of mappings in this map.
103      */
104     private transient int size = 0;
105 
106     /**
107      * Distinguished non-null value for representing null values.
108      */
109     private static final Object NULL = new Object() {
110         public int hashCode() {
111             return 0;
112         }
113 
114         public String toString() {
115             return "java.util.EnumMap.NULL";
116         }
117     };
118 
maskNull(Object value)119     private Object maskNull(Object value) {
120         return (value == null ? NULL : value);
121     }
122 
123     @SuppressWarnings("unchecked")
unmaskNull(Object value)124     private V unmaskNull(Object value) {
125         return (V)(value == NULL ? null : value);
126     }
127 
128     private static final Enum<?>[] ZERO_LENGTH_ENUM_ARRAY = new Enum<?>[0];
129 
130     /**
131      * Creates an empty enum map with the specified key type.
132      *
133      * @param keyType the class object of the key type for this enum map
134      * @throws NullPointerException if <tt>keyType</tt> is null
135      */
EnumMap(Class<K> keyType)136     public EnumMap(Class<K> keyType) {
137         this.keyType = keyType;
138         keyUniverse = getKeyUniverse(keyType);
139         vals = new Object[keyUniverse.length];
140     }
141 
142     /**
143      * Creates an enum map with the same key type as the specified enum
144      * map, initially containing the same mappings (if any).
145      *
146      * @param m the enum map from which to initialize this enum map
147      * @throws NullPointerException if <tt>m</tt> is null
148      */
EnumMap(EnumMap<K, ? extends V> m)149     public EnumMap(EnumMap<K, ? extends V> m) {
150         keyType = m.keyType;
151         keyUniverse = m.keyUniverse;
152         vals = m.vals.clone();
153         size = m.size;
154     }
155 
156     /**
157      * Creates an enum map initialized from the specified map.  If the
158      * specified map is an <tt>EnumMap</tt> instance, this constructor behaves
159      * identically to {@link #EnumMap(EnumMap)}.  Otherwise, the specified map
160      * must contain at least one mapping (in order to determine the new
161      * enum map's key type).
162      *
163      * @param m the map from which to initialize this enum map
164      * @throws IllegalArgumentException if <tt>m</tt> is not an
165      *     <tt>EnumMap</tt> instance and contains no mappings
166      * @throws NullPointerException if <tt>m</tt> is null
167      */
EnumMap(Map<K, ? extends V> m)168     public EnumMap(Map<K, ? extends V> m) {
169         if (m instanceof EnumMap) {
170             EnumMap<K, ? extends V> em = (EnumMap<K, ? extends V>) m;
171             keyType = em.keyType;
172             keyUniverse = em.keyUniverse;
173             vals = em.vals.clone();
174             size = em.size;
175         } else {
176             if (m.isEmpty())
177                 throw new IllegalArgumentException("Specified map is empty");
178             keyType = m.keySet().iterator().next().getDeclaringClass();
179             keyUniverse = getKeyUniverse(keyType);
180             vals = new Object[keyUniverse.length];
181             putAll(m);
182         }
183     }
184 
185     // Query Operations
186 
187     /**
188      * Returns the number of key-value mappings in this map.
189      *
190      * @return the number of key-value mappings in this map
191      */
size()192     public int size() {
193         return size;
194     }
195 
196     /**
197      * Returns <tt>true</tt> if this map maps one or more keys to the
198      * specified value.
199      *
200      * @param value the value whose presence in this map is to be tested
201      * @return <tt>true</tt> if this map maps one or more keys to this value
202      */
containsValue(Object value)203     public boolean containsValue(Object value) {
204         value = maskNull(value);
205 
206         for (Object val : vals)
207             if (value.equals(val))
208                 return true;
209 
210         return false;
211     }
212 
213     /**
214      * Returns <tt>true</tt> if this map contains a mapping for the specified
215      * key.
216      *
217      * @param key the key whose presence in this map is to be tested
218      * @return <tt>true</tt> if this map contains a mapping for the specified
219      *            key
220      */
containsKey(Object key)221     public boolean containsKey(Object key) {
222         return isValidKey(key) && vals[((Enum<?>)key).ordinal()] != null;
223     }
224 
containsMapping(Object key, Object value)225     private boolean containsMapping(Object key, Object value) {
226         return isValidKey(key) &&
227             maskNull(value).equals(vals[((Enum<?>)key).ordinal()]);
228     }
229 
230     /**
231      * Returns the value to which the specified key is mapped,
232      * or {@code null} if this map contains no mapping for the key.
233      *
234      * <p>More formally, if this map contains a mapping from a key
235      * {@code k} to a value {@code v} such that {@code (key == k)},
236      * then this method returns {@code v}; otherwise it returns
237      * {@code null}.  (There can be at most one such mapping.)
238      *
239      * <p>A return value of {@code null} does not <i>necessarily</i>
240      * indicate that the map contains no mapping for the key; it's also
241      * possible that the map explicitly maps the key to {@code null}.
242      * The {@link #containsKey containsKey} operation may be used to
243      * distinguish these two cases.
244      */
get(Object key)245     public V get(Object key) {
246         return (isValidKey(key) ?
247                 unmaskNull(vals[((Enum<?>)key).ordinal()]) : null);
248     }
249 
250     // Modification Operations
251 
252     /**
253      * Associates the specified value with the specified key in this map.
254      * If the map previously contained a mapping for this key, the old
255      * value is replaced.
256      *
257      * @param key the key with which the specified value is to be associated
258      * @param value the value to be associated with the specified key
259      *
260      * @return the previous value associated with specified key, or
261      *     <tt>null</tt> if there was no mapping for key.  (A <tt>null</tt>
262      *     return can also indicate that the map previously associated
263      *     <tt>null</tt> with the specified key.)
264      * @throws NullPointerException if the specified key is null
265      */
put(K key, V value)266     public V put(K key, V value) {
267         typeCheck(key);
268 
269         int index = key.ordinal();
270         Object oldValue = vals[index];
271         vals[index] = maskNull(value);
272         if (oldValue == null)
273             size++;
274         return unmaskNull(oldValue);
275     }
276 
277     /**
278      * Removes the mapping for this key from this map if present.
279      *
280      * @param key the key whose mapping is to be removed from the map
281      * @return the previous value associated with specified key, or
282      *     <tt>null</tt> if there was no entry for key.  (A <tt>null</tt>
283      *     return can also indicate that the map previously associated
284      *     <tt>null</tt> with the specified key.)
285      */
remove(Object key)286     public V remove(Object key) {
287         if (!isValidKey(key))
288             return null;
289         int index = ((Enum<?>)key).ordinal();
290         Object oldValue = vals[index];
291         vals[index] = null;
292         if (oldValue != null)
293             size--;
294         return unmaskNull(oldValue);
295     }
296 
removeMapping(Object key, Object value)297     private boolean removeMapping(Object key, Object value) {
298         if (!isValidKey(key))
299             return false;
300         int index = ((Enum<?>)key).ordinal();
301         if (maskNull(value).equals(vals[index])) {
302             vals[index] = null;
303             size--;
304             return true;
305         }
306         return false;
307     }
308 
309     /**
310      * Returns true if key is of the proper type to be a key in this
311      * enum map.
312      */
isValidKey(Object key)313     private boolean isValidKey(Object key) {
314         if (key == null)
315             return false;
316 
317         // Cheaper than instanceof Enum followed by getDeclaringClass
318         Class<?> keyClass = key.getClass();
319         return keyClass == keyType || keyClass.getSuperclass() == keyType;
320     }
321 
322     // Bulk Operations
323 
324     /**
325      * Copies all of the mappings from the specified map to this map.
326      * These mappings will replace any mappings that this map had for
327      * any of the keys currently in the specified map.
328      *
329      * @param m the mappings to be stored in this map
330      * @throws NullPointerException the specified map is null, or if
331      *     one or more keys in the specified map are null
332      */
putAll(Map<? extends K, ? extends V> m)333     public void putAll(Map<? extends K, ? extends V> m) {
334         if (m instanceof EnumMap) {
335             EnumMap<?, ?> em = (EnumMap<?, ?>)m;
336             if (em.keyType != keyType) {
337                 if (em.isEmpty())
338                     return;
339                 throw new ClassCastException(em.keyType + " != " + keyType);
340             }
341 
342             for (int i = 0; i < keyUniverse.length; i++) {
343                 Object emValue = em.vals[i];
344                 if (emValue != null) {
345                     if (vals[i] == null)
346                         size++;
347                     vals[i] = emValue;
348                 }
349             }
350         } else {
351             super.putAll(m);
352         }
353     }
354 
355     /**
356      * Removes all mappings from this map.
357      */
clear()358     public void clear() {
359         Arrays.fill(vals, null);
360         size = 0;
361     }
362 
363     // Views
364 
365     /**
366      * This field is initialized to contain an instance of the entry set
367      * view the first time this view is requested.  The view is stateless,
368      * so there's no reason to create more than one.
369      */
370     private transient Set<Map.Entry<K,V>> entrySet;
371 
372     /**
373      * Returns a {@link Set} view of the keys contained in this map.
374      * The returned set obeys the general contract outlined in
375      * {@link Map#keySet()}.  The set's iterator will return the keys
376      * in their natural order (the order in which the enum constants
377      * are declared).
378      *
379      * @return a set view of the keys contained in this enum map
380      */
keySet()381     public Set<K> keySet() {
382         Set<K> ks = keySet;
383         if (ks == null) {
384             ks = new KeySet();
385             keySet = ks;
386         }
387         return ks;
388     }
389 
390     private class KeySet extends AbstractSet<K> {
iterator()391         public Iterator<K> iterator() {
392             return new KeyIterator();
393         }
size()394         public int size() {
395             return size;
396         }
contains(Object o)397         public boolean contains(Object o) {
398             return containsKey(o);
399         }
remove(Object o)400         public boolean remove(Object o) {
401             int oldSize = size;
402             EnumMap.this.remove(o);
403             return size != oldSize;
404         }
clear()405         public void clear() {
406             EnumMap.this.clear();
407         }
408     }
409 
410     /**
411      * Returns a {@link Collection} view of the values contained in this map.
412      * The returned collection obeys the general contract outlined in
413      * {@link Map#values()}.  The collection's iterator will return the
414      * values in the order their corresponding keys appear in map,
415      * which is their natural order (the order in which the enum constants
416      * are declared).
417      *
418      * @return a collection view of the values contained in this map
419      */
values()420     public Collection<V> values() {
421         Collection<V> vs = values;
422         if (vs == null) {
423             vs = new Values();
424             values = vs;
425         }
426         return vs;
427     }
428 
429     private class Values extends AbstractCollection<V> {
iterator()430         public Iterator<V> iterator() {
431             return new ValueIterator();
432         }
size()433         public int size() {
434             return size;
435         }
contains(Object o)436         public boolean contains(Object o) {
437             return containsValue(o);
438         }
remove(Object o)439         public boolean remove(Object o) {
440             o = maskNull(o);
441 
442             for (int i = 0; i < vals.length; i++) {
443                 if (o.equals(vals[i])) {
444                     vals[i] = null;
445                     size--;
446                     return true;
447                 }
448             }
449             return false;
450         }
clear()451         public void clear() {
452             EnumMap.this.clear();
453         }
454     }
455 
456     /**
457      * Returns a {@link Set} view of the mappings contained in this map.
458      * The returned set obeys the general contract outlined in
459      * {@link Map#keySet()}.  The set's iterator will return the
460      * mappings in the order their keys appear in map, which is their
461      * natural order (the order in which the enum constants are declared).
462      *
463      * @return a set view of the mappings contained in this enum map
464      */
entrySet()465     public Set<Map.Entry<K,V>> entrySet() {
466         Set<Map.Entry<K,V>> es = entrySet;
467         if (es != null)
468             return es;
469         else
470             return entrySet = new EntrySet();
471     }
472 
473     private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
iterator()474         public Iterator<Map.Entry<K,V>> iterator() {
475             return new EntryIterator();
476         }
477 
contains(Object o)478         public boolean contains(Object o) {
479             if (!(o instanceof Map.Entry))
480                 return false;
481             Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
482             return containsMapping(entry.getKey(), entry.getValue());
483         }
remove(Object o)484         public boolean remove(Object o) {
485             if (!(o instanceof Map.Entry))
486                 return false;
487             Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
488             return removeMapping(entry.getKey(), entry.getValue());
489         }
size()490         public int size() {
491             return size;
492         }
clear()493         public void clear() {
494             EnumMap.this.clear();
495         }
toArray()496         public Object[] toArray() {
497             return fillEntryArray(new Object[size]);
498         }
499         @SuppressWarnings("unchecked")
toArray(T[] a)500         public <T> T[] toArray(T[] a) {
501             int size = size();
502             if (a.length < size)
503                 a = (T[])java.lang.reflect.Array
504                     .newInstance(a.getClass().getComponentType(), size);
505             if (a.length > size)
506                 a[size] = null;
507             return (T[]) fillEntryArray(a);
508         }
fillEntryArray(Object[] a)509         private Object[] fillEntryArray(Object[] a) {
510             int j = 0;
511             for (int i = 0; i < vals.length; i++)
512                 if (vals[i] != null)
513                     a[j++] = new AbstractMap.SimpleEntry<>(
514                         keyUniverse[i], unmaskNull(vals[i]));
515             return a;
516         }
517     }
518 
519     private abstract class EnumMapIterator<T> implements Iterator<T> {
520         // Lower bound on index of next element to return
521         int index = 0;
522 
523         // Index of last returned element, or -1 if none
524         int lastReturnedIndex = -1;
525 
hasNext()526         public boolean hasNext() {
527             while (index < vals.length && vals[index] == null)
528                 index++;
529             return index != vals.length;
530         }
531 
remove()532         public void remove() {
533             checkLastReturnedIndex();
534 
535             if (vals[lastReturnedIndex] != null) {
536                 vals[lastReturnedIndex] = null;
537                 size--;
538             }
539             lastReturnedIndex = -1;
540         }
541 
checkLastReturnedIndex()542         private void checkLastReturnedIndex() {
543             if (lastReturnedIndex < 0)
544                 throw new IllegalStateException();
545         }
546     }
547 
548     private class KeyIterator extends EnumMapIterator<K> {
next()549         public K next() {
550             if (!hasNext())
551                 throw new NoSuchElementException();
552             lastReturnedIndex = index++;
553             return keyUniverse[lastReturnedIndex];
554         }
555     }
556 
557     private class ValueIterator extends EnumMapIterator<V> {
next()558         public V next() {
559             if (!hasNext())
560                 throw new NoSuchElementException();
561             lastReturnedIndex = index++;
562             return unmaskNull(vals[lastReturnedIndex]);
563         }
564     }
565 
566     private class EntryIterator extends EnumMapIterator<Map.Entry<K,V>> {
567         private Entry lastReturnedEntry;
568 
next()569         public Map.Entry<K,V> next() {
570             if (!hasNext())
571                 throw new NoSuchElementException();
572             lastReturnedEntry = new Entry(index++);
573             return lastReturnedEntry;
574         }
575 
remove()576         public void remove() {
577             lastReturnedIndex =
578                 ((null == lastReturnedEntry) ? -1 : lastReturnedEntry.index);
579             super.remove();
580             lastReturnedEntry.index = lastReturnedIndex;
581             lastReturnedEntry = null;
582         }
583 
584         private class Entry implements Map.Entry<K,V> {
585             private int index;
586 
Entry(int index)587             private Entry(int index) {
588                 this.index = index;
589             }
590 
getKey()591             public K getKey() {
592                 checkIndexForEntryUse();
593                 return keyUniverse[index];
594             }
595 
getValue()596             public V getValue() {
597                 checkIndexForEntryUse();
598                 return unmaskNull(vals[index]);
599             }
600 
setValue(V value)601             public V setValue(V value) {
602                 checkIndexForEntryUse();
603                 V oldValue = unmaskNull(vals[index]);
604                 vals[index] = maskNull(value);
605                 return oldValue;
606             }
607 
equals(Object o)608             public boolean equals(Object o) {
609                 if (index < 0)
610                     return o == this;
611 
612                 if (!(o instanceof Map.Entry))
613                     return false;
614 
615                 Map.Entry<?,?> e = (Map.Entry<?,?>)o;
616                 V ourValue = unmaskNull(vals[index]);
617                 Object hisValue = e.getValue();
618                 return (e.getKey() == keyUniverse[index] &&
619                         (ourValue == hisValue ||
620                          (ourValue != null && ourValue.equals(hisValue))));
621             }
622 
hashCode()623             public int hashCode() {
624                 if (index < 0)
625                     return super.hashCode();
626 
627                 return entryHashCode(index);
628             }
629 
toString()630             public String toString() {
631                 if (index < 0)
632                     return super.toString();
633 
634                 return keyUniverse[index] + "="
635                     + unmaskNull(vals[index]);
636             }
637 
checkIndexForEntryUse()638             private void checkIndexForEntryUse() {
639                 if (index < 0)
640                     throw new IllegalStateException("Entry was removed");
641             }
642         }
643     }
644 
645     // Comparison and hashing
646 
647     /**
648      * Compares the specified object with this map for equality.  Returns
649      * <tt>true</tt> if the given object is also a map and the two maps
650      * represent the same mappings, as specified in the {@link
651      * Map#equals(Object)} contract.
652      *
653      * @param o the object to be compared for equality with this map
654      * @return <tt>true</tt> if the specified object is equal to this map
655      */
equals(Object o)656     public boolean equals(Object o) {
657         if (this == o)
658             return true;
659         if (o instanceof EnumMap)
660             return equals((EnumMap<?,?>)o);
661         if (!(o instanceof Map))
662             return false;
663 
664         Map<?,?> m = (Map<?,?>)o;
665         if (size != m.size())
666             return false;
667 
668         for (int i = 0; i < keyUniverse.length; i++) {
669             if (null != vals[i]) {
670                 K key = keyUniverse[i];
671                 V value = unmaskNull(vals[i]);
672                 if (null == value) {
673                     if (!((null == m.get(key)) && m.containsKey(key)))
674                        return false;
675                 } else {
676                    if (!value.equals(m.get(key)))
677                       return false;
678                 }
679             }
680         }
681 
682         return true;
683     }
684 
equals(EnumMap<?,?> em)685     private boolean equals(EnumMap<?,?> em) {
686         if (em.keyType != keyType)
687             return size == 0 && em.size == 0;
688 
689         // Key types match, compare each value
690         for (int i = 0; i < keyUniverse.length; i++) {
691             Object ourValue =    vals[i];
692             Object hisValue = em.vals[i];
693             if (hisValue != ourValue &&
694                 (hisValue == null || !hisValue.equals(ourValue)))
695                 return false;
696         }
697         return true;
698     }
699 
700     /**
701      * Returns the hash code value for this map.  The hash code of a map is
702      * defined to be the sum of the hash codes of each entry in the map.
703      */
hashCode()704     public int hashCode() {
705         int h = 0;
706 
707         for (int i = 0; i < keyUniverse.length; i++) {
708             if (null != vals[i]) {
709                 h += entryHashCode(i);
710             }
711         }
712 
713         return h;
714     }
715 
entryHashCode(int index)716     private int entryHashCode(int index) {
717         return (keyUniverse[index].hashCode() ^ vals[index].hashCode());
718     }
719 
720     /**
721      * Returns a shallow copy of this enum map.  (The values themselves
722      * are not cloned.
723      *
724      * @return a shallow copy of this enum map
725      */
726     @SuppressWarnings("unchecked")
clone()727     public EnumMap<K, V> clone() {
728         EnumMap<K, V> result = null;
729         try {
730             result = (EnumMap<K, V>) super.clone();
731         } catch(CloneNotSupportedException e) {
732             throw new AssertionError();
733         }
734         result.vals = result.vals.clone();
735         result.entrySet = null;
736         return result;
737     }
738 
739     /**
740      * Throws an exception if e is not of the correct type for this enum set.
741      */
typeCheck(K key)742     private void typeCheck(K key) {
743         Class<?> keyClass = key.getClass();
744         if (keyClass != keyType && keyClass.getSuperclass() != keyType)
745             throw new ClassCastException(keyClass + " != " + keyType);
746     }
747 
748     /**
749      * Returns all of the values comprising K.
750      * The result is uncloned, cached, and shared by all callers.
751      */
getKeyUniverse(Class<K> keyType)752     private static <K extends Enum<K>> K[] getKeyUniverse(Class<K> keyType) {
753         // Android-changed: Use getEnumConstantsShared directly instead of going
754         // through SharedSecrets.
755         return keyType.getEnumConstantsShared();
756     }
757 
758     private static final long serialVersionUID = 458661240069192865L;
759 
760     /**
761      * Save the state of the <tt>EnumMap</tt> instance to a stream (i.e.,
762      * serialize it).
763      *
764      * @serialData The <i>size</i> of the enum map (the number of key-value
765      *             mappings) is emitted (int), followed by the key (Object)
766      *             and value (Object) for each key-value mapping represented
767      *             by the enum map.
768      */
writeObject(java.io.ObjectOutputStream s)769     private void writeObject(java.io.ObjectOutputStream s)
770         throws java.io.IOException
771     {
772         // Write out the key type and any hidden stuff
773         s.defaultWriteObject();
774 
775         // Write out size (number of Mappings)
776         s.writeInt(size);
777 
778         // Write out keys and values (alternating)
779         int entriesToBeWritten = size;
780         for (int i = 0; entriesToBeWritten > 0; i++) {
781             if (null != vals[i]) {
782                 s.writeObject(keyUniverse[i]);
783                 s.writeObject(unmaskNull(vals[i]));
784                 entriesToBeWritten--;
785             }
786         }
787     }
788 
789     /**
790      * Reconstitute the <tt>EnumMap</tt> instance from a stream (i.e.,
791      * deserialize it).
792      */
793     @SuppressWarnings("unchecked")
readObject(java.io.ObjectInputStream s)794     private void readObject(java.io.ObjectInputStream s)
795         throws java.io.IOException, ClassNotFoundException
796     {
797         // Read in the key type and any hidden stuff
798         s.defaultReadObject();
799 
800         keyUniverse = getKeyUniverse(keyType);
801         vals = new Object[keyUniverse.length];
802 
803         // Read in size (number of Mappings)
804         int size = s.readInt();
805 
806         // Read the keys and values, and put the mappings in the HashMap
807         for (int i = 0; i < size; i++) {
808             K key = (K) s.readObject();
809             V value = (V) s.readObject();
810             put(key, value);
811         }
812     }
813 }
814