src/java.base/share/classes/java/util/EnumMap.java
changeset 47216 71c04702a3d5
parent 44743 f0bbd698c486
child 49433 b6671a111395
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/java/util/EnumMap.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,812 @@
+/*
+ * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.util;
+
+import jdk.internal.misc.SharedSecrets;
+
+/**
+ * A specialized {@link Map} implementation for use with enum type keys.  All
+ * of the keys in an enum map must come from a single enum type that is
+ * specified, explicitly or implicitly, when the map is created.  Enum maps
+ * are represented internally as arrays.  This representation is extremely
+ * compact and efficient.
+ *
+ * <p>Enum maps are maintained in the <i>natural order</i> of their keys
+ * (the order in which the enum constants are declared).  This is reflected
+ * in the iterators returned by the collections views ({@link #keySet()},
+ * {@link #entrySet()}, and {@link #values()}).
+ *
+ * <p>Iterators returned by the collection views are <i>weakly consistent</i>:
+ * they will never throw {@link ConcurrentModificationException} and they may
+ * or may not show the effects of any modifications to the map that occur while
+ * the iteration is in progress.
+ *
+ * <p>Null keys are not permitted.  Attempts to insert a null key will
+ * throw {@link NullPointerException}.  Attempts to test for the
+ * presence of a null key or to remove one will, however, function properly.
+ * Null values are permitted.
+
+ * <P>Like most collection implementations {@code EnumMap} is not
+ * synchronized. If multiple threads access an enum map concurrently, and at
+ * least one of the threads modifies the map, it should be synchronized
+ * externally.  This is typically accomplished by synchronizing on some
+ * object that naturally encapsulates the enum map.  If no such object exists,
+ * the map should be "wrapped" using the {@link Collections#synchronizedMap}
+ * method.  This is best done at creation time, to prevent accidental
+ * unsynchronized access:
+ *
+ * <pre>
+ *     Map&lt;EnumKey, V&gt; m
+ *         = Collections.synchronizedMap(new EnumMap&lt;EnumKey, V&gt;(...));
+ * </pre>
+ *
+ * <p>Implementation note: All basic operations execute in constant time.
+ * They are likely (though not guaranteed) to be faster than their
+ * {@link HashMap} counterparts.
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @author Josh Bloch
+ * @see EnumSet
+ * @since 1.5
+ */
+public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
+    implements java.io.Serializable, Cloneable
+{
+    /**
+     * The {@code Class} object for the enum type of all the keys of this map.
+     *
+     * @serial
+     */
+    private final Class<K> keyType;
+
+    /**
+     * All of the values comprising K.  (Cached for performance.)
+     */
+    private transient K[] keyUniverse;
+
+    /**
+     * Array representation of this map.  The ith element is the value
+     * to which universe[i] is currently mapped, or null if it isn't
+     * mapped to anything, or NULL if it's mapped to null.
+     */
+    private transient Object[] vals;
+
+    /**
+     * The number of mappings in this map.
+     */
+    private transient int size = 0;
+
+    /**
+     * Distinguished non-null value for representing null values.
+     */
+    private static final Object NULL = new Object() {
+        public int hashCode() {
+            return 0;
+        }
+
+        public String toString() {
+            return "java.util.EnumMap.NULL";
+        }
+    };
+
+    private Object maskNull(Object value) {
+        return (value == null ? NULL : value);
+    }
+
+    @SuppressWarnings("unchecked")
+    private V unmaskNull(Object value) {
+        return (V)(value == NULL ? null : value);
+    }
+
+    /**
+     * Creates an empty enum map with the specified key type.
+     *
+     * @param keyType the class object of the key type for this enum map
+     * @throws NullPointerException if {@code keyType} is null
+     */
+    public EnumMap(Class<K> keyType) {
+        this.keyType = keyType;
+        keyUniverse = getKeyUniverse(keyType);
+        vals = new Object[keyUniverse.length];
+    }
+
+    /**
+     * Creates an enum map with the same key type as the specified enum
+     * map, initially containing the same mappings (if any).
+     *
+     * @param m the enum map from which to initialize this enum map
+     * @throws NullPointerException if {@code m} is null
+     */
+    public EnumMap(EnumMap<K, ? extends V> m) {
+        keyType = m.keyType;
+        keyUniverse = m.keyUniverse;
+        vals = m.vals.clone();
+        size = m.size;
+    }
+
+    /**
+     * Creates an enum map initialized from the specified map.  If the
+     * specified map is an {@code EnumMap} instance, this constructor behaves
+     * identically to {@link #EnumMap(EnumMap)}.  Otherwise, the specified map
+     * must contain at least one mapping (in order to determine the new
+     * enum map's key type).
+     *
+     * @param m the map from which to initialize this enum map
+     * @throws IllegalArgumentException if {@code m} is not an
+     *     {@code EnumMap} instance and contains no mappings
+     * @throws NullPointerException if {@code m} is null
+     */
+    public EnumMap(Map<K, ? extends V> m) {
+        if (m instanceof EnumMap) {
+            EnumMap<K, ? extends V> em = (EnumMap<K, ? extends V>) m;
+            keyType = em.keyType;
+            keyUniverse = em.keyUniverse;
+            vals = em.vals.clone();
+            size = em.size;
+        } else {
+            if (m.isEmpty())
+                throw new IllegalArgumentException("Specified map is empty");
+            keyType = m.keySet().iterator().next().getDeclaringClass();
+            keyUniverse = getKeyUniverse(keyType);
+            vals = new Object[keyUniverse.length];
+            putAll(m);
+        }
+    }
+
+    // Query Operations
+
+    /**
+     * Returns the number of key-value mappings in this map.
+     *
+     * @return the number of key-value mappings in this map
+     */
+    public int size() {
+        return size;
+    }
+
+    /**
+     * Returns {@code true} if this map maps one or more keys to the
+     * specified value.
+     *
+     * @param value the value whose presence in this map is to be tested
+     * @return {@code true} if this map maps one or more keys to this value
+     */
+    public boolean containsValue(Object value) {
+        value = maskNull(value);
+
+        for (Object val : vals)
+            if (value.equals(val))
+                return true;
+
+        return false;
+    }
+
+    /**
+     * Returns {@code true} if this map contains a mapping for the specified
+     * key.
+     *
+     * @param key the key whose presence in this map is to be tested
+     * @return {@code true} if this map contains a mapping for the specified
+     *            key
+     */
+    public boolean containsKey(Object key) {
+        return isValidKey(key) && vals[((Enum<?>)key).ordinal()] != null;
+    }
+
+    private boolean containsMapping(Object key, Object value) {
+        return isValidKey(key) &&
+            maskNull(value).equals(vals[((Enum<?>)key).ordinal()]);
+    }
+
+    /**
+     * Returns the value to which the specified key is mapped,
+     * or {@code null} if this map contains no mapping for the key.
+     *
+     * <p>More formally, if this map contains a mapping from a key
+     * {@code k} to a value {@code v} such that {@code (key == k)},
+     * then this method returns {@code v}; otherwise it returns
+     * {@code null}.  (There can be at most one such mapping.)
+     *
+     * <p>A return value of {@code null} does not <i>necessarily</i>
+     * indicate that the map contains no mapping for the key; it's also
+     * possible that the map explicitly maps the key to {@code null}.
+     * The {@link #containsKey containsKey} operation may be used to
+     * distinguish these two cases.
+     */
+    public V get(Object key) {
+        return (isValidKey(key) ?
+                unmaskNull(vals[((Enum<?>)key).ordinal()]) : null);
+    }
+
+    // Modification Operations
+
+    /**
+     * Associates the specified value with the specified key in this map.
+     * If the map previously contained a mapping for this key, the old
+     * value is replaced.
+     *
+     * @param key the key with which the specified value is to be associated
+     * @param value the value to be associated with the specified key
+     *
+     * @return the previous value associated with specified key, or
+     *     {@code null} if there was no mapping for key.  (A {@code null}
+     *     return can also indicate that the map previously associated
+     *     {@code null} with the specified key.)
+     * @throws NullPointerException if the specified key is null
+     */
+    public V put(K key, V value) {
+        typeCheck(key);
+
+        int index = key.ordinal();
+        Object oldValue = vals[index];
+        vals[index] = maskNull(value);
+        if (oldValue == null)
+            size++;
+        return unmaskNull(oldValue);
+    }
+
+    /**
+     * Removes the mapping for this key from this map if present.
+     *
+     * @param key the key whose mapping is to be removed from the map
+     * @return the previous value associated with specified key, or
+     *     {@code null} if there was no entry for key.  (A {@code null}
+     *     return can also indicate that the map previously associated
+     *     {@code null} with the specified key.)
+     */
+    public V remove(Object key) {
+        if (!isValidKey(key))
+            return null;
+        int index = ((Enum<?>)key).ordinal();
+        Object oldValue = vals[index];
+        vals[index] = null;
+        if (oldValue != null)
+            size--;
+        return unmaskNull(oldValue);
+    }
+
+    private boolean removeMapping(Object key, Object value) {
+        if (!isValidKey(key))
+            return false;
+        int index = ((Enum<?>)key).ordinal();
+        if (maskNull(value).equals(vals[index])) {
+            vals[index] = null;
+            size--;
+            return true;
+        }
+        return false;
+    }
+
+    /**
+     * Returns true if key is of the proper type to be a key in this
+     * enum map.
+     */
+    private boolean isValidKey(Object key) {
+        if (key == null)
+            return false;
+
+        // Cheaper than instanceof Enum followed by getDeclaringClass
+        Class<?> keyClass = key.getClass();
+        return keyClass == keyType || keyClass.getSuperclass() == keyType;
+    }
+
+    // Bulk Operations
+
+    /**
+     * Copies all of the mappings from the specified map to this map.
+     * These mappings will replace any mappings that this map had for
+     * any of the keys currently in the specified map.
+     *
+     * @param m the mappings to be stored in this map
+     * @throws NullPointerException the specified map is null, or if
+     *     one or more keys in the specified map are null
+     */
+    public void putAll(Map<? extends K, ? extends V> m) {
+        if (m instanceof EnumMap) {
+            EnumMap<?, ?> em = (EnumMap<?, ?>)m;
+            if (em.keyType != keyType) {
+                if (em.isEmpty())
+                    return;
+                throw new ClassCastException(em.keyType + " != " + keyType);
+            }
+
+            for (int i = 0; i < keyUniverse.length; i++) {
+                Object emValue = em.vals[i];
+                if (emValue != null) {
+                    if (vals[i] == null)
+                        size++;
+                    vals[i] = emValue;
+                }
+            }
+        } else {
+            super.putAll(m);
+        }
+    }
+
+    /**
+     * Removes all mappings from this map.
+     */
+    public void clear() {
+        Arrays.fill(vals, null);
+        size = 0;
+    }
+
+    // Views
+
+    /**
+     * This field is initialized to contain an instance of the entry set
+     * view the first time this view is requested.  The view is stateless,
+     * so there's no reason to create more than one.
+     */
+    private transient Set<Map.Entry<K,V>> entrySet;
+
+    /**
+     * Returns a {@link Set} view of the keys contained in this map.
+     * The returned set obeys the general contract outlined in
+     * {@link Map#keySet()}.  The set's iterator will return the keys
+     * in their natural order (the order in which the enum constants
+     * are declared).
+     *
+     * @return a set view of the keys contained in this enum map
+     */
+    public Set<K> keySet() {
+        Set<K> ks = keySet;
+        if (ks == null) {
+            ks = new KeySet();
+            keySet = ks;
+        }
+        return ks;
+    }
+
+    private class KeySet extends AbstractSet<K> {
+        public Iterator<K> iterator() {
+            return new KeyIterator();
+        }
+        public int size() {
+            return size;
+        }
+        public boolean contains(Object o) {
+            return containsKey(o);
+        }
+        public boolean remove(Object o) {
+            int oldSize = size;
+            EnumMap.this.remove(o);
+            return size != oldSize;
+        }
+        public void clear() {
+            EnumMap.this.clear();
+        }
+    }
+
+    /**
+     * Returns a {@link Collection} view of the values contained in this map.
+     * The returned collection obeys the general contract outlined in
+     * {@link Map#values()}.  The collection's iterator will return the
+     * values in the order their corresponding keys appear in map,
+     * which is their natural order (the order in which the enum constants
+     * are declared).
+     *
+     * @return a collection view of the values contained in this map
+     */
+    public Collection<V> values() {
+        Collection<V> vs = values;
+        if (vs == null) {
+            vs = new Values();
+            values = vs;
+        }
+        return vs;
+    }
+
+    private class Values extends AbstractCollection<V> {
+        public Iterator<V> iterator() {
+            return new ValueIterator();
+        }
+        public int size() {
+            return size;
+        }
+        public boolean contains(Object o) {
+            return containsValue(o);
+        }
+        public boolean remove(Object o) {
+            o = maskNull(o);
+
+            for (int i = 0; i < vals.length; i++) {
+                if (o.equals(vals[i])) {
+                    vals[i] = null;
+                    size--;
+                    return true;
+                }
+            }
+            return false;
+        }
+        public void clear() {
+            EnumMap.this.clear();
+        }
+    }
+
+    /**
+     * Returns a {@link Set} view of the mappings contained in this map.
+     * The returned set obeys the general contract outlined in
+     * {@link Map#keySet()}.  The set's iterator will return the
+     * mappings in the order their keys appear in map, which is their
+     * natural order (the order in which the enum constants are declared).
+     *
+     * @return a set view of the mappings contained in this enum map
+     */
+    public Set<Map.Entry<K,V>> entrySet() {
+        Set<Map.Entry<K,V>> es = entrySet;
+        if (es != null)
+            return es;
+        else
+            return entrySet = new EntrySet();
+    }
+
+    private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
+        public Iterator<Map.Entry<K,V>> iterator() {
+            return new EntryIterator();
+        }
+
+        public boolean contains(Object o) {
+            if (!(o instanceof Map.Entry))
+                return false;
+            Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
+            return containsMapping(entry.getKey(), entry.getValue());
+        }
+        public boolean remove(Object o) {
+            if (!(o instanceof Map.Entry))
+                return false;
+            Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
+            return removeMapping(entry.getKey(), entry.getValue());
+        }
+        public int size() {
+            return size;
+        }
+        public void clear() {
+            EnumMap.this.clear();
+        }
+        public Object[] toArray() {
+            return fillEntryArray(new Object[size]);
+        }
+        @SuppressWarnings("unchecked")
+        public <T> T[] toArray(T[] a) {
+            int size = size();
+            if (a.length < size)
+                a = (T[])java.lang.reflect.Array
+                    .newInstance(a.getClass().getComponentType(), size);
+            if (a.length > size)
+                a[size] = null;
+            return (T[]) fillEntryArray(a);
+        }
+        private Object[] fillEntryArray(Object[] a) {
+            int j = 0;
+            for (int i = 0; i < vals.length; i++)
+                if (vals[i] != null)
+                    a[j++] = new AbstractMap.SimpleEntry<>(
+                        keyUniverse[i], unmaskNull(vals[i]));
+            return a;
+        }
+    }
+
+    private abstract class EnumMapIterator<T> implements Iterator<T> {
+        // Lower bound on index of next element to return
+        int index = 0;
+
+        // Index of last returned element, or -1 if none
+        int lastReturnedIndex = -1;
+
+        public boolean hasNext() {
+            while (index < vals.length && vals[index] == null)
+                index++;
+            return index != vals.length;
+        }
+
+        public void remove() {
+            checkLastReturnedIndex();
+
+            if (vals[lastReturnedIndex] != null) {
+                vals[lastReturnedIndex] = null;
+                size--;
+            }
+            lastReturnedIndex = -1;
+        }
+
+        private void checkLastReturnedIndex() {
+            if (lastReturnedIndex < 0)
+                throw new IllegalStateException();
+        }
+    }
+
+    private class KeyIterator extends EnumMapIterator<K> {
+        public K next() {
+            if (!hasNext())
+                throw new NoSuchElementException();
+            lastReturnedIndex = index++;
+            return keyUniverse[lastReturnedIndex];
+        }
+    }
+
+    private class ValueIterator extends EnumMapIterator<V> {
+        public V next() {
+            if (!hasNext())
+                throw new NoSuchElementException();
+            lastReturnedIndex = index++;
+            return unmaskNull(vals[lastReturnedIndex]);
+        }
+    }
+
+    private class EntryIterator extends EnumMapIterator<Map.Entry<K,V>> {
+        private Entry lastReturnedEntry;
+
+        public Map.Entry<K,V> next() {
+            if (!hasNext())
+                throw new NoSuchElementException();
+            lastReturnedEntry = new Entry(index++);
+            return lastReturnedEntry;
+        }
+
+        public void remove() {
+            lastReturnedIndex =
+                ((null == lastReturnedEntry) ? -1 : lastReturnedEntry.index);
+            super.remove();
+            lastReturnedEntry.index = lastReturnedIndex;
+            lastReturnedEntry = null;
+        }
+
+        private class Entry implements Map.Entry<K,V> {
+            private int index;
+
+            private Entry(int index) {
+                this.index = index;
+            }
+
+            public K getKey() {
+                checkIndexForEntryUse();
+                return keyUniverse[index];
+            }
+
+            public V getValue() {
+                checkIndexForEntryUse();
+                return unmaskNull(vals[index]);
+            }
+
+            public V setValue(V value) {
+                checkIndexForEntryUse();
+                V oldValue = unmaskNull(vals[index]);
+                vals[index] = maskNull(value);
+                return oldValue;
+            }
+
+            public boolean equals(Object o) {
+                if (index < 0)
+                    return o == this;
+
+                if (!(o instanceof Map.Entry))
+                    return false;
+
+                Map.Entry<?,?> e = (Map.Entry<?,?>)o;
+                V ourValue = unmaskNull(vals[index]);
+                Object hisValue = e.getValue();
+                return (e.getKey() == keyUniverse[index] &&
+                        (ourValue == hisValue ||
+                         (ourValue != null && ourValue.equals(hisValue))));
+            }
+
+            public int hashCode() {
+                if (index < 0)
+                    return super.hashCode();
+
+                return entryHashCode(index);
+            }
+
+            public String toString() {
+                if (index < 0)
+                    return super.toString();
+
+                return keyUniverse[index] + "="
+                    + unmaskNull(vals[index]);
+            }
+
+            private void checkIndexForEntryUse() {
+                if (index < 0)
+                    throw new IllegalStateException("Entry was removed");
+            }
+        }
+    }
+
+    // Comparison and hashing
+
+    /**
+     * Compares the specified object with this map for equality.  Returns
+     * {@code true} if the given object is also a map and the two maps
+     * represent the same mappings, as specified in the {@link
+     * Map#equals(Object)} contract.
+     *
+     * @param o the object to be compared for equality with this map
+     * @return {@code true} if the specified object is equal to this map
+     */
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o instanceof EnumMap)
+            return equals((EnumMap<?,?>)o);
+        if (!(o instanceof Map))
+            return false;
+
+        Map<?,?> m = (Map<?,?>)o;
+        if (size != m.size())
+            return false;
+
+        for (int i = 0; i < keyUniverse.length; i++) {
+            if (null != vals[i]) {
+                K key = keyUniverse[i];
+                V value = unmaskNull(vals[i]);
+                if (null == value) {
+                    if (!((null == m.get(key)) && m.containsKey(key)))
+                       return false;
+                } else {
+                   if (!value.equals(m.get(key)))
+                      return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
+    private boolean equals(EnumMap<?,?> em) {
+        if (em.size != size)
+            return false;
+
+        if (em.keyType != keyType)
+            return size == 0;
+
+        // Key types match, compare each value
+        for (int i = 0; i < keyUniverse.length; i++) {
+            Object ourValue =    vals[i];
+            Object hisValue = em.vals[i];
+            if (hisValue != ourValue &&
+                (hisValue == null || !hisValue.equals(ourValue)))
+                return false;
+        }
+        return true;
+    }
+
+    /**
+     * Returns the hash code value for this map.  The hash code of a map is
+     * defined to be the sum of the hash codes of each entry in the map.
+     */
+    public int hashCode() {
+        int h = 0;
+
+        for (int i = 0; i < keyUniverse.length; i++) {
+            if (null != vals[i]) {
+                h += entryHashCode(i);
+            }
+        }
+
+        return h;
+    }
+
+    private int entryHashCode(int index) {
+        return (keyUniverse[index].hashCode() ^ vals[index].hashCode());
+    }
+
+    /**
+     * Returns a shallow copy of this enum map. The values themselves
+     * are not cloned.
+     *
+     * @return a shallow copy of this enum map
+     */
+    @SuppressWarnings("unchecked")
+    public EnumMap<K, V> clone() {
+        EnumMap<K, V> result = null;
+        try {
+            result = (EnumMap<K, V>) super.clone();
+        } catch(CloneNotSupportedException e) {
+            throw new AssertionError();
+        }
+        result.vals = result.vals.clone();
+        result.entrySet = null;
+        return result;
+    }
+
+    /**
+     * Throws an exception if e is not of the correct type for this enum set.
+     */
+    private void typeCheck(K key) {
+        Class<?> keyClass = key.getClass();
+        if (keyClass != keyType && keyClass.getSuperclass() != keyType)
+            throw new ClassCastException(keyClass + " != " + keyType);
+    }
+
+    /**
+     * Returns all of the values comprising K.
+     * The result is uncloned, cached, and shared by all callers.
+     */
+    private static <K extends Enum<K>> K[] getKeyUniverse(Class<K> keyType) {
+        return SharedSecrets.getJavaLangAccess()
+                                        .getEnumConstantsShared(keyType);
+    }
+
+    private static final long serialVersionUID = 458661240069192865L;
+
+    /**
+     * Save the state of the {@code EnumMap} instance to a stream (i.e.,
+     * serialize it).
+     *
+     * @serialData The <i>size</i> of the enum map (the number of key-value
+     *             mappings) is emitted (int), followed by the key (Object)
+     *             and value (Object) for each key-value mapping represented
+     *             by the enum map.
+     */
+    private void writeObject(java.io.ObjectOutputStream s)
+        throws java.io.IOException
+    {
+        // Write out the key type and any hidden stuff
+        s.defaultWriteObject();
+
+        // Write out size (number of Mappings)
+        s.writeInt(size);
+
+        // Write out keys and values (alternating)
+        int entriesToBeWritten = size;
+        for (int i = 0; entriesToBeWritten > 0; i++) {
+            if (null != vals[i]) {
+                s.writeObject(keyUniverse[i]);
+                s.writeObject(unmaskNull(vals[i]));
+                entriesToBeWritten--;
+            }
+        }
+    }
+
+    /**
+     * Reconstitute the {@code EnumMap} instance from a stream (i.e.,
+     * deserialize it).
+     */
+    @SuppressWarnings("unchecked")
+    private void readObject(java.io.ObjectInputStream s)
+        throws java.io.IOException, ClassNotFoundException
+    {
+        // Read in the key type and any hidden stuff
+        s.defaultReadObject();
+
+        keyUniverse = getKeyUniverse(keyType);
+        vals = new Object[keyUniverse.length];
+
+        // Read in size (number of Mappings)
+        int size = s.readInt();
+
+        // Read the keys and values, and put the mappings in the HashMap
+        for (int i = 0; i < size; i++) {
+            K key = (K) s.readObject();
+            V value = (V) s.readObject();
+            put(key, value);
+        }
+    }
+}