--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/AbstractMap.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,822 @@
+/*
+ * Copyright 1997-2007 Sun Microsystems, Inc. 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. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package java.util;
+import java.util.Map.Entry;
+
+/**
+ * This class provides a skeletal implementation of the <tt>Map</tt>
+ * interface, to minimize the effort required to implement this interface.
+ *
+ * <p>To implement an unmodifiable map, the programmer needs only to extend this
+ * class and provide an implementation for the <tt>entrySet</tt> method, which
+ * returns a set-view of the map's mappings. Typically, the returned set
+ * will, in turn, be implemented atop <tt>AbstractSet</tt>. This set should
+ * not support the <tt>add</tt> or <tt>remove</tt> methods, and its iterator
+ * should not support the <tt>remove</tt> method.
+ *
+ * <p>To implement a modifiable map, the programmer must additionally override
+ * this class's <tt>put</tt> method (which otherwise throws an
+ * <tt>UnsupportedOperationException</tt>), and the iterator returned by
+ * <tt>entrySet().iterator()</tt> must additionally implement its
+ * <tt>remove</tt> method.
+ *
+ * <p>The programmer should generally provide a void (no argument) and map
+ * constructor, as per the recommendation in the <tt>Map</tt> interface
+ * specification.
+ *
+ * <p>The documentation for each non-abstract method in this class describes its
+ * implementation in detail. Each of these methods may be overridden if the
+ * map being implemented admits a more efficient implementation.
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ *
+ * @author Josh Bloch
+ * @author Neal Gafter
+ * @see Map
+ * @see Collection
+ * @since 1.2
+ */
+
+public abstract class AbstractMap<K,V> implements Map<K,V> {
+ /**
+ * Sole constructor. (For invocation by subclass constructors, typically
+ * implicit.)
+ */
+ protected AbstractMap() {
+ }
+
+ // Query Operations
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation returns <tt>entrySet().size()</tt>.
+ */
+ public int size() {
+ return entrySet().size();
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation returns <tt>size() == 0</tt>.
+ */
+ public boolean isEmpty() {
+ return size() == 0;
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation iterates over <tt>entrySet()</tt> searching
+ * for an entry with the specified value. If such an entry is found,
+ * <tt>true</tt> is returned. If the iteration terminates without
+ * finding such an entry, <tt>false</tt> is returned. Note that this
+ * implementation requires linear time in the size of the map.
+ *
+ * @throws ClassCastException {@inheritDoc}
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean containsValue(Object value) {
+ Iterator<Entry<K,V>> i = entrySet().iterator();
+ if (value==null) {
+ while (i.hasNext()) {
+ Entry<K,V> e = i.next();
+ if (e.getValue()==null)
+ return true;
+ }
+ } else {
+ while (i.hasNext()) {
+ Entry<K,V> e = i.next();
+ if (value.equals(e.getValue()))
+ return true;
+ }
+ }
+ return false;
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation iterates over <tt>entrySet()</tt> searching
+ * for an entry with the specified key. If such an entry is found,
+ * <tt>true</tt> is returned. If the iteration terminates without
+ * finding such an entry, <tt>false</tt> is returned. Note that this
+ * implementation requires linear time in the size of the map; many
+ * implementations will override this method.
+ *
+ * @throws ClassCastException {@inheritDoc}
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean containsKey(Object key) {
+ Iterator<Map.Entry<K,V>> i = entrySet().iterator();
+ if (key==null) {
+ while (i.hasNext()) {
+ Entry<K,V> e = i.next();
+ if (e.getKey()==null)
+ return true;
+ }
+ } else {
+ while (i.hasNext()) {
+ Entry<K,V> e = i.next();
+ if (key.equals(e.getKey()))
+ return true;
+ }
+ }
+ return false;
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation iterates over <tt>entrySet()</tt> searching
+ * for an entry with the specified key. If such an entry is found,
+ * the entry's value is returned. If the iteration terminates without
+ * finding such an entry, <tt>null</tt> is returned. Note that this
+ * implementation requires linear time in the size of the map; many
+ * implementations will override this method.
+ *
+ * @throws ClassCastException {@inheritDoc}
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public V get(Object key) {
+ Iterator<Entry<K,V>> i = entrySet().iterator();
+ if (key==null) {
+ while (i.hasNext()) {
+ Entry<K,V> e = i.next();
+ if (e.getKey()==null)
+ return e.getValue();
+ }
+ } else {
+ while (i.hasNext()) {
+ Entry<K,V> e = i.next();
+ if (key.equals(e.getKey()))
+ return e.getValue();
+ }
+ }
+ return null;
+ }
+
+
+ // Modification Operations
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation always throws an
+ * <tt>UnsupportedOperationException</tt>.
+ *
+ * @throws UnsupportedOperationException {@inheritDoc}
+ * @throws ClassCastException {@inheritDoc}
+ * @throws NullPointerException {@inheritDoc}
+ * @throws IllegalArgumentException {@inheritDoc}
+ */
+ public V put(K key, V value) {
+ throw new UnsupportedOperationException();
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation iterates over <tt>entrySet()</tt> searching for an
+ * entry with the specified key. If such an entry is found, its value is
+ * obtained with its <tt>getValue</tt> operation, the entry is removed
+ * from the collection (and the backing map) with the iterator's
+ * <tt>remove</tt> operation, and the saved value is returned. If the
+ * iteration terminates without finding such an entry, <tt>null</tt> is
+ * returned. Note that this implementation requires linear time in the
+ * size of the map; many implementations will override this method.
+ *
+ * <p>Note that this implementation throws an
+ * <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt>
+ * iterator does not support the <tt>remove</tt> method and this map
+ * contains a mapping for the specified key.
+ *
+ * @throws UnsupportedOperationException {@inheritDoc}
+ * @throws ClassCastException {@inheritDoc}
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public V remove(Object key) {
+ Iterator<Entry<K,V>> i = entrySet().iterator();
+ Entry<K,V> correctEntry = null;
+ if (key==null) {
+ while (correctEntry==null && i.hasNext()) {
+ Entry<K,V> e = i.next();
+ if (e.getKey()==null)
+ correctEntry = e;
+ }
+ } else {
+ while (correctEntry==null && i.hasNext()) {
+ Entry<K,V> e = i.next();
+ if (key.equals(e.getKey()))
+ correctEntry = e;
+ }
+ }
+
+ V oldValue = null;
+ if (correctEntry !=null) {
+ oldValue = correctEntry.getValue();
+ i.remove();
+ }
+ return oldValue;
+ }
+
+
+ // Bulk Operations
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation iterates over the specified map's
+ * <tt>entrySet()</tt> collection, and calls this map's <tt>put</tt>
+ * operation once for each entry returned by the iteration.
+ *
+ * <p>Note that this implementation throws an
+ * <tt>UnsupportedOperationException</tt> if this map does not support
+ * the <tt>put</tt> operation and the specified map is nonempty.
+ *
+ * @throws UnsupportedOperationException {@inheritDoc}
+ * @throws ClassCastException {@inheritDoc}
+ * @throws NullPointerException {@inheritDoc}
+ * @throws IllegalArgumentException {@inheritDoc}
+ */
+ public void putAll(Map<? extends K, ? extends V> m) {
+ for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
+ put(e.getKey(), e.getValue());
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation calls <tt>entrySet().clear()</tt>.
+ *
+ * <p>Note that this implementation throws an
+ * <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt>
+ * does not support the <tt>clear</tt> operation.
+ *
+ * @throws UnsupportedOperationException {@inheritDoc}
+ */
+ public void clear() {
+ entrySet().clear();
+ }
+
+
+ // Views
+
+ /**
+ * Each of these fields are initialized to contain an instance of the
+ * appropriate view the first time this view is requested. The views are
+ * stateless, so there's no reason to create more than one of each.
+ */
+ transient volatile Set<K> keySet = null;
+ transient volatile Collection<V> values = null;
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation returns a set that subclasses {@link AbstractSet}.
+ * The subclass's iterator method returns a "wrapper object" over this
+ * map's <tt>entrySet()</tt> iterator. The <tt>size</tt> method
+ * delegates to this map's <tt>size</tt> method and the
+ * <tt>contains</tt> method delegates to this map's
+ * <tt>containsKey</tt> method.
+ *
+ * <p>The set is created the first time this method is called,
+ * and returned in response to all subsequent calls. No synchronization
+ * is performed, so there is a slight chance that multiple calls to this
+ * method will not all return the same set.
+ */
+ public Set<K> keySet() {
+ if (keySet == null) {
+ keySet = new AbstractSet<K>() {
+ public Iterator<K> iterator() {
+ return new Iterator<K>() {
+ private Iterator<Entry<K,V>> i = entrySet().iterator();
+
+ public boolean hasNext() {
+ return i.hasNext();
+ }
+
+ public K next() {
+ return i.next().getKey();
+ }
+
+ public void remove() {
+ i.remove();
+ }
+ };
+ }
+
+ public int size() {
+ return AbstractMap.this.size();
+ }
+
+ public boolean isEmpty() {
+ return AbstractMap.this.isEmpty();
+ }
+
+ public void clear() {
+ AbstractMap.this.clear();
+ }
+
+ public boolean contains(Object k) {
+ return AbstractMap.this.containsKey(k);
+ }
+ };
+ }
+ return keySet;
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * <p>This implementation returns a collection that subclasses {@link
+ * AbstractCollection}. The subclass's iterator method returns a
+ * "wrapper object" over this map's <tt>entrySet()</tt> iterator.
+ * The <tt>size</tt> method delegates to this map's <tt>size</tt>
+ * method and the <tt>contains</tt> method delegates to this map's
+ * <tt>containsValue</tt> method.
+ *
+ * <p>The collection is created the first time this method is called, and
+ * returned in response to all subsequent calls. No synchronization is
+ * performed, so there is a slight chance that multiple calls to this
+ * method will not all return the same collection.
+ */
+ public Collection<V> values() {
+ if (values == null) {
+ values = new AbstractCollection<V>() {
+ public Iterator<V> iterator() {
+ return new Iterator<V>() {
+ private Iterator<Entry<K,V>> i = entrySet().iterator();
+
+ public boolean hasNext() {
+ return i.hasNext();
+ }
+
+ public V next() {
+ return i.next().getValue();
+ }
+
+ public void remove() {
+ i.remove();
+ }
+ };
+ }
+
+ public int size() {
+ return AbstractMap.this.size();
+ }
+
+ public boolean isEmpty() {
+ return AbstractMap.this.isEmpty();
+ }
+
+ public void clear() {
+ AbstractMap.this.clear();
+ }
+
+ public boolean contains(Object v) {
+ return AbstractMap.this.containsValue(v);
+ }
+ };
+ }
+ return values;
+ }
+
+ public abstract Set<Entry<K,V>> entrySet();
+
+
+ // Comparison and hashing
+
+ /**
+ * Compares the specified object with this map for equality. Returns
+ * <tt>true</tt> if the given object is also a map and the two maps
+ * represent the same mappings. More formally, two maps <tt>m1</tt> and
+ * <tt>m2</tt> represent the same mappings if
+ * <tt>m1.entrySet().equals(m2.entrySet())</tt>. This ensures that the
+ * <tt>equals</tt> method works properly across different implementations
+ * of the <tt>Map</tt> interface.
+ *
+ * <p>This implementation first checks if the specified object is this map;
+ * if so it returns <tt>true</tt>. Then, it checks if the specified
+ * object is a map whose size is identical to the size of this map; if
+ * not, it returns <tt>false</tt>. If so, it iterates over this map's
+ * <tt>entrySet</tt> collection, and checks that the specified map
+ * contains each mapping that this map contains. If the specified map
+ * fails to contain such a mapping, <tt>false</tt> is returned. If the
+ * iteration completes, <tt>true</tt> is returned.
+ *
+ * @param o object to be compared for equality with this map
+ * @return <tt>true</tt> if the specified object is equal to this map
+ */
+ public boolean equals(Object o) {
+ if (o == this)
+ return true;
+
+ if (!(o instanceof Map))
+ return false;
+ Map<K,V> m = (Map<K,V>) o;
+ if (m.size() != size())
+ return false;
+
+ try {
+ Iterator<Entry<K,V>> i = entrySet().iterator();
+ while (i.hasNext()) {
+ Entry<K,V> e = i.next();
+ K key = e.getKey();
+ V value = e.getValue();
+ if (value == null) {
+ if (!(m.get(key)==null && m.containsKey(key)))
+ return false;
+ } else {
+ if (!value.equals(m.get(key)))
+ return false;
+ }
+ }
+ } catch (ClassCastException unused) {
+ return false;
+ } catch (NullPointerException unused) {
+ 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's
+ * <tt>entrySet()</tt> view. This ensures that <tt>m1.equals(m2)</tt>
+ * implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two maps
+ * <tt>m1</tt> and <tt>m2</tt>, as required by the general contract of
+ * {@link Object#hashCode}.
+ *
+ * <p>This implementation iterates over <tt>entrySet()</tt>, calling
+ * {@link Map.Entry#hashCode hashCode()} on each element (entry) in the
+ * set, and adding up the results.
+ *
+ * @return the hash code value for this map
+ * @see Map.Entry#hashCode()
+ * @see Object#equals(Object)
+ * @see Set#equals(Object)
+ */
+ public int hashCode() {
+ int h = 0;
+ Iterator<Entry<K,V>> i = entrySet().iterator();
+ while (i.hasNext())
+ h += i.next().hashCode();
+ return h;
+ }
+
+ /**
+ * Returns a string representation of this map. The string representation
+ * consists of a list of key-value mappings in the order returned by the
+ * map's <tt>entrySet</tt> view's iterator, enclosed in braces
+ * (<tt>"{}"</tt>). Adjacent mappings are separated by the characters
+ * <tt>", "</tt> (comma and space). Each key-value mapping is rendered as
+ * the key followed by an equals sign (<tt>"="</tt>) followed by the
+ * associated value. Keys and values are converted to strings as by
+ * {@link String#valueOf(Object)}.
+ *
+ * @return a string representation of this map
+ */
+ public String toString() {
+ Iterator<Entry<K,V>> i = entrySet().iterator();
+ if (! i.hasNext())
+ return "{}";
+
+ StringBuilder sb = new StringBuilder();
+ sb.append('{');
+ for (;;) {
+ Entry<K,V> e = i.next();
+ K key = e.getKey();
+ V value = e.getValue();
+ sb.append(key == this ? "(this Map)" : key);
+ sb.append('=');
+ sb.append(value == this ? "(this Map)" : value);
+ if (! i.hasNext())
+ return sb.append('}').toString();
+ sb.append(", ");
+ }
+ }
+
+ /**
+ * Returns a shallow copy of this <tt>AbstractMap</tt> instance: the keys
+ * and values themselves are not cloned.
+ *
+ * @return a shallow copy of this map
+ */
+ protected Object clone() throws CloneNotSupportedException {
+ AbstractMap<K,V> result = (AbstractMap<K,V>)super.clone();
+ result.keySet = null;
+ result.values = null;
+ return result;
+ }
+
+ /**
+ * Utility method for SimpleEntry and SimpleImmutableEntry.
+ * Test for equality, checking for nulls.
+ */
+ private static boolean eq(Object o1, Object o2) {
+ return o1 == null ? o2 == null : o1.equals(o2);
+ }
+
+ // Implementation Note: SimpleEntry and SimpleImmutableEntry
+ // are distinct unrelated classes, even though they share
+ // some code. Since you can't add or subtract final-ness
+ // of a field in a subclass, they can't share representations,
+ // and the amount of duplicated code is too small to warrant
+ // exposing a common abstract class.
+
+
+ /**
+ * An Entry maintaining a key and a value. The value may be
+ * changed using the <tt>setValue</tt> method. This class
+ * facilitates the process of building custom map
+ * implementations. For example, it may be convenient to return
+ * arrays of <tt>SimpleEntry</tt> instances in method
+ * <tt>Map.entrySet().toArray</tt>.
+ *
+ * @since 1.6
+ */
+ public static class SimpleEntry<K,V>
+ implements Entry<K,V>, java.io.Serializable
+ {
+ private static final long serialVersionUID = -8499721149061103585L;
+
+ private final K key;
+ private V value;
+
+ /**
+ * Creates an entry representing a mapping from the specified
+ * key to the specified value.
+ *
+ * @param key the key represented by this entry
+ * @param value the value represented by this entry
+ */
+ public SimpleEntry(K key, V value) {
+ this.key = key;
+ this.value = value;
+ }
+
+ /**
+ * Creates an entry representing the same mapping as the
+ * specified entry.
+ *
+ * @param entry the entry to copy
+ */
+ public SimpleEntry(Entry<? extends K, ? extends V> entry) {
+ this.key = entry.getKey();
+ this.value = entry.getValue();
+ }
+
+ /**
+ * Returns the key corresponding to this entry.
+ *
+ * @return the key corresponding to this entry
+ */
+ public K getKey() {
+ return key;
+ }
+
+ /**
+ * Returns the value corresponding to this entry.
+ *
+ * @return the value corresponding to this entry
+ */
+ public V getValue() {
+ return value;
+ }
+
+ /**
+ * Replaces the value corresponding to this entry with the specified
+ * value.
+ *
+ * @param value new value to be stored in this entry
+ * @return the old value corresponding to the entry
+ */
+ public V setValue(V value) {
+ V oldValue = this.value;
+ this.value = value;
+ return oldValue;
+ }
+
+ /**
+ * Compares the specified object with this entry for equality.
+ * Returns {@code true} if the given object is also a map entry and
+ * the two entries represent the same mapping. More formally, two
+ * entries {@code e1} and {@code e2} represent the same mapping
+ * if<pre>
+ * (e1.getKey()==null ?
+ * e2.getKey()==null :
+ * e1.getKey().equals(e2.getKey()))
+ * &&
+ * (e1.getValue()==null ?
+ * e2.getValue()==null :
+ * e1.getValue().equals(e2.getValue()))</pre>
+ * This ensures that the {@code equals} method works properly across
+ * different implementations of the {@code Map.Entry} interface.
+ *
+ * @param o object to be compared for equality with this map entry
+ * @return {@code true} if the specified object is equal to this map
+ * entry
+ * @see #hashCode
+ */
+ public boolean equals(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Map.Entry e = (Map.Entry)o;
+ return eq(key, e.getKey()) && eq(value, e.getValue());
+ }
+
+ /**
+ * Returns the hash code value for this map entry. The hash code
+ * of a map entry {@code e} is defined to be: <pre>
+ * (e.getKey()==null ? 0 : e.getKey().hashCode()) ^
+ * (e.getValue()==null ? 0 : e.getValue().hashCode())</pre>
+ * This ensures that {@code e1.equals(e2)} implies that
+ * {@code e1.hashCode()==e2.hashCode()} for any two Entries
+ * {@code e1} and {@code e2}, as required by the general
+ * contract of {@link Object#hashCode}.
+ *
+ * @return the hash code value for this map entry
+ * @see #equals
+ */
+ public int hashCode() {
+ return (key == null ? 0 : key.hashCode()) ^
+ (value == null ? 0 : value.hashCode());
+ }
+
+ /**
+ * Returns a String representation of this map entry. This
+ * implementation returns the string representation of this
+ * entry's key followed by the equals character ("<tt>=</tt>")
+ * followed by the string representation of this entry's value.
+ *
+ * @return a String representation of this map entry
+ */
+ public String toString() {
+ return key + "=" + value;
+ }
+
+ }
+
+ /**
+ * An Entry maintaining an immutable key and value. This class
+ * does not support method <tt>setValue</tt>. This class may be
+ * convenient in methods that return thread-safe snapshots of
+ * key-value mappings.
+ *
+ * @since 1.6
+ */
+ public static class SimpleImmutableEntry<K,V>
+ implements Entry<K,V>, java.io.Serializable
+ {
+ private static final long serialVersionUID = 7138329143949025153L;
+
+ private final K key;
+ private final V value;
+
+ /**
+ * Creates an entry representing a mapping from the specified
+ * key to the specified value.
+ *
+ * @param key the key represented by this entry
+ * @param value the value represented by this entry
+ */
+ public SimpleImmutableEntry(K key, V value) {
+ this.key = key;
+ this.value = value;
+ }
+
+ /**
+ * Creates an entry representing the same mapping as the
+ * specified entry.
+ *
+ * @param entry the entry to copy
+ */
+ public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) {
+ this.key = entry.getKey();
+ this.value = entry.getValue();
+ }
+
+ /**
+ * Returns the key corresponding to this entry.
+ *
+ * @return the key corresponding to this entry
+ */
+ public K getKey() {
+ return key;
+ }
+
+ /**
+ * Returns the value corresponding to this entry.
+ *
+ * @return the value corresponding to this entry
+ */
+ public V getValue() {
+ return value;
+ }
+
+ /**
+ * Replaces the value corresponding to this entry with the specified
+ * value (optional operation). This implementation simply throws
+ * <tt>UnsupportedOperationException</tt>, as this class implements
+ * an <i>immutable</i> map entry.
+ *
+ * @param value new value to be stored in this entry
+ * @return (Does not return)
+ * @throws UnsupportedOperationException always
+ */
+ public V setValue(V value) {
+ throw new UnsupportedOperationException();
+ }
+
+ /**
+ * Compares the specified object with this entry for equality.
+ * Returns {@code true} if the given object is also a map entry and
+ * the two entries represent the same mapping. More formally, two
+ * entries {@code e1} and {@code e2} represent the same mapping
+ * if<pre>
+ * (e1.getKey()==null ?
+ * e2.getKey()==null :
+ * e1.getKey().equals(e2.getKey()))
+ * &&
+ * (e1.getValue()==null ?
+ * e2.getValue()==null :
+ * e1.getValue().equals(e2.getValue()))</pre>
+ * This ensures that the {@code equals} method works properly across
+ * different implementations of the {@code Map.Entry} interface.
+ *
+ * @param o object to be compared for equality with this map entry
+ * @return {@code true} if the specified object is equal to this map
+ * entry
+ * @see #hashCode
+ */
+ public boolean equals(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Map.Entry e = (Map.Entry)o;
+ return eq(key, e.getKey()) && eq(value, e.getValue());
+ }
+
+ /**
+ * Returns the hash code value for this map entry. The hash code
+ * of a map entry {@code e} is defined to be: <pre>
+ * (e.getKey()==null ? 0 : e.getKey().hashCode()) ^
+ * (e.getValue()==null ? 0 : e.getValue().hashCode())</pre>
+ * This ensures that {@code e1.equals(e2)} implies that
+ * {@code e1.hashCode()==e2.hashCode()} for any two Entries
+ * {@code e1} and {@code e2}, as required by the general
+ * contract of {@link Object#hashCode}.
+ *
+ * @return the hash code value for this map entry
+ * @see #equals
+ */
+ public int hashCode() {
+ return (key == null ? 0 : key.hashCode()) ^
+ (value == null ? 0 : value.hashCode());
+ }
+
+ /**
+ * Returns a String representation of this map entry. This
+ * implementation returns the string representation of this
+ * entry's key followed by the equals character ("<tt>=</tt>")
+ * followed by the string representation of this entry's value.
+ *
+ * @return a String representation of this map entry
+ */
+ public String toString() {
+ return key + "=" + value;
+ }
+
+ }
+
+}