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/* |
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* Copyright (c) 1997, 2007, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Sun designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Sun in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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|
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package java.util; |
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import java.util.Map.Entry; |
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|
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/** |
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* This class provides a skeletal implementation of the <tt>Map</tt> |
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* interface, to minimize the effort required to implement this interface. |
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* |
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* <p>To implement an unmodifiable map, the programmer needs only to extend this |
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* class and provide an implementation for the <tt>entrySet</tt> method, which |
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* returns a set-view of the map's mappings. Typically, the returned set |
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* will, in turn, be implemented atop <tt>AbstractSet</tt>. This set should |
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* not support the <tt>add</tt> or <tt>remove</tt> methods, and its iterator |
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* should not support the <tt>remove</tt> method. |
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* |
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* <p>To implement a modifiable map, the programmer must additionally override |
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* this class's <tt>put</tt> method (which otherwise throws an |
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* <tt>UnsupportedOperationException</tt>), and the iterator returned by |
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* <tt>entrySet().iterator()</tt> must additionally implement its |
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* <tt>remove</tt> method. |
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* |
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* <p>The programmer should generally provide a void (no argument) and map |
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* constructor, as per the recommendation in the <tt>Map</tt> interface |
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* specification. |
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* |
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* <p>The documentation for each non-abstract method in this class describes its |
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* implementation in detail. Each of these methods may be overridden if the |
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* map being implemented admits a more efficient implementation. |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @param <K> the type of keys maintained by this map |
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* @param <V> the type of mapped values |
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* |
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* @author Josh Bloch |
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* @author Neal Gafter |
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* @see Map |
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* @see Collection |
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* @since 1.2 |
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*/ |
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|
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public abstract class AbstractMap<K,V> implements Map<K,V> { |
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/** |
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* Sole constructor. (For invocation by subclass constructors, typically |
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* implicit.) |
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*/ |
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protected AbstractMap() { |
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} |
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|
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// Query Operations |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation returns <tt>entrySet().size()</tt>. |
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*/ |
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public int size() { |
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return entrySet().size(); |
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} |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation returns <tt>size() == 0</tt>. |
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*/ |
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public boolean isEmpty() { |
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return size() == 0; |
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} |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation iterates over <tt>entrySet()</tt> searching |
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* for an entry with the specified value. If such an entry is found, |
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* <tt>true</tt> is returned. If the iteration terminates without |
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* finding such an entry, <tt>false</tt> is returned. Note that this |
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* implementation requires linear time in the size of the map. |
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* |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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*/ |
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public boolean containsValue(Object value) { |
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Iterator<Entry<K,V>> i = entrySet().iterator(); |
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if (value==null) { |
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while (i.hasNext()) { |
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Entry<K,V> e = i.next(); |
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if (e.getValue()==null) |
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return true; |
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} |
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} else { |
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while (i.hasNext()) { |
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Entry<K,V> e = i.next(); |
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if (value.equals(e.getValue())) |
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return true; |
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} |
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} |
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return false; |
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} |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation iterates over <tt>entrySet()</tt> searching |
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* for an entry with the specified key. If such an entry is found, |
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* <tt>true</tt> is returned. If the iteration terminates without |
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* finding such an entry, <tt>false</tt> is returned. Note that this |
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* implementation requires linear time in the size of the map; many |
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* implementations will override this method. |
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* |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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*/ |
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public boolean containsKey(Object key) { |
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Iterator<Map.Entry<K,V>> i = entrySet().iterator(); |
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if (key==null) { |
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while (i.hasNext()) { |
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Entry<K,V> e = i.next(); |
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if (e.getKey()==null) |
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return true; |
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} |
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} else { |
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while (i.hasNext()) { |
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Entry<K,V> e = i.next(); |
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if (key.equals(e.getKey())) |
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return true; |
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} |
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} |
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return false; |
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} |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation iterates over <tt>entrySet()</tt> searching |
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* for an entry with the specified key. If such an entry is found, |
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* the entry's value is returned. If the iteration terminates without |
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* finding such an entry, <tt>null</tt> is returned. Note that this |
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* implementation requires linear time in the size of the map; many |
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* implementations will override this method. |
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* |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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*/ |
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public V get(Object key) { |
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Iterator<Entry<K,V>> i = entrySet().iterator(); |
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if (key==null) { |
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while (i.hasNext()) { |
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Entry<K,V> e = i.next(); |
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if (e.getKey()==null) |
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return e.getValue(); |
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} |
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} else { |
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while (i.hasNext()) { |
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Entry<K,V> e = i.next(); |
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if (key.equals(e.getKey())) |
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return e.getValue(); |
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} |
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} |
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return null; |
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} |
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|
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|
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// Modification Operations |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation always throws an |
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* <tt>UnsupportedOperationException</tt>. |
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* |
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* @throws UnsupportedOperationException {@inheritDoc} |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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* @throws IllegalArgumentException {@inheritDoc} |
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*/ |
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public V put(K key, V value) { |
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throw new UnsupportedOperationException(); |
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} |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation iterates over <tt>entrySet()</tt> searching for an |
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* entry with the specified key. If such an entry is found, its value is |
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* obtained with its <tt>getValue</tt> operation, the entry is removed |
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* from the collection (and the backing map) with the iterator's |
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* <tt>remove</tt> operation, and the saved value is returned. If the |
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* iteration terminates without finding such an entry, <tt>null</tt> is |
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* returned. Note that this implementation requires linear time in the |
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* size of the map; many implementations will override this method. |
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* |
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* <p>Note that this implementation throws an |
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* <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> |
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* iterator does not support the <tt>remove</tt> method and this map |
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* contains a mapping for the specified key. |
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* |
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* @throws UnsupportedOperationException {@inheritDoc} |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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*/ |
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public V remove(Object key) { |
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Iterator<Entry<K,V>> i = entrySet().iterator(); |
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Entry<K,V> correctEntry = null; |
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if (key==null) { |
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while (correctEntry==null && i.hasNext()) { |
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Entry<K,V> e = i.next(); |
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if (e.getKey()==null) |
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correctEntry = e; |
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} |
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} else { |
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while (correctEntry==null && i.hasNext()) { |
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Entry<K,V> e = i.next(); |
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if (key.equals(e.getKey())) |
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correctEntry = e; |
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} |
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} |
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|
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V oldValue = null; |
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if (correctEntry !=null) { |
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oldValue = correctEntry.getValue(); |
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i.remove(); |
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} |
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return oldValue; |
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} |
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|
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|
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// Bulk Operations |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation iterates over the specified map's |
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* <tt>entrySet()</tt> collection, and calls this map's <tt>put</tt> |
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* operation once for each entry returned by the iteration. |
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* |
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* <p>Note that this implementation throws an |
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* <tt>UnsupportedOperationException</tt> if this map does not support |
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* the <tt>put</tt> operation and the specified map is nonempty. |
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* |
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* @throws UnsupportedOperationException {@inheritDoc} |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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* @throws IllegalArgumentException {@inheritDoc} |
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*/ |
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public void putAll(Map<? extends K, ? extends V> m) { |
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for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) |
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put(e.getKey(), e.getValue()); |
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} |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation calls <tt>entrySet().clear()</tt>. |
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* |
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* <p>Note that this implementation throws an |
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* <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> |
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* does not support the <tt>clear</tt> operation. |
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* |
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* @throws UnsupportedOperationException {@inheritDoc} |
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*/ |
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public void clear() { |
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entrySet().clear(); |
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} |
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|
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|
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// Views |
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|
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/** |
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* Each of these fields are initialized to contain an instance of the |
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* appropriate view the first time this view is requested. The views are |
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* stateless, so there's no reason to create more than one of each. |
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*/ |
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transient volatile Set<K> keySet = null; |
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transient volatile Collection<V> values = null; |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation returns a set that subclasses {@link AbstractSet}. |
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* The subclass's iterator method returns a "wrapper object" over this |
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* map's <tt>entrySet()</tt> iterator. The <tt>size</tt> method |
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* delegates to this map's <tt>size</tt> method and the |
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* <tt>contains</tt> method delegates to this map's |
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* <tt>containsKey</tt> method. |
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* |
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* <p>The set is created the first time this method is called, |
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* and returned in response to all subsequent calls. No synchronization |
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* is performed, so there is a slight chance that multiple calls to this |
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* method will not all return the same set. |
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*/ |
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public Set<K> keySet() { |
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if (keySet == null) { |
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keySet = new AbstractSet<K>() { |
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public Iterator<K> iterator() { |
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return new Iterator<K>() { |
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private Iterator<Entry<K,V>> i = entrySet().iterator(); |
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|
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public boolean hasNext() { |
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return i.hasNext(); |
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} |
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|
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public K next() { |
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return i.next().getKey(); |
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} |
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|
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public void remove() { |
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i.remove(); |
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} |
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}; |
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} |
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|
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public int size() { |
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return AbstractMap.this.size(); |
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} |
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|
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public boolean isEmpty() { |
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return AbstractMap.this.isEmpty(); |
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} |
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|
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public void clear() { |
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AbstractMap.this.clear(); |
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} |
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|
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public boolean contains(Object k) { |
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return AbstractMap.this.containsKey(k); |
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} |
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}; |
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} |
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return keySet; |
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} |
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|
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation returns a collection that subclasses {@link |
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* AbstractCollection}. The subclass's iterator method returns a |
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* "wrapper object" over this map's <tt>entrySet()</tt> iterator. |
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* The <tt>size</tt> method delegates to this map's <tt>size</tt> |
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* method and the <tt>contains</tt> method delegates to this map's |
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* <tt>containsValue</tt> method. |
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* |
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* <p>The collection is created the first time this method is called, and |
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* returned in response to all subsequent calls. No synchronization is |
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* performed, so there is a slight chance that multiple calls to this |
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* method will not all return the same collection. |
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*/ |
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public Collection<V> values() { |
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if (values == null) { |
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values = new AbstractCollection<V>() { |
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public Iterator<V> iterator() { |
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return new Iterator<V>() { |
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private Iterator<Entry<K,V>> i = entrySet().iterator(); |
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|
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public boolean hasNext() { |
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return i.hasNext(); |
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} |
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|
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public V next() { |
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return i.next().getValue(); |
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} |
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|
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public void remove() { |
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i.remove(); |
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} |
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}; |
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} |
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|
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public int size() { |
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return AbstractMap.this.size(); |
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} |
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|
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public boolean isEmpty() { |
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return AbstractMap.this.isEmpty(); |
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} |
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|
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public void clear() { |
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AbstractMap.this.clear(); |
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} |
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|
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public boolean contains(Object v) { |
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return AbstractMap.this.containsValue(v); |
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} |
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}; |
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} |
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return values; |
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} |
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|
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public abstract Set<Entry<K,V>> entrySet(); |
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|
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|
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// Comparison and hashing |
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|
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/** |
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* Compares the specified object with this map for equality. Returns |
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* <tt>true</tt> if the given object is also a map and the two maps |
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* represent the same mappings. More formally, two maps <tt>m1</tt> and |
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* <tt>m2</tt> represent the same mappings if |
424 |
* <tt>m1.entrySet().equals(m2.entrySet())</tt>. This ensures that the |
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* <tt>equals</tt> method works properly across different implementations |
426 |
* of the <tt>Map</tt> interface. |
427 |
* |
428 |
* <p>This implementation first checks if the specified object is this map; |
429 |
* if so it returns <tt>true</tt>. Then, it checks if the specified |
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* object is a map whose size is identical to the size of this map; if |
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* not, it returns <tt>false</tt>. If so, it iterates over this map's |
432 |
* <tt>entrySet</tt> collection, and checks that the specified map |
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* contains each mapping that this map contains. If the specified map |
434 |
* fails to contain such a mapping, <tt>false</tt> is returned. If the |
435 |
* iteration completes, <tt>true</tt> is returned. |
436 |
* |
437 |
* @param o object to be compared for equality with this map |
438 |
* @return <tt>true</tt> if the specified object is equal to this map |
439 |
*/ |
440 |
public boolean equals(Object o) { |
441 |
if (o == this) |
442 |
return true; |
443 |
|
444 |
if (!(o instanceof Map)) |
445 |
return false; |
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Map<K,V> m = (Map<K,V>) o; |
447 |
if (m.size() != size()) |
448 |
return false; |
449 |
|
450 |
try { |
451 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
452 |
while (i.hasNext()) { |
453 |
Entry<K,V> e = i.next(); |
454 |
K key = e.getKey(); |
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V value = e.getValue(); |
456 |
if (value == null) { |
457 |
if (!(m.get(key)==null && m.containsKey(key))) |
458 |
return false; |
459 |
} else { |
460 |
if (!value.equals(m.get(key))) |
461 |
return false; |
462 |
} |
463 |
} |
464 |
} catch (ClassCastException unused) { |
465 |
return false; |
466 |
} catch (NullPointerException unused) { |
467 |
return false; |
468 |
} |
469 |
|
470 |
return true; |
471 |
} |
472 |
|
473 |
/** |
474 |
* Returns the hash code value for this map. The hash code of a map is |
475 |
* defined to be the sum of the hash codes of each entry in the map's |
476 |
* <tt>entrySet()</tt> view. This ensures that <tt>m1.equals(m2)</tt> |
477 |
* implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two maps |
478 |
* <tt>m1</tt> and <tt>m2</tt>, as required by the general contract of |
479 |
* {@link Object#hashCode}. |
480 |
* |
481 |
* <p>This implementation iterates over <tt>entrySet()</tt>, calling |
482 |
* {@link Map.Entry#hashCode hashCode()} on each element (entry) in the |
483 |
* set, and adding up the results. |
484 |
* |
485 |
* @return the hash code value for this map |
486 |
* @see Map.Entry#hashCode() |
487 |
* @see Object#equals(Object) |
488 |
* @see Set#equals(Object) |
489 |
*/ |
490 |
public int hashCode() { |
491 |
int h = 0; |
492 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
493 |
while (i.hasNext()) |
494 |
h += i.next().hashCode(); |
495 |
return h; |
496 |
} |
497 |
|
498 |
/** |
499 |
* Returns a string representation of this map. The string representation |
500 |
* consists of a list of key-value mappings in the order returned by the |
501 |
* map's <tt>entrySet</tt> view's iterator, enclosed in braces |
502 |
* (<tt>"{}"</tt>). Adjacent mappings are separated by the characters |
503 |
* <tt>", "</tt> (comma and space). Each key-value mapping is rendered as |
504 |
* the key followed by an equals sign (<tt>"="</tt>) followed by the |
505 |
* associated value. Keys and values are converted to strings as by |
506 |
* {@link String#valueOf(Object)}. |
507 |
* |
508 |
* @return a string representation of this map |
509 |
*/ |
510 |
public String toString() { |
511 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
512 |
if (! i.hasNext()) |
513 |
return "{}"; |
514 |
|
515 |
StringBuilder sb = new StringBuilder(); |
516 |
sb.append('{'); |
517 |
for (;;) { |
518 |
Entry<K,V> e = i.next(); |
519 |
K key = e.getKey(); |
520 |
V value = e.getValue(); |
521 |
sb.append(key == this ? "(this Map)" : key); |
522 |
sb.append('='); |
523 |
sb.append(value == this ? "(this Map)" : value); |
524 |
if (! i.hasNext()) |
525 |
return sb.append('}').toString(); |
526 |
sb.append(',').append(' '); |
527 |
} |
528 |
} |
529 |
|
530 |
/** |
531 |
* Returns a shallow copy of this <tt>AbstractMap</tt> instance: the keys |
532 |
* and values themselves are not cloned. |
533 |
* |
534 |
* @return a shallow copy of this map |
535 |
*/ |
536 |
protected Object clone() throws CloneNotSupportedException { |
537 |
AbstractMap<K,V> result = (AbstractMap<K,V>)super.clone(); |
538 |
result.keySet = null; |
539 |
result.values = null; |
540 |
return result; |
541 |
} |
542 |
|
543 |
/** |
544 |
* Utility method for SimpleEntry and SimpleImmutableEntry. |
545 |
* Test for equality, checking for nulls. |
546 |
*/ |
547 |
private static boolean eq(Object o1, Object o2) { |
548 |
return o1 == null ? o2 == null : o1.equals(o2); |
549 |
} |
550 |
|
551 |
// Implementation Note: SimpleEntry and SimpleImmutableEntry |
552 |
// are distinct unrelated classes, even though they share |
553 |
// some code. Since you can't add or subtract final-ness |
554 |
// of a field in a subclass, they can't share representations, |
555 |
// and the amount of duplicated code is too small to warrant |
556 |
// exposing a common abstract class. |
557 |
|
558 |
|
559 |
/** |
560 |
* An Entry maintaining a key and a value. The value may be |
561 |
* changed using the <tt>setValue</tt> method. This class |
562 |
* facilitates the process of building custom map |
563 |
* implementations. For example, it may be convenient to return |
564 |
* arrays of <tt>SimpleEntry</tt> instances in method |
565 |
* <tt>Map.entrySet().toArray</tt>. |
566 |
* |
567 |
* @since 1.6 |
568 |
*/ |
569 |
public static class SimpleEntry<K,V> |
570 |
implements Entry<K,V>, java.io.Serializable |
571 |
{ |
572 |
private static final long serialVersionUID = -8499721149061103585L; |
573 |
|
574 |
private final K key; |
575 |
private V value; |
576 |
|
577 |
/** |
578 |
* Creates an entry representing a mapping from the specified |
579 |
* key to the specified value. |
580 |
* |
581 |
* @param key the key represented by this entry |
582 |
* @param value the value represented by this entry |
583 |
*/ |
584 |
public SimpleEntry(K key, V value) { |
585 |
this.key = key; |
586 |
this.value = value; |
587 |
} |
588 |
|
589 |
/** |
590 |
* Creates an entry representing the same mapping as the |
591 |
* specified entry. |
592 |
* |
593 |
* @param entry the entry to copy |
594 |
*/ |
595 |
public SimpleEntry(Entry<? extends K, ? extends V> entry) { |
596 |
this.key = entry.getKey(); |
597 |
this.value = entry.getValue(); |
598 |
} |
599 |
|
600 |
/** |
601 |
* Returns the key corresponding to this entry. |
602 |
* |
603 |
* @return the key corresponding to this entry |
604 |
*/ |
605 |
public K getKey() { |
606 |
return key; |
607 |
} |
608 |
|
609 |
/** |
610 |
* Returns the value corresponding to this entry. |
611 |
* |
612 |
* @return the value corresponding to this entry |
613 |
*/ |
614 |
public V getValue() { |
615 |
return value; |
616 |
} |
617 |
|
618 |
/** |
619 |
* Replaces the value corresponding to this entry with the specified |
620 |
* value. |
621 |
* |
622 |
* @param value new value to be stored in this entry |
623 |
* @return the old value corresponding to the entry |
624 |
*/ |
625 |
public V setValue(V value) { |
626 |
V oldValue = this.value; |
627 |
this.value = value; |
628 |
return oldValue; |
629 |
} |
630 |
|
631 |
/** |
632 |
* Compares the specified object with this entry for equality. |
633 |
* Returns {@code true} if the given object is also a map entry and |
634 |
* the two entries represent the same mapping. More formally, two |
635 |
* entries {@code e1} and {@code e2} represent the same mapping |
636 |
* if<pre> |
637 |
* (e1.getKey()==null ? |
638 |
* e2.getKey()==null : |
639 |
* e1.getKey().equals(e2.getKey())) |
640 |
* && |
641 |
* (e1.getValue()==null ? |
642 |
* e2.getValue()==null : |
643 |
* e1.getValue().equals(e2.getValue()))</pre> |
644 |
* This ensures that the {@code equals} method works properly across |
645 |
* different implementations of the {@code Map.Entry} interface. |
646 |
* |
647 |
* @param o object to be compared for equality with this map entry |
648 |
* @return {@code true} if the specified object is equal to this map |
649 |
* entry |
650 |
* @see #hashCode |
651 |
*/ |
652 |
public boolean equals(Object o) { |
653 |
if (!(o instanceof Map.Entry)) |
654 |
return false; |
655 |
Map.Entry e = (Map.Entry)o; |
656 |
return eq(key, e.getKey()) && eq(value, e.getValue()); |
657 |
} |
658 |
|
659 |
/** |
660 |
* Returns the hash code value for this map entry. The hash code |
661 |
* of a map entry {@code e} is defined to be: <pre> |
662 |
* (e.getKey()==null ? 0 : e.getKey().hashCode()) ^ |
663 |
* (e.getValue()==null ? 0 : e.getValue().hashCode())</pre> |
664 |
* This ensures that {@code e1.equals(e2)} implies that |
665 |
* {@code e1.hashCode()==e2.hashCode()} for any two Entries |
666 |
* {@code e1} and {@code e2}, as required by the general |
667 |
* contract of {@link Object#hashCode}. |
668 |
* |
669 |
* @return the hash code value for this map entry |
670 |
* @see #equals |
671 |
*/ |
672 |
public int hashCode() { |
673 |
return (key == null ? 0 : key.hashCode()) ^ |
674 |
(value == null ? 0 : value.hashCode()); |
675 |
} |
676 |
|
677 |
/** |
678 |
* Returns a String representation of this map entry. This |
679 |
* implementation returns the string representation of this |
680 |
* entry's key followed by the equals character ("<tt>=</tt>") |
681 |
* followed by the string representation of this entry's value. |
682 |
* |
683 |
* @return a String representation of this map entry |
684 |
*/ |
685 |
public String toString() { |
686 |
return key + "=" + value; |
687 |
} |
688 |
|
689 |
} |
690 |
|
691 |
/** |
692 |
* An Entry maintaining an immutable key and value. This class |
693 |
* does not support method <tt>setValue</tt>. This class may be |
694 |
* convenient in methods that return thread-safe snapshots of |
695 |
* key-value mappings. |
696 |
* |
697 |
* @since 1.6 |
698 |
*/ |
699 |
public static class SimpleImmutableEntry<K,V> |
700 |
implements Entry<K,V>, java.io.Serializable |
701 |
{ |
702 |
private static final long serialVersionUID = 7138329143949025153L; |
703 |
|
704 |
private final K key; |
705 |
private final V value; |
706 |
|
707 |
/** |
708 |
* Creates an entry representing a mapping from the specified |
709 |
* key to the specified value. |
710 |
* |
711 |
* @param key the key represented by this entry |
712 |
* @param value the value represented by this entry |
713 |
*/ |
714 |
public SimpleImmutableEntry(K key, V value) { |
715 |
this.key = key; |
716 |
this.value = value; |
717 |
} |
718 |
|
719 |
/** |
720 |
* Creates an entry representing the same mapping as the |
721 |
* specified entry. |
722 |
* |
723 |
* @param entry the entry to copy |
724 |
*/ |
725 |
public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) { |
726 |
this.key = entry.getKey(); |
727 |
this.value = entry.getValue(); |
728 |
} |
729 |
|
730 |
/** |
731 |
* Returns the key corresponding to this entry. |
732 |
* |
733 |
* @return the key corresponding to this entry |
734 |
*/ |
735 |
public K getKey() { |
736 |
return key; |
737 |
} |
738 |
|
739 |
/** |
740 |
* Returns the value corresponding to this entry. |
741 |
* |
742 |
* @return the value corresponding to this entry |
743 |
*/ |
744 |
public V getValue() { |
745 |
return value; |
746 |
} |
747 |
|
748 |
/** |
749 |
* Replaces the value corresponding to this entry with the specified |
750 |
* value (optional operation). This implementation simply throws |
751 |
* <tt>UnsupportedOperationException</tt>, as this class implements |
752 |
* an <i>immutable</i> map entry. |
753 |
* |
754 |
* @param value new value to be stored in this entry |
755 |
* @return (Does not return) |
756 |
* @throws UnsupportedOperationException always |
757 |
*/ |
758 |
public V setValue(V value) { |
759 |
throw new UnsupportedOperationException(); |
760 |
} |
761 |
|
762 |
/** |
763 |
* Compares the specified object with this entry for equality. |
764 |
* Returns {@code true} if the given object is also a map entry and |
765 |
* the two entries represent the same mapping. More formally, two |
766 |
* entries {@code e1} and {@code e2} represent the same mapping |
767 |
* if<pre> |
768 |
* (e1.getKey()==null ? |
769 |
* e2.getKey()==null : |
770 |
* e1.getKey().equals(e2.getKey())) |
771 |
* && |
772 |
* (e1.getValue()==null ? |
773 |
* e2.getValue()==null : |
774 |
* e1.getValue().equals(e2.getValue()))</pre> |
775 |
* This ensures that the {@code equals} method works properly across |
776 |
* different implementations of the {@code Map.Entry} interface. |
777 |
* |
778 |
* @param o object to be compared for equality with this map entry |
779 |
* @return {@code true} if the specified object is equal to this map |
780 |
* entry |
781 |
* @see #hashCode |
782 |
*/ |
783 |
public boolean equals(Object o) { |
784 |
if (!(o instanceof Map.Entry)) |
785 |
return false; |
786 |
Map.Entry e = (Map.Entry)o; |
787 |
return eq(key, e.getKey()) && eq(value, e.getValue()); |
788 |
} |
789 |
|
790 |
/** |
791 |
* Returns the hash code value for this map entry. The hash code |
792 |
* of a map entry {@code e} is defined to be: <pre> |
793 |
* (e.getKey()==null ? 0 : e.getKey().hashCode()) ^ |
794 |
* (e.getValue()==null ? 0 : e.getValue().hashCode())</pre> |
795 |
* This ensures that {@code e1.equals(e2)} implies that |
796 |
* {@code e1.hashCode()==e2.hashCode()} for any two Entries |
797 |
* {@code e1} and {@code e2}, as required by the general |
798 |
* contract of {@link Object#hashCode}. |
799 |
* |
800 |
* @return the hash code value for this map entry |
801 |
* @see #equals |
802 |
*/ |
803 |
public int hashCode() { |
804 |
return (key == null ? 0 : key.hashCode()) ^ |
805 |
(value == null ? 0 : value.hashCode()); |
806 |
} |
807 |
|
808 |
/** |
809 |
* Returns a String representation of this map entry. This |
810 |
* implementation returns the string representation of this |
811 |
* entry's key followed by the equals character ("<tt>=</tt>") |
812 |
* followed by the string representation of this entry's value. |
813 |
* |
814 |
* @return a String representation of this map entry |
815 |
*/ |
816 |
public String toString() { |
817 |
return key + "=" + value; |
818 |
} |
819 |
|
820 |
} |
821 |
|
822 |
} |