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/* |
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* %W% %E% |
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* |
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* Copyright 2005 Sun Microsystems, Inc. All rights reserved. |
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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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|
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package java.util; |
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import java.util.*; // for javadoc (till 6280605 is fixed) |
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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 methods 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}/../guide/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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* @version %I%, %G% |
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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 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 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 |
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* <tt>m1.entrySet().equals(m2.entrySet())</tt>. This ensures that the |
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* <tt>equals</tt> method works properly across different implementations |
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* of the <tt>Map</tt> interface. |
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* |
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* <p>This implementation first checks if the specified object is this map; |
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* 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 |
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* <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 |
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* fails to contain such a mapping, <tt>false</tt> is returned. If the |
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* iteration completes, <tt>true</tt> is returned. |
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* |
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* @param o object to be compared for equality with this map |
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* @return <tt>true</tt> if the specified object is equal to this map |
407 |
*/ |
408 |
public boolean equals(Object o) { |
409 |
if (o == this) |
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return true; |
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|
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if (!(o instanceof Map)) |
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return false; |
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Map<K,V> m = (Map<K,V>) o; |
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if (m.size() != size()) |
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return false; |
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|
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try { |
419 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
420 |
while (i.hasNext()) { |
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Entry<K,V> e = i.next(); |
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K key = e.getKey(); |
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V value = e.getValue(); |
424 |
if (value == null) { |
425 |
if (!(m.get(key)==null && m.containsKey(key))) |
426 |
return false; |
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} else { |
428 |
if (!value.equals(m.get(key))) |
429 |
return false; |
430 |
} |
431 |
} |
432 |
} catch (ClassCastException unused) { |
433 |
return false; |
434 |
} catch (NullPointerException unused) { |
435 |
return false; |
436 |
} |
437 |
|
438 |
return true; |
439 |
} |
440 |
|
441 |
/** |
442 |
* Returns the hash code value for this map. The hash code of a map is |
443 |
* defined to be the sum of the hash codes of each entry in the map's |
444 |
* <tt>entrySet()</tt> view. This ensures that <tt>m1.equals(m2)</tt> |
445 |
* implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two maps |
446 |
* <tt>m1</tt> and <tt>m2</tt>, as required by the general contract of |
447 |
* {@link Object#hashCode}. |
448 |
* |
449 |
* <p>This implementation iterates over <tt>entrySet()</tt>, calling |
450 |
* {@link Map.Entry#hashCode hashCode()} on each element (entry) in the |
451 |
* set, and adding up the results. |
452 |
* |
453 |
* @return the hash code value for this map |
454 |
* @see Map.Entry#hashCode() |
455 |
* @see Object#equals(Object) |
456 |
* @see Set#equals(Object) |
457 |
*/ |
458 |
public int hashCode() { |
459 |
int h = 0; |
460 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
461 |
while (i.hasNext()) |
462 |
h += i.next().hashCode(); |
463 |
return h; |
464 |
} |
465 |
|
466 |
/** |
467 |
* Returns a string representation of this map. The string representation |
468 |
* consists of a list of key-value mappings in the order returned by the |
469 |
* map's <tt>entrySet</tt> view's iterator, enclosed in braces |
470 |
* (<tt>"{}"</tt>). Adjacent mappings are separated by the characters |
471 |
* <tt>", "</tt> (comma and space). Each key-value mapping is rendered as |
472 |
* the key followed by an equals sign (<tt>"="</tt>) followed by the |
473 |
* associated value. Keys and values are converted to strings as by |
474 |
* {@link String#valueOf(Object)}. |
475 |
* |
476 |
* @return a string representation of this map |
477 |
*/ |
478 |
public String toString() { |
479 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
480 |
if (! i.hasNext()) |
481 |
return "{}"; |
482 |
|
483 |
StringBuilder sb = new StringBuilder(); |
484 |
sb.append('{'); |
485 |
for (;;) { |
486 |
Entry<K,V> e = i.next(); |
487 |
K key = e.getKey(); |
488 |
V value = e.getValue(); |
489 |
sb.append(key == this ? "(this Map)" : key); |
490 |
sb.append('='); |
491 |
sb.append(value == this ? "(this Map)" : value); |
492 |
if (! i.hasNext()) |
493 |
return sb.append('}').toString(); |
494 |
sb.append(", "); |
495 |
} |
496 |
} |
497 |
|
498 |
/** |
499 |
* Returns a shallow copy of this <tt>AbstractMap</tt> instance: the keys |
500 |
* and values themselves are not cloned. |
501 |
* |
502 |
* @return a shallow copy of this map |
503 |
*/ |
504 |
protected Object clone() throws CloneNotSupportedException { |
505 |
AbstractMap<K,V> result = (AbstractMap<K,V>)super.clone(); |
506 |
result.keySet = null; |
507 |
result.values = null; |
508 |
return result; |
509 |
} |
510 |
|
511 |
/** |
512 |
* Utility method for SimpleEntry and SimpleImmutableEntry. |
513 |
* Test for equality, checking for nulls. |
514 |
*/ |
515 |
private static boolean eq(Object o1, Object o2) { |
516 |
return o1 == null ? o2 == null : o1.equals(o2); |
517 |
} |
518 |
|
519 |
// Implementation Note: SimpleEntry and SimpleImmutableEntry |
520 |
// are distinct unrelated classes, even though they share |
521 |
// some code. Since you can't add or subtract final-ness |
522 |
// of a field in a subclass, they can't share representations, |
523 |
// and the amount of duplicated code is too small to warrant |
524 |
// exposing a common abstract class. |
525 |
|
526 |
|
527 |
/** |
528 |
* An Entry maintaining a key and a value. The value may be |
529 |
* changed using the <tt>setValue</tt> method. This class |
530 |
* facilitates the process of building custom map |
531 |
* implementations. For example, it may be convenient to return |
532 |
* arrays of <tt>SimpleEntry</tt> instances in method |
533 |
* <tt>Map.entrySet().toArray</tt>. |
534 |
* |
535 |
* @since 1.6 |
536 |
*/ |
537 |
public static class SimpleEntry<K,V> |
538 |
implements Entry<K,V>, java.io.Serializable |
539 |
{ |
540 |
private static final long serialVersionUID = -8499721149061103585L; |
541 |
|
542 |
private final K key; |
543 |
private V value; |
544 |
|
545 |
/** |
546 |
* Creates an entry representing a mapping from the specified |
547 |
* key to the specified value. |
548 |
* |
549 |
* @param key the key represented by this entry |
550 |
* @param value the value represented by this entry |
551 |
*/ |
552 |
public SimpleEntry(K key, V value) { |
553 |
this.key = key; |
554 |
this.value = value; |
555 |
} |
556 |
|
557 |
/** |
558 |
* Creates an entry representing the same mapping as the |
559 |
* specified entry. |
560 |
* |
561 |
* @param entry the entry to copy |
562 |
*/ |
563 |
public SimpleEntry(Entry<? extends K, ? extends V> entry) { |
564 |
this.key = entry.getKey(); |
565 |
this.value = entry.getValue(); |
566 |
} |
567 |
|
568 |
/** |
569 |
* Returns the key corresponding to this entry. |
570 |
* |
571 |
* @return the key corresponding to this entry |
572 |
*/ |
573 |
public K getKey() { |
574 |
return key; |
575 |
} |
576 |
|
577 |
/** |
578 |
* Returns the value corresponding to this entry. |
579 |
* |
580 |
* @return the value corresponding to this entry |
581 |
*/ |
582 |
public V getValue() { |
583 |
return value; |
584 |
} |
585 |
|
586 |
/** |
587 |
* Replaces the value corresponding to this entry with the specified |
588 |
* value. |
589 |
* |
590 |
* @param value new value to be stored in this entry |
591 |
* @return the old value corresponding to the entry |
592 |
*/ |
593 |
public V setValue(V value) { |
594 |
V oldValue = this.value; |
595 |
this.value = value; |
596 |
return oldValue; |
597 |
} |
598 |
|
599 |
/** |
600 |
* Compares the specified object with this entry for equality. |
601 |
* Returns {@code true} if the given object is also a map entry and |
602 |
* the two entries represent the same mapping. More formally, two |
603 |
* entries {@code e1} and {@code e2} represent the same mapping |
604 |
* if<pre> |
605 |
* (e1.getKey()==null ? |
606 |
* e2.getKey()==null : |
607 |
* e1.getKey().equals(e2.getKey())) |
608 |
* && |
609 |
* (e1.getValue()==null ? |
610 |
* e2.getValue()==null : |
611 |
* e1.getValue().equals(e2.getValue()))</pre> |
612 |
* This ensures that the {@code equals} method works properly across |
613 |
* different implementations of the {@code Map.Entry} interface. |
614 |
* |
615 |
* @param o object to be compared for equality with this map entry |
616 |
* @return {@code true} if the specified object is equal to this map |
617 |
* entry |
618 |
* @see #hashCode |
619 |
*/ |
620 |
public boolean equals(Object o) { |
621 |
if (!(o instanceof Map.Entry)) |
622 |
return false; |
623 |
Map.Entry e = (Map.Entry)o; |
624 |
return eq(key, e.getKey()) && eq(value, e.getValue()); |
625 |
} |
626 |
|
627 |
/** |
628 |
* Returns the hash code value for this map entry. The hash code |
629 |
* of a map entry {@code e} is defined to be: <pre> |
630 |
* (e.getKey()==null ? 0 : e.getKey().hashCode()) ^ |
631 |
* (e.getValue()==null ? 0 : e.getValue().hashCode())</pre> |
632 |
* This ensures that {@code e1.equals(e2)} implies that |
633 |
* {@code e1.hashCode()==e2.hashCode()} for any two Entries |
634 |
* {@code e1} and {@code e2}, as required by the general |
635 |
* contract of {@link Object#hashCode}. |
636 |
* |
637 |
* @return the hash code value for this map entry |
638 |
* @see #equals |
639 |
*/ |
640 |
public int hashCode() { |
641 |
return (key == null ? 0 : key.hashCode()) ^ |
642 |
(value == null ? 0 : value.hashCode()); |
643 |
} |
644 |
|
645 |
/** |
646 |
* Returns a String representation of this map entry. This |
647 |
* implementation returns the string representation of this |
648 |
* entry's key followed by the equals character ("<tt>=</tt>") |
649 |
* followed by the string representation of this entry's value. |
650 |
* |
651 |
* @return a String representation of this map entry |
652 |
*/ |
653 |
public String toString() { |
654 |
return key + "=" + value; |
655 |
} |
656 |
|
657 |
} |
658 |
|
659 |
/** |
660 |
* An Entry maintaining an immutable key and value. This class |
661 |
* does not support method <tt>setValue</tt>. This class may be |
662 |
* convenient in methods that return thread-safe snapshots of |
663 |
* key-value mappings. |
664 |
* |
665 |
* @since 1.6 |
666 |
*/ |
667 |
public static class SimpleImmutableEntry<K,V> |
668 |
implements Entry<K,V>, java.io.Serializable |
669 |
{ |
670 |
private static final long serialVersionUID = 7138329143949025153L; |
671 |
|
672 |
private final K key; |
673 |
private final V value; |
674 |
|
675 |
/** |
676 |
* Creates an entry representing a mapping from the specified |
677 |
* key to the specified value. |
678 |
* |
679 |
* @param key the key represented by this entry |
680 |
* @param value the value represented by this entry |
681 |
*/ |
682 |
public SimpleImmutableEntry(K key, V value) { |
683 |
this.key = key; |
684 |
this.value = value; |
685 |
} |
686 |
|
687 |
/** |
688 |
* Creates an entry representing the same mapping as the |
689 |
* specified entry. |
690 |
* |
691 |
* @param entry the entry to copy |
692 |
*/ |
693 |
public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) { |
694 |
this.key = entry.getKey(); |
695 |
this.value = entry.getValue(); |
696 |
} |
697 |
|
698 |
/** |
699 |
* Returns the key corresponding to this entry. |
700 |
* |
701 |
* @return the key corresponding to this entry |
702 |
*/ |
703 |
public K getKey() { |
704 |
return key; |
705 |
} |
706 |
|
707 |
/** |
708 |
* Returns the value corresponding to this entry. |
709 |
* |
710 |
* @return the value corresponding to this entry |
711 |
*/ |
712 |
public V getValue() { |
713 |
return value; |
714 |
} |
715 |
|
716 |
/** |
717 |
* Replaces the value corresponding to this entry with the specified |
718 |
* value (optional operation). This implementation simply throws |
719 |
* <tt>UnsupportedOperationException</tt>, as this class implements |
720 |
* an <i>immutable</i> map entry. |
721 |
* |
722 |
* @param value new value to be stored in this entry |
723 |
* @return (Does not return) |
724 |
* @throws UnsupportedOperationException always |
725 |
*/ |
726 |
public V setValue(V value) { |
727 |
throw new UnsupportedOperationException(); |
728 |
} |
729 |
|
730 |
/** |
731 |
* Compares the specified object with this entry for equality. |
732 |
* Returns {@code true} if the given object is also a map entry and |
733 |
* the two entries represent the same mapping. More formally, two |
734 |
* entries {@code e1} and {@code e2} represent the same mapping |
735 |
* if<pre> |
736 |
* (e1.getKey()==null ? |
737 |
* e2.getKey()==null : |
738 |
* e1.getKey().equals(e2.getKey())) |
739 |
* && |
740 |
* (e1.getValue()==null ? |
741 |
* e2.getValue()==null : |
742 |
* e1.getValue().equals(e2.getValue()))</pre> |
743 |
* This ensures that the {@code equals} method works properly across |
744 |
* different implementations of the {@code Map.Entry} interface. |
745 |
* |
746 |
* @param o object to be compared for equality with this map entry |
747 |
* @return {@code true} if the specified object is equal to this map |
748 |
* entry |
749 |
* @see #hashCode |
750 |
*/ |
751 |
public boolean equals(Object o) { |
752 |
if (!(o instanceof Map.Entry)) |
753 |
return false; |
754 |
Map.Entry e = (Map.Entry)o; |
755 |
return eq(key, e.getKey()) && eq(value, e.getValue()); |
756 |
} |
757 |
|
758 |
/** |
759 |
* Returns the hash code value for this map entry. The hash code |
760 |
* of a map entry {@code e} is defined to be: <pre> |
761 |
* (e.getKey()==null ? 0 : e.getKey().hashCode()) ^ |
762 |
* (e.getValue()==null ? 0 : e.getValue().hashCode())</pre> |
763 |
* This ensures that {@code e1.equals(e2)} implies that |
764 |
* {@code e1.hashCode()==e2.hashCode()} for any two Entries |
765 |
* {@code e1} and {@code e2}, as required by the general |
766 |
* contract of {@link Object#hashCode}. |
767 |
* |
768 |
* @return the hash code value for this map entry |
769 |
* @see #equals |
770 |
*/ |
771 |
public int hashCode() { |
772 |
return (key == null ? 0 : key.hashCode()) ^ |
773 |
(value == null ? 0 : value.hashCode()); |
774 |
} |
775 |
|
776 |
/** |
777 |
* Returns a String representation of this map entry. This |
778 |
* implementation returns the string representation of this |
779 |
* entry's key followed by the equals character ("<tt>=</tt>") |
780 |
* followed by the string representation of this entry's value. |
781 |
* |
782 |
* @return a String representation of this map entry |
783 |
*/ |
784 |
public String toString() { |
785 |
return key + "=" + value; |
786 |
} |
787 |
|
788 |
} |
789 |
|
790 |
} |