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/* |
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* %W% %E% |
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* |
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* Copyright 2004 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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package java.util; |
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import java.util.Map.Entry; |
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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. <p> |
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* |
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* 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.<p> |
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* |
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* 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.<p> |
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* |
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* 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.<p> |
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* |
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* 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.<p> |
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* |
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* 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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* @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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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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// Query Operations |
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/** |
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* Returns the number of key-value mappings in this map. If the map |
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* contains more than <tt>Integer.MAX_VALUE</tt> elements, returns |
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* <tt>Integer.MAX_VALUE</tt>.<p> |
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* |
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* This implementation returns <tt>entrySet().size()</tt>. |
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* |
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* @return the number of key-value mappings in this map. |
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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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* Returns <tt>true</tt> if this map contains no key-value mappings. <p> |
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* |
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* This implementation returns <tt>size() == 0</tt>. |
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* |
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* @return <tt>true</tt> if this map contains no key-value mappings. |
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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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* Returns <tt>true</tt> if this map maps one or more keys to this value. |
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* More formally, returns <tt>true</tt> if and only if this map contains |
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* at least one mapping to a value <tt>v</tt> such that <tt>(value==null ? |
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* v==null : value.equals(v))</tt>. This operation will probably require |
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* time linear in the map size for most implementations of map.<p> |
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* |
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* This implementation iterates over entrySet() searching for an entry |
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* with the specified value. If such an entry is found, <tt>true</tt> is |
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* returned. If the iteration terminates without finding such an entry, |
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* <tt>false</tt> is returned. Note that this implementation requires |
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* linear time in the size of the map. |
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* |
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* @param value value whose presence in this map is to be tested. |
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* |
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* @return <tt>true</tt> if this map maps one or more keys to this value. |
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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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* Returns <tt>true</tt> if this map contains a mapping for the specified |
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* key. <p> |
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* |
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* 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, <tt>true</tt> |
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* is returned. If the iteration terminates without finding such an |
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* entry, <tt>false</tt> is returned. Note that this implementation |
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* requires linear time in the size of the map; many implementations will |
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* override this method. |
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* |
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* @param key key whose presence in this map is to be tested. |
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* @return <tt>true</tt> if this map contains a mapping for the specified |
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* key. |
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* |
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* @throws NullPointerException if the key is <tt>null</tt> and this map |
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* does not permit <tt>null</tt> keys. |
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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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* Returns the value to which this map maps the specified key. Returns |
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* <tt>null</tt> if the map contains no mapping for this key. A return |
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* value of <tt>null</tt> does not <i>necessarily</i> indicate that the |
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* map contains no mapping for the key; it's also possible that the map |
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* explicitly maps the key to <tt>null</tt>. The containsKey operation |
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* may be used to distinguish these two cases. <p> |
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* |
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* 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, the entry's |
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* value is returned. If the iteration terminates without finding such an |
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* entry, <tt>null</tt> is returned. Note that this implementation |
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* requires linear time in the size of the map; many implementations will |
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* override this method. |
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* |
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* @param key key whose associated value is to be returned. |
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* @return the value to which this map maps the specified key. |
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* |
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* @throws NullPointerException if the key is <tt>null</tt> and this map |
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* does not permit <tt>null</tt> keys. |
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* |
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* @see #containsKey(Object) |
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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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// Modification Operations |
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/** |
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* Associates the specified value with the specified key in this map |
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* (optional operation). If the map previously contained a mapping for |
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* this key, the old value is replaced.<p> |
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* |
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* This implementation always throws an |
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* <tt>UnsupportedOperationException</tt>. |
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* |
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* @param key key with which the specified value is to be associated. |
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* @param value value to be associated with the specified key. |
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* |
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* @return the previous value associated with specified key, or <tt>null</tt> |
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* if there was no mapping for key. (A <tt>null</tt> return can |
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* also indicate that the map previously associated <tt>null</tt> |
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* with the specified key, if the implementation supports |
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* <tt>null</tt> values.) |
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* |
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* @throws UnsupportedOperationException if the <tt>put</tt> operation is |
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* not supported by this map. |
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* |
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* @throws ClassCastException if the class of the specified key or value |
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* prevents it from being stored in this map. |
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* |
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* @throws IllegalArgumentException if some aspect of this key or value * |
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* prevents it from being stored in this map. |
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* |
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* @throws NullPointerException if this map does not permit <tt>null</tt> |
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* keys or values, and the specified key or value is |
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* <tt>null</tt>. |
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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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* Removes the mapping for this key from this map if present (optional |
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* operation). <p> |
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* |
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* 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.<p> |
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* |
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* Note that this implementation throws an |
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* <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> iterator |
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* does not support the <tt>remove</tt> method and this map contains a |
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* mapping for the specified key. |
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* |
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* @param key key whose mapping is to be removed from the map. |
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dl |
1.5 |
* @return the previous value associated with specified key, or <tt>null</tt> |
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dl |
1.1 |
* if there was no entry for key. (A <tt>null</tt> return can |
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* also indicate that the map previously associated <tt>null</tt> |
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* with the specified key, if the implementation supports |
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* <tt>null</tt> values.) |
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* @throws UnsupportedOperationException if the <tt>remove</tt> operation |
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* is not supported by this map. |
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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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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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// Bulk Operations |
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/** |
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* Copies all of the mappings from the specified map to this map |
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* (optional operation). These mappings will replace any mappings that |
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* this map had for any of the keys currently in the specified map.<p> |
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* |
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* 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.<p> |
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* |
295 |
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* 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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* @param t mappings to be stored in this map. |
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* |
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* @throws UnsupportedOperationException if the <tt>putAll</tt> operation |
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* is not supported by this map. |
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* |
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* @throws ClassCastException if the class of a key or value in the |
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* specified map prevents it from being stored in this map. |
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* |
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* @throws IllegalArgumentException if some aspect of a key or value in |
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* the specified map prevents it from being stored in this map. |
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* @throws NullPointerException if the specified map is <tt>null</tt>, or if |
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* this map does not permit <tt>null</tt> keys or values, and the |
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* specified map contains <tt>null</tt> keys or values. |
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*/ |
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public void putAll(Map<? extends K, ? extends V> t) { |
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Iterator<? extends Entry<? extends K, ? extends V>> i = t.entrySet().iterator(); |
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while (i.hasNext()) { |
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Entry<? extends K, ? extends V> e = i.next(); |
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put(e.getKey(), e.getValue()); |
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} |
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} |
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/** |
322 |
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* Removes all mappings from this map (optional operation). <p> |
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* |
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* This implementation calls <tt>entrySet().clear()</tt>. |
325 |
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* |
326 |
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* Note that this implementation throws an |
327 |
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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 clear is not supported |
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* by this map. |
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*/ |
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public void clear() { |
334 |
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entrySet().clear(); |
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} |
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337 |
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// Views |
339 |
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/** |
341 |
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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. |
344 |
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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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348 |
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/** |
349 |
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* Returns a Set view of the keys contained in this map. The Set is |
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* backed by the map, so changes to the map are reflected in the Set, |
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* and vice-versa. (If the map is modified while an iteration over |
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* the Set is in progress, the results of the iteration are undefined.) |
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* The Set supports element removal, which removes the corresponding entry |
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* from the map, via the Iterator.remove, Set.remove, removeAll |
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* retainAll, and clear operations. It does not support the add or |
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* addAll operations.<p> |
357 |
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* |
358 |
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* This implementation returns a Set that subclasses |
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* AbstractSet. The subclass's iterator method returns a "wrapper |
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* object" over this map's entrySet() iterator. The size method delegates |
361 |
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* to this map's size method and the contains method delegates to this |
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* map's containsKey method.<p> |
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* |
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* 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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* @return a Set view of the keys contained in this map. |
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*/ |
371 |
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public Set<K> keySet() { |
372 |
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if (keySet == null) { |
373 |
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keySet = new AbstractSet<K>() { |
374 |
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public Iterator<K> iterator() { |
375 |
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return new Iterator<K>() { |
376 |
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private Iterator<Entry<K,V>> i = entrySet().iterator(); |
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378 |
|
|
public boolean hasNext() { |
379 |
|
|
return i.hasNext(); |
380 |
|
|
} |
381 |
|
|
|
382 |
|
|
public K next() { |
383 |
|
|
return i.next().getKey(); |
384 |
|
|
} |
385 |
|
|
|
386 |
|
|
public void remove() { |
387 |
|
|
i.remove(); |
388 |
|
|
} |
389 |
|
|
}; |
390 |
|
|
} |
391 |
|
|
|
392 |
|
|
public int size() { |
393 |
|
|
return AbstractMap.this.size(); |
394 |
|
|
} |
395 |
|
|
|
396 |
|
|
public boolean contains(Object k) { |
397 |
|
|
return AbstractMap.this.containsKey(k); |
398 |
|
|
} |
399 |
|
|
}; |
400 |
|
|
} |
401 |
|
|
return keySet; |
402 |
|
|
} |
403 |
|
|
|
404 |
|
|
/** |
405 |
|
|
* Returns a collection view of the values contained in this map. The |
406 |
|
|
* collection is backed by the map, so changes to the map are reflected in |
407 |
|
|
* the collection, and vice-versa. (If the map is modified while an |
408 |
|
|
* iteration over the collection is in progress, the results of the |
409 |
|
|
* iteration are undefined.) The collection supports element removal, |
410 |
|
|
* which removes the corresponding entry from the map, via the |
411 |
|
|
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>, |
412 |
|
|
* <tt>removeAll</tt>, <tt>retainAll</tt> and <tt>clear</tt> operations. |
413 |
|
|
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.<p> |
414 |
|
|
* |
415 |
|
|
* This implementation returns a collection that subclasses abstract |
416 |
|
|
* collection. The subclass's iterator method returns a "wrapper object" |
417 |
|
|
* over this map's <tt>entrySet()</tt> iterator. The size method |
418 |
|
|
* delegates to this map's size method and the contains method delegates |
419 |
|
|
* to this map's containsValue method.<p> |
420 |
|
|
* |
421 |
|
|
* The collection is created the first time this method is called, and |
422 |
|
|
* returned in response to all subsequent calls. No synchronization is |
423 |
|
|
* performed, so there is a slight chance that multiple calls to this |
424 |
|
|
* method will not all return the same Collection. |
425 |
|
|
* |
426 |
|
|
* @return a collection view of the values contained in this map. |
427 |
|
|
*/ |
428 |
|
|
public Collection<V> values() { |
429 |
|
|
if (values == null) { |
430 |
|
|
values = new AbstractCollection<V>() { |
431 |
|
|
public Iterator<V> iterator() { |
432 |
|
|
return new Iterator<V>() { |
433 |
|
|
private Iterator<Entry<K,V>> i = entrySet().iterator(); |
434 |
|
|
|
435 |
|
|
public boolean hasNext() { |
436 |
|
|
return i.hasNext(); |
437 |
|
|
} |
438 |
|
|
|
439 |
|
|
public V next() { |
440 |
|
|
return i.next().getValue(); |
441 |
|
|
} |
442 |
|
|
|
443 |
|
|
public void remove() { |
444 |
|
|
i.remove(); |
445 |
|
|
} |
446 |
|
|
}; |
447 |
|
|
} |
448 |
|
|
|
449 |
|
|
public int size() { |
450 |
|
|
return AbstractMap.this.size(); |
451 |
|
|
} |
452 |
|
|
|
453 |
|
|
public boolean contains(Object v) { |
454 |
|
|
return AbstractMap.this.containsValue(v); |
455 |
|
|
} |
456 |
|
|
}; |
457 |
|
|
} |
458 |
|
|
return values; |
459 |
|
|
} |
460 |
|
|
|
461 |
|
|
/** |
462 |
|
|
* Returns a set view of the mappings contained in this map. Each element |
463 |
|
|
* in this set is a Map.Entry. The set is backed by the map, so changes |
464 |
|
|
* to the map are reflected in the set, and vice-versa. (If the map is |
465 |
|
|
* modified while an iteration over the set is in progress, the results of |
466 |
|
|
* the iteration are undefined.) The set supports element removal, which |
467 |
|
|
* removes the corresponding entry from the map, via the |
468 |
|
|
* <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>, |
469 |
|
|
* <tt>retainAll</tt> and <tt>clear</tt> operations. It does not support |
470 |
|
|
* the <tt>add</tt> or <tt>addAll</tt> operations. |
471 |
|
|
* |
472 |
|
|
* @return a set view of the mappings contained in this map. |
473 |
|
|
*/ |
474 |
|
|
public abstract Set<Entry<K,V>> entrySet(); |
475 |
|
|
|
476 |
|
|
|
477 |
|
|
// Comparison and hashing |
478 |
|
|
|
479 |
|
|
/** |
480 |
|
|
* Compares the specified object with this map for equality. Returns |
481 |
|
|
* <tt>true</tt> if the given object is also a map and the two maps |
482 |
|
|
* represent the same mappings. More formally, two maps <tt>t1</tt> and |
483 |
|
|
* <tt>t2</tt> represent the same mappings if |
484 |
|
|
* <tt>t1.keySet().equals(t2.keySet())</tt> and for every key <tt>k</tt> |
485 |
|
|
* in <tt>t1.keySet()</tt>, <tt> (t1.get(k)==null ? t2.get(k)==null : |
486 |
|
|
* t1.get(k).equals(t2.get(k))) </tt>. This ensures that the |
487 |
|
|
* <tt>equals</tt> method works properly across different implementations |
488 |
|
|
* of the map interface.<p> |
489 |
|
|
* |
490 |
|
|
* This implementation first checks if the specified object is this map; |
491 |
|
|
* if so it returns <tt>true</tt>. Then, it checks if the specified |
492 |
|
|
* object is a map whose size is identical to the size of this set; if |
493 |
|
|
* not, it returns <tt>false</tt>. If so, it iterates over this map's |
494 |
|
|
* <tt>entrySet</tt> collection, and checks that the specified map |
495 |
|
|
* contains each mapping that this map contains. If the specified map |
496 |
|
|
* fails to contain such a mapping, <tt>false</tt> is returned. If the |
497 |
|
|
* iteration completes, <tt>true</tt> is returned. |
498 |
|
|
* |
499 |
|
|
* @param o object to be compared for equality with this map. |
500 |
|
|
* @return <tt>true</tt> if the specified object is equal to this map. |
501 |
|
|
*/ |
502 |
|
|
public boolean equals(Object o) { |
503 |
|
|
if (o == this) |
504 |
|
|
return true; |
505 |
|
|
|
506 |
|
|
if (!(o instanceof Map)) |
507 |
|
|
return false; |
508 |
|
|
Map<K,V> t = (Map<K,V>) o; |
509 |
|
|
if (t.size() != size()) |
510 |
|
|
return false; |
511 |
|
|
|
512 |
|
|
try { |
513 |
|
|
Iterator<Entry<K,V>> i = entrySet().iterator(); |
514 |
|
|
while (i.hasNext()) { |
515 |
|
|
Entry<K,V> e = i.next(); |
516 |
|
|
K key = e.getKey(); |
517 |
|
|
V value = e.getValue(); |
518 |
|
|
if (value == null) { |
519 |
|
|
if (!(t.get(key)==null && t.containsKey(key))) |
520 |
|
|
return false; |
521 |
|
|
} else { |
522 |
|
|
if (!value.equals(t.get(key))) |
523 |
|
|
return false; |
524 |
|
|
} |
525 |
|
|
} |
526 |
|
|
} catch(ClassCastException unused) { |
527 |
|
|
return false; |
528 |
|
|
} catch(NullPointerException unused) { |
529 |
|
|
return false; |
530 |
|
|
} |
531 |
|
|
|
532 |
|
|
return true; |
533 |
|
|
} |
534 |
|
|
|
535 |
|
|
/** |
536 |
|
|
* Returns the hash code value for this map. The hash code of a map is |
537 |
|
|
* defined to be the sum of the hash codes of each entry in the map's |
538 |
|
|
* <tt>entrySet()</tt> view. This ensures that <tt>t1.equals(t2)</tt> |
539 |
|
|
* implies that <tt>t1.hashCode()==t2.hashCode()</tt> for any two maps |
540 |
|
|
* <tt>t1</tt> and <tt>t2</tt>, as required by the general contract of |
541 |
|
|
* Object.hashCode.<p> |
542 |
|
|
* |
543 |
|
|
* This implementation iterates over <tt>entrySet()</tt>, calling |
544 |
|
|
* <tt>hashCode</tt> on each element (entry) in the Collection, and adding |
545 |
|
|
* up the results. |
546 |
|
|
* |
547 |
|
|
* @return the hash code value for this map. |
548 |
|
|
* @see Map.Entry#hashCode() |
549 |
|
|
* @see Object#hashCode() |
550 |
|
|
* @see Object#equals(Object) |
551 |
|
|
* @see Set#equals(Object) |
552 |
|
|
*/ |
553 |
|
|
public int hashCode() { |
554 |
|
|
int h = 0; |
555 |
|
|
Iterator<Entry<K,V>> i = entrySet().iterator(); |
556 |
|
|
while (i.hasNext()) |
557 |
|
|
h += i.next().hashCode(); |
558 |
|
|
return h; |
559 |
|
|
} |
560 |
|
|
|
561 |
|
|
/** |
562 |
|
|
* Returns a string representation of this map. The string representation |
563 |
|
|
* consists of a list of key-value mappings in the order returned by the |
564 |
|
|
* map's <tt>entrySet</tt> view's iterator, enclosed in braces |
565 |
|
|
* (<tt>"{}"</tt>). Adjacent mappings are separated by the characters |
566 |
|
|
* <tt>", "</tt> (comma and space). Each key-value mapping is rendered as |
567 |
|
|
* the key followed by an equals sign (<tt>"="</tt>) followed by the |
568 |
|
|
* associated value. Keys and values are converted to strings as by |
569 |
|
|
* <tt>String.valueOf(Object)</tt>.<p> |
570 |
|
|
* |
571 |
|
|
* This implementation creates an empty string buffer, appends a left |
572 |
|
|
* brace, and iterates over the map's <tt>entrySet</tt> view, appending |
573 |
|
|
* the string representation of each <tt>map.entry</tt> in turn. After |
574 |
|
|
* appending each entry except the last, the string <tt>", "</tt> is |
575 |
|
|
* appended. Finally a right brace is appended. A string is obtained |
576 |
|
|
* from the stringbuffer, and returned. |
577 |
|
|
* |
578 |
|
|
* @return a String representation of this map. |
579 |
|
|
*/ |
580 |
|
|
public String toString() { |
581 |
|
|
StringBuffer buf = new StringBuffer(); |
582 |
|
|
buf.append("{"); |
583 |
|
|
|
584 |
|
|
Iterator<Entry<K,V>> i = entrySet().iterator(); |
585 |
|
|
boolean hasNext = i.hasNext(); |
586 |
|
|
while (hasNext) { |
587 |
|
|
Entry<K,V> e = i.next(); |
588 |
|
|
K key = e.getKey(); |
589 |
|
|
V value = e.getValue(); |
590 |
|
|
if (key == this) |
591 |
|
|
buf.append("(this Map)"); |
592 |
|
|
else |
593 |
|
|
buf.append(key); |
594 |
|
|
buf.append("="); |
595 |
|
|
if (value == this) |
596 |
|
|
buf.append("(this Map)"); |
597 |
|
|
else |
598 |
|
|
buf.append(value); |
599 |
|
|
hasNext = i.hasNext(); |
600 |
|
|
if (hasNext) |
601 |
|
|
buf.append(", "); |
602 |
|
|
} |
603 |
|
|
|
604 |
|
|
buf.append("}"); |
605 |
|
|
return buf.toString(); |
606 |
|
|
} |
607 |
|
|
|
608 |
|
|
/** |
609 |
|
|
* Returns a shallow copy of this <tt>AbstractMap</tt> instance: the keys |
610 |
|
|
* and values themselves are not cloned. |
611 |
|
|
* |
612 |
|
|
* @return a shallow copy of this map. |
613 |
|
|
*/ |
614 |
|
|
protected Object clone() throws CloneNotSupportedException { |
615 |
|
|
AbstractMap<K,V> result = (AbstractMap<K,V>)super.clone(); |
616 |
|
|
result.keySet = null; |
617 |
|
|
result.values = null; |
618 |
|
|
return result; |
619 |
|
|
} |
620 |
|
|
|
621 |
|
|
/** |
622 |
|
|
* Utility method for SimpleEntry and SimpleImmutableEntry. |
623 |
|
|
* Test for equality, checking for nulls. |
624 |
|
|
*/ |
625 |
|
|
private static boolean eq(Object o1, Object o2) { |
626 |
|
|
return (o1 == null ? o2 == null : o1.equals(o2)); |
627 |
|
|
} |
628 |
|
|
|
629 |
|
|
// Implementation Note: SimpleEntry and SimpleImmutableEntry |
630 |
|
|
// are distinct unrelated classes, even though they share |
631 |
|
|
// some code. Since you can't add or subtract final-ness |
632 |
dl |
1.3 |
// of a field in a subclass, they can't share representations, |
633 |
dl |
1.1 |
// and the amount of duplicated code is too small to warrant |
634 |
|
|
// exposing a common abstract class. |
635 |
|
|
|
636 |
|
|
|
637 |
|
|
/** |
638 |
|
|
* An Entry maintaining a key and a value. The value may be |
639 |
|
|
* changed using the <tt>setValue</tt> method. This class |
640 |
|
|
* facilitates the process of building custom map |
641 |
|
|
* implementations. For example, it may be convenient to return |
642 |
|
|
* arrays of <tt>SimpleEntry</tt> instances in method |
643 |
|
|
* <tt>Map.entrySet().toArray</tt> |
644 |
|
|
*/ |
645 |
|
|
public static class SimpleEntry<K,V> implements Entry<K,V> { |
646 |
dl |
1.2 |
private final K key; |
647 |
dl |
1.1 |
private V value; |
648 |
|
|
|
649 |
|
|
/** |
650 |
|
|
* Creates an entry representing a mapping from the specified |
651 |
|
|
* key to the specified value. |
652 |
|
|
* |
653 |
|
|
* @param key the key represented by this entry |
654 |
|
|
* @param value the value represented by this entry |
655 |
|
|
*/ |
656 |
|
|
public SimpleEntry(K key, V value) { |
657 |
|
|
this.key = key; |
658 |
|
|
this.value = value; |
659 |
|
|
} |
660 |
|
|
|
661 |
|
|
/** |
662 |
|
|
* Creates an entry representing the same mapping as the |
663 |
|
|
* specified entry. |
664 |
|
|
* |
665 |
|
|
* @param entry the entry to copy. |
666 |
|
|
*/ |
667 |
dl |
1.4 |
public SimpleEntry(Entry<? extends K, ? extends V> entry) { |
668 |
dl |
1.1 |
this.key = entry.getKey(); |
669 |
|
|
this.value = entry.getValue(); |
670 |
|
|
} |
671 |
|
|
|
672 |
|
|
/** |
673 |
|
|
* Returns the key corresponding to this entry. |
674 |
|
|
* |
675 |
|
|
* @return the key corresponding to this entry. |
676 |
|
|
*/ |
677 |
|
|
public K getKey() { |
678 |
|
|
return key; |
679 |
|
|
} |
680 |
|
|
|
681 |
|
|
/** |
682 |
|
|
* Returns the value corresponding to this entry. |
683 |
|
|
* |
684 |
|
|
* @return the value corresponding to this entry. |
685 |
|
|
*/ |
686 |
|
|
public V getValue() { |
687 |
|
|
return value; |
688 |
|
|
} |
689 |
|
|
|
690 |
|
|
/** |
691 |
|
|
* Replaces the value corresponding to this entry with the specified |
692 |
|
|
* value. |
693 |
|
|
* |
694 |
|
|
* @param value new value to be stored in this entry. |
695 |
dl |
1.5 |
* @return the old value corresponding to the entry. |
696 |
dl |
1.1 |
*/ |
697 |
|
|
public V setValue(V value) { |
698 |
|
|
V oldValue = this.value; |
699 |
|
|
this.value = value; |
700 |
|
|
return oldValue; |
701 |
|
|
} |
702 |
|
|
|
703 |
|
|
public boolean equals(Object o) { |
704 |
|
|
if (!(o instanceof Map.Entry)) |
705 |
|
|
return false; |
706 |
|
|
Map.Entry e = (Map.Entry)o; |
707 |
|
|
return eq(key, e.getKey()) && eq(value, e.getValue()); |
708 |
|
|
} |
709 |
|
|
|
710 |
|
|
public int hashCode() { |
711 |
|
|
return ((key == null) ? 0 : key.hashCode()) ^ |
712 |
|
|
((value == null) ? 0 : value.hashCode()); |
713 |
|
|
} |
714 |
|
|
|
715 |
|
|
/** |
716 |
|
|
* Returns a String representation of this map entry. This |
717 |
|
|
* implementation returns the string representation of this |
718 |
|
|
* entry's key followed by the equals character ("<tt>=</tt>") |
719 |
|
|
* followed by the string representation of this entry's value. |
720 |
|
|
* |
721 |
|
|
* @return a String representation of this map entry. |
722 |
|
|
*/ |
723 |
|
|
public String toString() { |
724 |
|
|
return key + "=" + value; |
725 |
|
|
} |
726 |
|
|
|
727 |
|
|
} |
728 |
|
|
|
729 |
|
|
/** |
730 |
|
|
* An Entry maintaining an immutable key and value, This class |
731 |
|
|
* does not support method <tt>setValue</tt>. This class may be |
732 |
|
|
* convenient in methods that return thread-safe snapshots of |
733 |
|
|
* key-value mappings. |
734 |
|
|
*/ |
735 |
|
|
public static class SimpleImmutableEntry<K,V> implements Entry<K,V> { |
736 |
|
|
private final K key; |
737 |
|
|
private final V value; |
738 |
|
|
|
739 |
|
|
/** |
740 |
|
|
* Creates an entry representing a mapping from the specified |
741 |
|
|
* key to the specified value. |
742 |
|
|
* |
743 |
|
|
* @param key the key represented by this entry |
744 |
|
|
* @param value the value represented by this entry |
745 |
|
|
*/ |
746 |
|
|
public SimpleImmutableEntry(K key, V value) { |
747 |
|
|
this.key = key; |
748 |
|
|
this.value = value; |
749 |
|
|
} |
750 |
|
|
|
751 |
|
|
/** |
752 |
|
|
* Creates an entry representing the same mapping as the |
753 |
|
|
* specified entry. |
754 |
|
|
* |
755 |
|
|
* @param entry the entry to copy. |
756 |
|
|
*/ |
757 |
dl |
1.4 |
public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) { |
758 |
dl |
1.1 |
this.key = entry.getKey(); |
759 |
|
|
this.value = entry.getValue(); |
760 |
|
|
} |
761 |
|
|
|
762 |
|
|
/** |
763 |
|
|
* Returns the key corresponding to this entry. |
764 |
|
|
* |
765 |
|
|
* @return the key corresponding to this entry. |
766 |
|
|
*/ |
767 |
|
|
public K getKey() { |
768 |
|
|
return key; |
769 |
|
|
} |
770 |
|
|
|
771 |
|
|
/** |
772 |
|
|
* Returns the value corresponding to this entry. |
773 |
|
|
* |
774 |
|
|
* @return the value corresponding to this entry. |
775 |
|
|
*/ |
776 |
|
|
public V getValue() { |
777 |
|
|
return value; |
778 |
|
|
} |
779 |
|
|
|
780 |
|
|
/** |
781 |
|
|
* Replaces the value corresponding to this entry with the specified |
782 |
|
|
* value (optional operation). This implementation simply throws |
783 |
|
|
* <tt>UnsupportedOperationException</tt>, as this class implements |
784 |
|
|
* an <i>immutable</i> map entry. |
785 |
|
|
* |
786 |
|
|
* @param value new value to be stored in this entry. |
787 |
|
|
* @return (Does not return) |
788 |
|
|
* @throws UnsupportedOperationException always |
789 |
|
|
*/ |
790 |
|
|
public V setValue(V value) { |
791 |
|
|
throw new UnsupportedOperationException(); |
792 |
|
|
} |
793 |
|
|
|
794 |
|
|
public boolean equals(Object o) { |
795 |
|
|
if (!(o instanceof Map.Entry)) |
796 |
|
|
return false; |
797 |
|
|
Map.Entry e = (Map.Entry)o; |
798 |
|
|
return eq(key, e.getKey()) && eq(value, e.getValue()); |
799 |
|
|
} |
800 |
|
|
|
801 |
|
|
public int hashCode() { |
802 |
|
|
return ((key == null) ? 0 : key.hashCode()) ^ |
803 |
|
|
((value == null) ? 0 : value.hashCode()); |
804 |
|
|
} |
805 |
|
|
|
806 |
|
|
/** |
807 |
|
|
* Returns a String representation of this map entry. This |
808 |
|
|
* implementation returns the string representation of this |
809 |
|
|
* entry's key followed by the equals character ("<tt>=</tt>") |
810 |
|
|
* followed by the string representation of this entry's value. |
811 |
|
|
* |
812 |
|
|
* @return a String representation of this map entry. |
813 |
|
|
*/ |
814 |
|
|
public String toString() { |
815 |
|
|
return key + "=" + value; |
816 |
|
|
} |
817 |
|
|
|
818 |
|
|
} |
819 |
|
|
|
820 |
|
|
} |