--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/Map.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,469 @@
+/*
+ * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package java.util;
+
+/**
+ * An object that maps keys to values. A map cannot contain duplicate keys;
+ * each key can map to at most one value.
+ *
+ * <p>This interface takes the place of the <tt>Dictionary</tt> class, which
+ * was a totally abstract class rather than an interface.
+ *
+ * <p>The <tt>Map</tt> interface provides three <i>collection views</i>, which
+ * allow a map's contents to be viewed as a set of keys, collection of values,
+ * or set of key-value mappings. The <i>order</i> of a map is defined as
+ * the order in which the iterators on the map's collection views return their
+ * elements. Some map implementations, like the <tt>TreeMap</tt> class, make
+ * specific guarantees as to their order; others, like the <tt>HashMap</tt>
+ * class, do not.
+ *
+ * <p>Note: great care must be exercised if mutable objects are used as map
+ * keys. The behavior of a map is not specified if the value of an object is
+ * changed in a manner that affects <tt>equals</tt> comparisons while the
+ * object is a key in the map. A special case of this prohibition is that it
+ * is not permissible for a map to contain itself as a key. While it is
+ * permissible for a map to contain itself as a value, extreme caution is
+ * advised: the <tt>equals</tt> and <tt>hashCode</tt> methods are no longer
+ * well defined on such a map.
+ *
+ * <p>All general-purpose map implementation classes should provide two
+ * "standard" constructors: a void (no arguments) constructor which creates an
+ * empty map, and a constructor with a single argument of type <tt>Map</tt>,
+ * which creates a new map with the same key-value mappings as its argument.
+ * In effect, the latter constructor allows the user to copy any map,
+ * producing an equivalent map of the desired class. There is no way to
+ * enforce this recommendation (as interfaces cannot contain constructors) but
+ * all of the general-purpose map implementations in the JDK comply.
+ *
+ * <p>The "destructive" methods contained in this interface, that is, the
+ * methods that modify the map on which they operate, are specified to throw
+ * <tt>UnsupportedOperationException</tt> if this map does not support the
+ * operation. If this is the case, these methods may, but are not required
+ * to, throw an <tt>UnsupportedOperationException</tt> if the invocation would
+ * have no effect on the map. For example, invoking the {@link #putAll(Map)}
+ * method on an unmodifiable map may, but is not required to, throw the
+ * exception if the map whose mappings are to be "superimposed" is empty.
+ *
+ * <p>Some map implementations have restrictions on the keys and values they
+ * may contain. For example, some implementations prohibit null keys and
+ * values, and some have restrictions on the types of their keys. Attempting
+ * to insert an ineligible key or value throws an unchecked exception,
+ * typically <tt>NullPointerException</tt> or <tt>ClassCastException</tt>.
+ * Attempting to query the presence of an ineligible key or value may throw an
+ * exception, or it may simply return false; some implementations will exhibit
+ * the former behavior and some will exhibit the latter. More generally,
+ * attempting an operation on an ineligible key or value whose completion
+ * would not result in the insertion of an ineligible element into the map may
+ * throw an exception or it may succeed, at the option of the implementation.
+ * Such exceptions are marked as "optional" in the specification for this
+ * interface.
+ *
+ * <p>This interface is a member of the
+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * <p>Many methods in Collections Framework interfaces are defined
+ * in terms of the {@link Object#equals(Object) equals} method. For
+ * example, the specification for the {@link #containsKey(Object)
+ * containsKey(Object key)} method says: "returns <tt>true</tt> if and
+ * only if this map contains a mapping for a key <tt>k</tt> such that
+ * <tt>(key==null ? k==null : key.equals(k))</tt>." This specification should
+ * <i>not</i> be construed to imply that invoking <tt>Map.containsKey</tt>
+ * with a non-null argument <tt>key</tt> will cause <tt>key.equals(k)</tt> to
+ * be invoked for any key <tt>k</tt>. Implementations are free to
+ * implement optimizations whereby the <tt>equals</tt> invocation is avoided,
+ * for example, by first comparing the hash codes of the two keys. (The
+ * {@link Object#hashCode()} specification guarantees that two objects with
+ * unequal hash codes cannot be equal.) More generally, implementations of
+ * the various Collections Framework interfaces are free to take advantage of
+ * the specified behavior of underlying {@link Object} methods wherever the
+ * implementor deems it appropriate.
+ *
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ *
+ * @author Josh Bloch
+ * @see HashMap
+ * @see TreeMap
+ * @see Hashtable
+ * @see SortedMap
+ * @see Collection
+ * @see Set
+ * @since 1.2
+ */
+public interface Map<K,V> {
+ // Query Operations
+
+ /**
+ * Returns the number of key-value mappings in this map. If the
+ * map contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
+ * <tt>Integer.MAX_VALUE</tt>.
+ *
+ * @return the number of key-value mappings in this map
+ */
+ int size();
+
+ /**
+ * Returns <tt>true</tt> if this map contains no key-value mappings.
+ *
+ * @return <tt>true</tt> if this map contains no key-value mappings
+ */
+ boolean isEmpty();
+
+ /**
+ * Returns <tt>true</tt> if this map contains a mapping for the specified
+ * key. More formally, returns <tt>true</tt> if and only if
+ * this map contains a mapping for a key <tt>k</tt> such that
+ * <tt>(key==null ? k==null : key.equals(k))</tt>. (There can be
+ * at most one such mapping.)
+ *
+ * @param key key whose presence in this map is to be tested
+ * @return <tt>true</tt> if this map contains a mapping for the specified
+ * key
+ * @throws ClassCastException if the key is of an inappropriate type for
+ * this map (optional)
+ * @throws NullPointerException if the specified key is null and this map
+ * does not permit null keys (optional)
+ */
+ boolean containsKey(Object key);
+
+ /**
+ * Returns <tt>true</tt> if this map maps one or more keys to the
+ * specified value. More formally, returns <tt>true</tt> if and only if
+ * this map contains at least one mapping to a value <tt>v</tt> such that
+ * <tt>(value==null ? v==null : value.equals(v))</tt>. This operation
+ * will probably require time linear in the map size for most
+ * implementations of the <tt>Map</tt> interface.
+ *
+ * @param value value whose presence in this map is to be tested
+ * @return <tt>true</tt> if this map maps one or more keys to the
+ * specified value
+ * @throws ClassCastException if the value is of an inappropriate type for
+ * this map (optional)
+ * @throws NullPointerException if the specified value is null and this
+ * map does not permit null values (optional)
+ */
+ boolean containsValue(Object value);
+
+ /**
+ * Returns the value to which the specified key is mapped,
+ * or {@code null} if this map contains no mapping for the key.
+ *
+ * <p>More formally, if this map contains a mapping from a key
+ * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
+ * key.equals(k))}, then this method returns {@code v}; otherwise
+ * it returns {@code null}. (There can be at most one such mapping.)
+ *
+ * <p>If this map permits null values, then a return value of
+ * {@code null} does not <i>necessarily</i> indicate that the map
+ * contains no mapping for the key; it's also possible that the map
+ * explicitly maps the key to {@code null}. The {@link #containsKey
+ * containsKey} operation may be used to distinguish these two cases.
+ *
+ * @param key the key whose associated value is to be returned
+ * @return the value to which the specified key is mapped, or
+ * {@code null} if this map contains no mapping for the key
+ * @throws ClassCastException if the key is of an inappropriate type for
+ * this map (optional)
+ * @throws NullPointerException if the specified key is null and this map
+ * does not permit null keys (optional)
+ */
+ V get(Object key);
+
+ // Modification Operations
+
+ /**
+ * Associates the specified value with the specified key in this map
+ * (optional operation). If the map previously contained a mapping for
+ * the key, the old value is replaced by the specified value. (A map
+ * <tt>m</tt> is said to contain a mapping for a key <tt>k</tt> if and only
+ * if {@link #containsKey(Object) m.containsKey(k)} would return
+ * <tt>true</tt>.)
+ *
+ * @param key key with which the specified value is to be associated
+ * @param value value to be associated with the specified key
+ * @return the previous value associated with <tt>key</tt>, or
+ * <tt>null</tt> if there was no mapping for <tt>key</tt>.
+ * (A <tt>null</tt> return can also indicate that the map
+ * previously associated <tt>null</tt> with <tt>key</tt>,
+ * if the implementation supports <tt>null</tt> values.)
+ * @throws UnsupportedOperationException if the <tt>put</tt> operation
+ * is not supported by this map
+ * @throws ClassCastException if the class of the specified key or value
+ * prevents it from being stored in this map
+ * @throws NullPointerException if the specified key or value is null
+ * and this map does not permit null keys or values
+ * @throws IllegalArgumentException if some property of the specified key
+ * or value prevents it from being stored in this map
+ */
+ V put(K key, V value);
+
+ /**
+ * Removes the mapping for a key from this map if it is present
+ * (optional operation). More formally, if this map contains a mapping
+ * from key <tt>k</tt> to value <tt>v</tt> such that
+ * <code>(key==null ? k==null : key.equals(k))</code>, that mapping
+ * is removed. (The map can contain at most one such mapping.)
+ *
+ * <p>Returns the value to which this map previously associated the key,
+ * or <tt>null</tt> if the map contained no mapping for the key.
+ *
+ * <p>If this map permits null values, then a return value of
+ * <tt>null</tt> does not <i>necessarily</i> indicate that the map
+ * contained no mapping for the key; it's also possible that the map
+ * explicitly mapped the key to <tt>null</tt>.
+ *
+ * <p>The map will not contain a mapping for the specified key once the
+ * call returns.
+ *
+ * @param key key whose mapping is to be removed from the map
+ * @return the previous value associated with <tt>key</tt>, or
+ * <tt>null</tt> if there was no mapping for <tt>key</tt>.
+ * @throws UnsupportedOperationException if the <tt>remove</tt> operation
+ * is not supported by this map
+ * @throws ClassCastException if the key is of an inappropriate type for
+ * this map (optional)
+ * @throws NullPointerException if the specified key is null and this
+ * map does not permit null keys (optional)
+ */
+ V remove(Object key);
+
+
+ // Bulk Operations
+
+ /**
+ * Copies all of the mappings from the specified map to this map
+ * (optional operation). The effect of this call is equivalent to that
+ * of calling {@link #put(Object,Object) put(k, v)} on this map once
+ * for each mapping from key <tt>k</tt> to value <tt>v</tt> in the
+ * specified map. The behavior of this operation is undefined if the
+ * specified map is modified while the operation is in progress.
+ *
+ * @param m mappings to be stored in this map
+ * @throws UnsupportedOperationException if the <tt>putAll</tt> operation
+ * is not supported by this map
+ * @throws ClassCastException if the class of a key or value in the
+ * specified map prevents it from being stored in this map
+ * @throws NullPointerException if the specified map is null, or if
+ * this map does not permit null keys or values, and the
+ * specified map contains null keys or values
+ * @throws IllegalArgumentException if some property of a key or value in
+ * the specified map prevents it from being stored in this map
+ */
+ void putAll(Map<? extends K, ? extends V> m);
+
+ /**
+ * Removes all of the mappings from this map (optional operation).
+ * The map will be empty after this call returns.
+ *
+ * @throws UnsupportedOperationException if the <tt>clear</tt> operation
+ * is not supported by this map
+ */
+ void clear();
+
+
+ // Views
+
+ /**
+ * Returns a {@link Set} view of the keys contained in this map.
+ * The set is backed by the map, so changes to the map are
+ * reflected in the set, and vice-versa. If the map is modified
+ * while an iteration over the set is in progress (except through
+ * the iterator's own <tt>remove</tt> operation), the results of
+ * the iteration are undefined. The set supports element removal,
+ * which removes the corresponding mapping from the map, via the
+ * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
+ * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
+ * operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
+ * operations.
+ *
+ * @return a set view of the keys contained in this map
+ */
+ Set<K> keySet();
+
+ /**
+ * Returns a {@link Collection} view of the values contained in this map.
+ * The collection is backed by the map, so changes to the map are
+ * reflected in the collection, and vice-versa. If the map is
+ * modified while an iteration over the collection is in progress
+ * (except through the iterator's own <tt>remove</tt> operation),
+ * the results of the iteration are undefined. The collection
+ * supports element removal, which removes the corresponding
+ * mapping from the map, via the <tt>Iterator.remove</tt>,
+ * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
+ * <tt>retainAll</tt> and <tt>clear</tt> operations. It does not
+ * support the <tt>add</tt> or <tt>addAll</tt> operations.
+ *
+ * @return a collection view of the values contained in this map
+ */
+ Collection<V> values();
+
+ /**
+ * Returns a {@link Set} view of the mappings contained in this map.
+ * The set is backed by the map, so changes to the map are
+ * reflected in the set, and vice-versa. If the map is modified
+ * while an iteration over the set is in progress (except through
+ * the iterator's own <tt>remove</tt> operation, or through the
+ * <tt>setValue</tt> operation on a map entry returned by the
+ * iterator) the results of the iteration are undefined. The set
+ * supports element removal, which removes the corresponding
+ * mapping from the map, via the <tt>Iterator.remove</tt>,
+ * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
+ * <tt>clear</tt> operations. It does not support the
+ * <tt>add</tt> or <tt>addAll</tt> operations.
+ *
+ * @return a set view of the mappings contained in this map
+ */
+ Set<Map.Entry<K, V>> entrySet();
+
+ /**
+ * A map entry (key-value pair). The <tt>Map.entrySet</tt> method returns
+ * a collection-view of the map, whose elements are of this class. The
+ * <i>only</i> way to obtain a reference to a map entry is from the
+ * iterator of this collection-view. These <tt>Map.Entry</tt> objects are
+ * valid <i>only</i> for the duration of the iteration; more formally,
+ * the behavior of a map entry is undefined if the backing map has been
+ * modified after the entry was returned by the iterator, except through
+ * the <tt>setValue</tt> operation on the map entry.
+ *
+ * @see Map#entrySet()
+ * @since 1.2
+ */
+ interface Entry<K,V> {
+ /**
+ * Returns the key corresponding to this entry.
+ *
+ * @return the key corresponding to this entry
+ * @throws IllegalStateException implementations may, but are not
+ * required to, throw this exception if the entry has been
+ * removed from the backing map.
+ */
+ K getKey();
+
+ /**
+ * Returns the value corresponding to this entry. If the mapping
+ * has been removed from the backing map (by the iterator's
+ * <tt>remove</tt> operation), the results of this call are undefined.
+ *
+ * @return the value corresponding to this entry
+ * @throws IllegalStateException implementations may, but are not
+ * required to, throw this exception if the entry has been
+ * removed from the backing map.
+ */
+ V getValue();
+
+ /**
+ * Replaces the value corresponding to this entry with the specified
+ * value (optional operation). (Writes through to the map.) The
+ * behavior of this call is undefined if the mapping has already been
+ * removed from the map (by the iterator's <tt>remove</tt> operation).
+ *
+ * @param value new value to be stored in this entry
+ * @return old value corresponding to the entry
+ * @throws UnsupportedOperationException if the <tt>put</tt> operation
+ * is not supported by the backing map
+ * @throws ClassCastException if the class of the specified value
+ * prevents it from being stored in the backing map
+ * @throws NullPointerException if the backing map does not permit
+ * null values, and the specified value is null
+ * @throws IllegalArgumentException if some property of this value
+ * prevents it from being stored in the backing map
+ * @throws IllegalStateException implementations may, but are not
+ * required to, throw this exception if the entry has been
+ * removed from the backing map.
+ */
+ V setValue(V value);
+
+ /**
+ * Compares the specified object with this entry for equality.
+ * Returns <tt>true</tt> if the given object is also a map entry and
+ * the two entries represent the same mapping. More formally, two
+ * entries <tt>e1</tt> and <tt>e2</tt> represent the same mapping
+ * if<pre>
+ * (e1.getKey()==null ?
+ * e2.getKey()==null : e1.getKey().equals(e2.getKey())) &&
+ * (e1.getValue()==null ?
+ * e2.getValue()==null : e1.getValue().equals(e2.getValue()))
+ * </pre>
+ * This ensures that the <tt>equals</tt> method works properly across
+ * different implementations of the <tt>Map.Entry</tt> interface.
+ *
+ * @param o object to be compared for equality with this map entry
+ * @return <tt>true</tt> if the specified object is equal to this map
+ * entry
+ */
+ boolean equals(Object o);
+
+ /**
+ * Returns the hash code value for this map entry. The hash code
+ * of a map entry <tt>e</tt> is defined to be: <pre>
+ * (e.getKey()==null ? 0 : e.getKey().hashCode()) ^
+ * (e.getValue()==null ? 0 : e.getValue().hashCode())
+ * </pre>
+ * This ensures that <tt>e1.equals(e2)</tt> implies that
+ * <tt>e1.hashCode()==e2.hashCode()</tt> for any two Entries
+ * <tt>e1</tt> and <tt>e2</tt>, as required by the general
+ * contract of <tt>Object.hashCode</tt>.
+ *
+ * @return the hash code value for this map entry
+ * @see Object#hashCode()
+ * @see Object#equals(Object)
+ * @see #equals(Object)
+ */
+ int hashCode();
+ }
+
+ // Comparison and hashing
+
+ /**
+ * Compares the specified object with this map for equality. Returns
+ * <tt>true</tt> if the given object is also a map and the two maps
+ * represent the same mappings. More formally, two maps <tt>m1</tt> and
+ * <tt>m2</tt> represent the same mappings if
+ * <tt>m1.entrySet().equals(m2.entrySet())</tt>. This ensures that the
+ * <tt>equals</tt> method works properly across different implementations
+ * of the <tt>Map</tt> interface.
+ *
+ * @param o object to be compared for equality with this map
+ * @return <tt>true</tt> if the specified object is equal to this map
+ */
+ boolean equals(Object o);
+
+ /**
+ * Returns the hash code value for this map. The hash code of a map is
+ * defined to be the sum of the hash codes of each entry in the map's
+ * <tt>entrySet()</tt> view. This ensures that <tt>m1.equals(m2)</tt>
+ * implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two maps
+ * <tt>m1</tt> and <tt>m2</tt>, as required by the general contract of
+ * {@link Object#hashCode}.
+ *
+ * @return the hash code value for this map
+ * @see Map.Entry#hashCode()
+ * @see Object#equals(Object)
+ * @see #equals(Object)
+ */
+ int hashCode();
+}