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+/* Map.java: interface Map -- An object that maps keys to values
+             interface Map.Entry -- an Entry in a Map
+   Copyright (C) 1998, 2001, 2004, 2005  Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.util;
+
+/**
+ * An object that maps keys onto values. Keys cannot be duplicated. This
+ * interface replaces the obsolete {@link Dictionary} abstract class.
+ * <p>
+ *
+ * The map has three collection views, which are backed by the map
+ * (modifications on one show up on the other): a set of keys, a collection
+ * of values, and a set of key-value mappings. Some maps have a guaranteed
+ * order, but not all do.
+ * <p>
+ *
+ * Note: Be careful about using mutable keys.  Behavior is unspecified if
+ * a key's comparison behavior is changed after the fact.  As a corollary
+ * to this rule, don't use a Map as one of its own keys or values, as it makes
+ * hashCode and equals have undefined behavior.
+ * <p>
+ *
+ * All maps are recommended to provide a no argument constructor, which builds
+ * an empty map, and one that accepts a Map parameter and copies the mappings
+ * (usually by putAll), to create an equivalent map.  Unfortunately, Java
+ * cannot enforce these suggestions.
+ * <p>
+ *
+ * The map may be unmodifiable, in which case unsupported operations will
+ * throw an UnsupportedOperationException.  Note that some operations may be
+ * safe, such as putAll(m) where m is empty, even if the operation would
+ * normally fail with a non-empty argument.
+ *
+ * @author Original author unknown
+ * @author Eric Blake (ebb9@email.byu.edu)
+ * @see HashMap
+ * @see TreeMap
+ * @see Hashtable
+ * @see SortedMap
+ * @see Collection
+ * @see Set
+ * @since 1.2
+ * @status updated to 1.4
+ */
+public interface Map
+{
+  /**
+   * Remove all entries from this Map (optional operation).
+   *
+   * @throws UnsupportedOperationException if clear is not supported
+   */
+  void clear();
+
+  /**
+   * Returns true if this contains a mapping for the given key.
+   *
+   * @param key the key to search for
+   * @return true if the map contains the key
+   * @throws ClassCastException if the key is of an inappropriate type
+   * @throws NullPointerException if key is <code>null</code> but the map
+   *         does not permit null keys
+   */
+  boolean containsKey(Object key);
+
+  /**
+   * Returns true if this contains at least one mapping with the given value.
+   * In other words, returns true if a value v exists where
+   * <code>(value == null ? v == null : value.equals(v))</code>. This usually
+   * requires linear time.
+   *
+   * @param value the value to search for
+   * @return true if the map contains the value
+   * @throws ClassCastException if the type of the value is not a valid type
+   *         for this map.
+   * @throws NullPointerException if the value is null and the map doesn't
+   *         support null values.
+   */
+  boolean containsValue(Object value);
+
+  /**
+   * Returns a set view of the mappings in this Map.  Each element in the
+   * set is a Map.Entry.  The set is backed by the map, so that changes in
+   * one show up in the other.  Modifications made while an iterator is
+   * in progress cause undefined behavior.  If the set supports removal,
+   * these methods remove the underlying mapping from the map:
+   * <code>Iterator.remove</code>, <code>Set.remove</code>,
+   * <code>removeAll</code>, <code>retainAll</code>, and <code>clear</code>.
+   * Element addition, via <code>add</code> or <code>addAll</code>, is
+   * not supported via this set.
+   *
+   * @return the set view of all mapping entries
+   * @see Map.Entry
+   */
+  Set entrySet();
+
+  /**
+   * Compares the specified object with this map for equality. Returns
+   * <code>true</code> if the other object is a Map with the same mappings,
+   * that is,<br>
+   * <code>o instanceof Map && entrySet().equals(((Map) o).entrySet();</code>
+   * This allows comparison of maps, regardless of implementation.
+   *
+   * @param o the object to be compared
+   * @return true if the object equals this map
+   * @see Set#equals(Object)
+   */
+  boolean equals(Object o);
+
+  /**
+   * Returns the value mapped by the given key. Returns <code>null</code> if
+   * there is no mapping.  However, in Maps that accept null values, you
+   * must rely on <code>containsKey</code> to determine if a mapping exists.
+   *
+   * @param key the key to look up
+   * @return the value associated with the key, or null if key not in map
+   * @throws ClassCastException if the key is an inappropriate type
+   * @throws NullPointerException if this map does not accept null keys
+   * @see #containsKey(Object)
+   */
+  Object get(Object key);
+
+  /**
+   * Associates the given key to the given value (optional operation). If the
+   * map already contains the key, its value is replaced. Be aware that in
+   * a map that permits <code>null</code> values, a null return does not
+   * always imply that the mapping was created.
+   *
+   * @param key the key to map
+   * @param value the value to be mapped
+   * @return the previous value of the key, or null if there was no mapping
+   * @throws UnsupportedOperationException if the operation is not supported
+   * @throws ClassCastException if the key or value is of the wrong type
+   * @throws IllegalArgumentException if something about this key or value
+   *         prevents it from existing in this map
+   * @throws NullPointerException if either the key or the value is null,
+   *         and the map forbids null keys or values
+   * @see #containsKey(Object)
+   */
+  Object put(Object key, Object value);
+
+  /**
+   * Returns the hash code for this map. This is the sum of all hashcodes
+   * for each Map.Entry object in entrySet.  This allows comparison of maps,
+   * regardless of implementation, and satisfies the contract of
+   * Object.hashCode.
+   *
+   * @return the hash code
+   * @see Map.Entry#hashCode()
+   */
+  int hashCode();
+
+  /**
+   * Returns true if the map contains no mappings.
+   *
+   * @return true if the map is empty
+   */
+  boolean isEmpty();
+
+  /**
+   * Returns a set view of the keys in this Map.  The set is backed by the
+   * map, so that changes in one show up in the other.  Modifications made
+   * while an iterator is in progress cause undefined behavior.  If the set
+   * supports removal, these methods remove the underlying mapping from
+   * the map: <code>Iterator.remove</code>, <code>Set.remove</code>,
+   * <code>removeAll</code>, <code>retainAll</code>, and <code>clear</code>.
+   * Element addition, via <code>add</code> or <code>addAll</code>, is
+   * not supported via this set.
+   *
+   * @return the set view of all keys
+   */
+  Set keySet();
+
+  /**
+   * Copies all entries of the given map to this one (optional operation). If
+   * the map already contains a key, its value is replaced.
+   *
+   * @param m the mapping to load into this map
+   * @throws UnsupportedOperationException if the operation is not supported
+   * @throws ClassCastException if a key or value is of the wrong type
+   * @throws IllegalArgumentException if something about a key or value
+   *         prevents it from existing in this map
+   * @throws NullPointerException if the map forbids null keys or values, or
+   *         if <code>m</code> is null.
+   * @see #put(Object, Object)
+   */
+  void putAll(Map m);
+
+  /**
+   * Removes the mapping for this key if present (optional operation). If
+   * the key is not present, this returns null. Note that maps which permit
+   * null values may also return null if the key was removed.
+   *
+   * @param key the key to remove
+   * @return the value the key mapped to, or null if not present.
+   * @throws UnsupportedOperationException if deletion is unsupported
+   * @throws NullPointerException if the key is null and this map doesn't
+   *         support null keys.
+   * @throws ClassCastException if the type of the key is not a valid type
+   *         for this map.
+   */
+  Object remove(Object key);
+
+  /**
+   * Returns the number of key-value mappings in the map. If there are more
+   * than Integer.MAX_VALUE mappings, return Integer.MAX_VALUE.
+   *
+   * @return the number of mappings
+   */
+  int size();
+
+  /**
+   * Returns a collection (or bag) view of the values in this Map.  The
+   * collection is backed by the map, so that changes in one show up in
+   * the other.  Modifications made while an iterator is in progress cause
+   * undefined behavior.  If the collection supports removal, these methods
+   * remove the underlying mapping from the map: <code>Iterator.remove</code>,
+   * <code>Collection.remove</code>, <code>removeAll</code>,
+   * <code>retainAll</code>, and <code>clear</code>. Element addition, via
+   * <code>add</code> or <code>addAll</code>, is not supported via this
+   * collection.
+   *
+   * @return the collection view of all values
+   */
+  Collection values();
+
+  /**
+   * A map entry (key-value pair). The Map.entrySet() method returns a set
+   * view of these objects; there is no other valid way to come across them.
+   * These objects are only valid for the duration of an iteration; in other
+   * words, if you mess with one after modifying the map, you are asking
+   * for undefined behavior.
+   *
+   * @author Original author unknown
+   * @author Eric Blake (ebb9@email.byu.edu)
+   * @see Map
+   * @see Map#entrySet()
+   * @since 1.2
+   * @status updated to 1.4
+   */
+  interface Entry
+  {
+    /**
+     * Get the key corresponding to this entry.
+     *
+     * @return the key
+     */
+    Object getKey();
+
+    /**
+     * Get the value corresponding to this entry. If you already called
+     * Iterator.remove(), this is undefined.
+     *
+     * @return the value
+     */
+    Object getValue();
+
+    /**
+     * Replaces the value with the specified object (optional operation).
+     * This writes through to the map, and is undefined if you already
+     * called Iterator.remove().
+     *
+     * @param value the new value to store
+     * @return the old value
+     * @throws UnsupportedOperationException if the operation is not supported
+     * @throws ClassCastException if the value is of the wrong type
+     * @throws IllegalArgumentException if something about the value
+     *         prevents it from existing in this map
+     * @throws NullPointerException if the map forbids null values
+     */
+    Object setValue(Object value);
+
+
+    /**
+     * Returns the hash code of the entry.  This is defined as the
+     * exclusive-or of the hashcodes of the key and value (using 0 for
+     * <code>null</code>). In other words, this must be:
+     * 
+<p><pre>(getKey() == null ? 0 : getKey().hashCode())
+^ (getValue() == null ? 0 : getValue().hashCode())</pre>
+     *
+     * @return the hash code
+     */
+    int hashCode();
+
+    /**
+     * Compares the specified object with this entry. Returns true only if
+     * the object is a mapping of identical key and value. In other words,
+     * this must be:
+     * 
+<p><pre>(o instanceof Map.Entry)
+&& (getKey() == null ? ((HashMap) o).getKey() == null
+                     : getKey().equals(((HashMap) o).getKey()))
+&& (getValue() == null ? ((HashMap) o).getValue() == null
+                       : getValue().equals(((HashMap) o).getValue()))</pre>
+     *
+     * @param o the object to compare
+     *
+     * @return <code>true</code> if it is equal
+     */
+    boolean equals(Object o);
+  }
+}