| /* 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. |
| |
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| 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 |
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| 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 |
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| 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 ? ((Map.Entry) o).getKey() == null |
| : getKey().equals(((Map.Entry) o).getKey())) |
| && (getValue() == null ? ((Map.Entry) o).getValue() == null |
| : getValue().equals(((Map.Entry) o).getValue()))</pre> |
| * |
| * @param o the object to compare |
| * |
| * @return <code>true</code> if it is equal |
| */ |
| boolean equals(Object o); |
| } |
| } |