mirror of git://gcc.gnu.org/git/gcc.git
648 lines
20 KiB
Java
648 lines
20 KiB
Java
/* AbstractMap.java -- Abstract implementation of most of Map
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Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.util;
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/**
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* An abstract implementation of Map to make it easier to create your own
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* implementations. In order to create an unmodifiable Map, subclass
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* AbstractMap and implement the <code>entrySet</code> (usually via an
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* AbstractSet). To make it modifiable, also implement <code>put</code>,
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* and have <code>entrySet().iterator()</code> support <code>remove</code>.
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* <p>
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*
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* It is recommended that classes which extend this support at least the
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* no-argument constructor, and a constructor which accepts another Map.
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* Further methods in this class may be overridden if you have a more
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* efficient implementation.
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*
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* @author Original author unknown
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* @author Bryce McKinlay
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* @author Eric Blake <ebb9@email.byu.edu>
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* @see Map
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* @see Collection
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* @see HashMap
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* @see LinkedHashMap
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* @see TreeMap
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* @see WeakHashMap
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* @see IdentityHashMap
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* @since 1.2
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* @status updated to 1.4
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*/
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public abstract class AbstractMap implements Map
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{
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/** An "enum" of iterator types. */
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// Package visible for use by subclasses.
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static final int KEYS = 0,
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VALUES = 1,
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ENTRIES = 2;
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/**
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* The cache for {@link #keySet()}.
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*/
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// Package visible for use by subclasses.
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Set keys;
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/**
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* The cache for {@link #values()}.
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*/
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// Package visible for use by subclasses.
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Collection values;
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/**
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* The main constructor, for use by subclasses.
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*/
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protected AbstractMap()
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{
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}
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/**
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* Remove all entries from this Map (optional operation). This default
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* implementation calls entrySet().clear(). NOTE: If the entry set does
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* not permit clearing, then this will fail, too. Subclasses often
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* override this for efficiency. Your implementation of entrySet() should
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* not call <code>AbstractMap.clear</code> unless you want an infinite loop.
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*
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* @throws UnsupportedOperationException if <code>entrySet().clear()</code>
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* does not support clearing.
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* @see Set#clear()
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*/
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public void clear()
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{
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entrySet().clear();
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}
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/**
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* Create a shallow copy of this Map, no keys or values are copied. The
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* default implementation simply calls <code>super.clone()</code>.
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*
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* @return the shallow clone
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* @throws CloneNotSupportedException if a subclass is not Cloneable
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* @see Cloneable
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* @see Object#clone()
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*/
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protected Object clone() throws CloneNotSupportedException
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{
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AbstractMap copy = (AbstractMap) super.clone();
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// Clear out the caches; they are stale.
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copy.keys = null;
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copy.values = null;
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return copy;
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}
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/**
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* Returns true if this contains a mapping for the given key. This
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* implementation does a linear search, O(n), over the
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* <code>entrySet()</code>, returning <code>true</code> if a match
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* is found, <code>false</code> if the iteration ends. Many subclasses
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* can implement this more efficiently.
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*
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* @param key the key to search for
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* @return true if the map contains the key
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* @throws NullPointerException if key is <code>null</code> but the map
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* does not permit null keys
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* @see #containsValue(Object)
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*/
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public boolean containsKey(Object key)
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{
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Iterator entries = entrySet().iterator();
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int pos = size();
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while (--pos >= 0)
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if (equals(key, ((Map.Entry) entries.next()).getKey()))
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return true;
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return false;
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}
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/**
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* Returns true if this contains at least one mapping with the given value.
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* This implementation does a linear search, O(n), over the
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* <code>entrySet()</code>, returning <code>true</code> if a match
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* is found, <code>false</code> if the iteration ends. A match is
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* defined as <code>(value == null ? v == null : value.equals(v))</code>
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* Subclasses are unlikely to implement this more efficiently.
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*
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* @param value the value to search for
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* @return true if the map contains the value
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* @see #containsKey(Object)
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*/
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public boolean containsValue(Object value)
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{
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Iterator entries = entrySet().iterator();
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int pos = size();
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while (--pos >= 0)
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if (equals(value, ((Map.Entry) entries.next()).getValue()))
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return true;
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return false;
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}
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/**
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* Returns a set view of the mappings in this Map. Each element in the
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* set must be an implementation of Map.Entry. The set is backed by
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* the map, so that changes in one show up in the other. Modifications
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* made while an iterator is in progress cause undefined behavior. If
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* the set supports removal, these methods must be valid:
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* <code>Iterator.remove</code>, <code>Set.remove</code>,
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* <code>removeAll</code>, <code>retainAll</code>, and <code>clear</code>.
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* Element addition is not supported via this set.
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*
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* @return the entry set
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* @see Map.Entry
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*/
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public abstract Set entrySet();
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/**
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* Compares the specified object with this map for equality. Returns
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* <code>true</code> if the other object is a Map with the same mappings,
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* that is,<br>
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* <code>o instanceof Map && entrySet().equals(((Map) o).entrySet();</code>
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*
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* @param o the object to be compared
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* @return true if the object equals this map
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* @see Set#equals(Object)
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*/
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public boolean equals(Object o)
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{
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return (o == this ||
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(o instanceof Map &&
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entrySet().equals(((Map) o).entrySet())));
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}
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/**
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* Returns the value mapped by the given key. Returns <code>null</code> if
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* there is no mapping. However, in Maps that accept null values, you
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* must rely on <code>containsKey</code> to determine if a mapping exists.
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* This iteration takes linear time, searching entrySet().iterator() of
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* the key. Many implementations override this method.
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*
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* @param key the key to look up
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* @return the value associated with the key, or null if key not in map
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* @throws NullPointerException if this map does not accept null keys
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* @see #containsKey(Object)
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*/
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public Object get(Object key)
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{
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Iterator entries = entrySet().iterator();
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int pos = size();
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while (--pos >= 0)
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{
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Map.Entry entry = (Map.Entry) entries.next();
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if (equals(key, entry.getKey()))
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return entry.getValue();
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}
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return null;
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}
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/**
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* Returns the hash code for this map. As defined in Map, this is the sum
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* of all hashcodes for each Map.Entry object in entrySet, or basically
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* entrySet().hashCode().
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*
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* @return the hash code
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* @see Map.Entry#hashCode()
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* @see Set#hashCode()
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*/
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public int hashCode()
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{
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return entrySet().hashCode();
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}
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/**
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* Returns true if the map contains no mappings. This is implemented by
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* <code>size() == 0</code>.
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*
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* @return true if the map is empty
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* @see #size()
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*/
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public boolean isEmpty()
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{
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return size() == 0;
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}
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/**
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* Returns a set view of this map's keys. The set is backed by the map,
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* so changes in one show up in the other. Modifications while an iteration
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* is in progress produce undefined behavior. The set supports removal
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* if entrySet() does, but does not support element addition.
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* <p>
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*
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* This implementation creates an AbstractSet, where the iterator wraps
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* the entrySet iterator, size defers to the Map's size, and contains
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* defers to the Map's containsKey. The set is created on first use, and
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* returned on subsequent uses, although since no synchronization occurs,
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* there is a slight possibility of creating two sets.
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*
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* @return a Set view of the keys
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* @see Set#iterator()
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* @see #size()
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* @see #containsKey(Object)
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* @see #values()
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*/
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public Set keySet()
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{
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if (keys == null)
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keys = new AbstractSet()
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{
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public int size()
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{
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return AbstractMap.this.size();
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}
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public boolean contains(Object key)
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{
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return containsKey(key);
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}
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public Iterator iterator()
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{
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return new Iterator()
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{
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private final Iterator map_iterator = entrySet().iterator();
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public boolean hasNext()
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{
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return map_iterator.hasNext();
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}
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public Object next()
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{
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return ((Map.Entry) map_iterator.next()).getKey();
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}
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public void remove()
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{
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map_iterator.remove();
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}
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};
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}
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};
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return keys;
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}
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/**
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* Associates the given key to the given value (optional operation). If the
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* map already contains the key, its value is replaced. This implementation
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* simply throws an UnsupportedOperationException. Be aware that in a map
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* that permits <code>null</code> values, a null return does not always
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* imply that the mapping was created.
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*
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* @param key the key to map
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* @param value the value to be mapped
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* @return the previous value of the key, or null if there was no mapping
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* @throws UnsupportedOperationException if the operation is not supported
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* @throws ClassCastException if the key or value is of the wrong type
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* @throws IllegalArgumentException if something about this key or value
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* prevents it from existing in this map
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* @throws NullPointerException if the map forbids null keys or values
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* @see #containsKey(Object)
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*/
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public Object put(Object key, Object value)
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{
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throw new UnsupportedOperationException();
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}
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/**
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* Copies all entries of the given map to this one (optional operation). If
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* the map already contains a key, its value is replaced. This implementation
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* simply iterates over the map's entrySet(), calling <code>put</code>,
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* so it is not supported if puts are not.
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*
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* @param m the mapping to load into this map
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* @throws UnsupportedOperationException if the operation is not supported
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* @throws ClassCastException if a key or value is of the wrong type
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* @throws IllegalArgumentException if something about a key or value
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* prevents it from existing in this map
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* @throws NullPointerException if the map forbids null keys or values, or
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* if <code>m</code> is null.
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* @see #put(Object, Object)
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*/
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public void putAll(Map m)
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{
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Iterator entries = m.entrySet().iterator();
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int pos = m.size();
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while (--pos >= 0)
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{
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Map.Entry entry = (Map.Entry) entries.next();
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put(entry.getKey(), entry.getValue());
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}
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}
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/**
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* Removes the mapping for this key if present (optional operation). This
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* implementation iterates over the entrySet searching for a matching
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* key, at which point it calls the iterator's <code>remove</code> method.
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* It returns the result of <code>getValue()</code> on the entry, if found,
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* or null if no entry is found. Note that maps which permit null values
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* may also return null if the key was removed. If the entrySet does not
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* support removal, this will also fail. This is O(n), so many
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* implementations override it for efficiency.
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*
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* @param key the key to remove
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* @return the value the key mapped to, or null if not present
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* @throws UnsupportedOperationException if deletion is unsupported
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* @see Iterator#remove()
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*/
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public Object remove(Object key)
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{
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Iterator entries = entrySet().iterator();
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int pos = size();
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while (--pos >= 0)
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{
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Map.Entry entry = (Map.Entry) entries.next();
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if (equals(key, entry.getKey()))
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{
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// Must get the value before we remove it from iterator.
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Object r = entry.getValue();
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entries.remove();
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return r;
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}
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}
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return null;
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}
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/**
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* Returns the number of key-value mappings in the map. If there are more
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* than Integer.MAX_VALUE mappings, return Integer.MAX_VALUE. This is
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* implemented as <code>entrySet().size()</code>.
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*
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* @return the number of mappings
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* @see Set#size()
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*/
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public int size()
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{
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return entrySet().size();
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}
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/**
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* Returns a String representation of this map. This is a listing of the
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* map entries (which are specified in Map.Entry as being
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* <code>getKey() + "=" + getValue()</code>), separated by a comma and
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* space (", "), and surrounded by braces ('{' and '}'). This implementation
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* uses a StringBuffer and iterates over the entrySet to build the String.
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* Note that this can fail with an exception if underlying keys or
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* values complete abruptly in toString().
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*
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* @return a String representation
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* @see Map.Entry#toString()
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*/
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public String toString()
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{
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Iterator entries = entrySet().iterator();
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StringBuffer r = new StringBuffer("{");
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for (int pos = size(); pos > 0; pos--)
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{
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Map.Entry entry = (Map.Entry) entries.next();
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r.append(entry.getKey());
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r.append('=');
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r.append(entry.getValue());
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if (pos > 1)
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r.append(", ");
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}
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r.append("}");
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return r.toString();
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}
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/**
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* Returns a collection or bag view of this map's values. The collection
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* is backed by the map, so changes in one show up in the other.
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* Modifications while an iteration is in progress produce undefined
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* behavior. The collection supports removal if entrySet() does, but
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* does not support element addition.
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* <p>
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*
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* This implementation creates an AbstractCollection, where the iterator
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* wraps the entrySet iterator, size defers to the Map's size, and contains
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* defers to the Map's containsValue. The collection is created on first
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* use, and returned on subsequent uses, although since no synchronization
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* occurs, there is a slight possibility of creating two collections.
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*
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* @return a Collection view of the values
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* @see Collection#iterator()
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* @see #size()
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* @see #containsValue(Object)
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* @see #keySet()
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*/
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public Collection values()
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{
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if (values == null)
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values = new AbstractCollection()
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{
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public int size()
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{
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return AbstractMap.this.size();
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}
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public Iterator iterator()
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{
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return new Iterator()
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{
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private final Iterator map_iterator = entrySet().iterator();
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public boolean hasNext()
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{
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return map_iterator.hasNext();
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}
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public Object next()
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{
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return ((Map.Entry) map_iterator.next()).getValue();
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}
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public void remove()
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{
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map_iterator.remove();
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}
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};
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}
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};
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return values;
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}
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/**
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* Compare two objects according to Collection semantics.
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*
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* @param o1 the first object
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* @param o2 the second object
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* @return o1 == null ? o2 == null : o1.equals(o2)
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*/
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// Package visible for use throughout java.util.
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// It may be inlined since it is final.
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static final boolean equals(Object o1, Object o2)
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{
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return o1 == null ? o2 == null : o1.equals(o2);
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}
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/**
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* Hash an object according to Collection semantics.
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*
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* @param o the object to hash
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* @return o1 == null ? 0 : o1.hashCode()
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*/
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// Package visible for use throughout java.util.
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// It may be inlined since it is final.
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static final int hashCode(Object o)
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{
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return o == null ? 0 : o.hashCode();
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}
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/**
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* A class which implements Map.Entry. It is shared by HashMap, TreeMap,
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* Hashtable, and Collections. It is not specified by the JDK, but makes
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* life much easier.
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*
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* @author Jon Zeppieri
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* @author Eric Blake <ebb9@email.byu.edu>
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*/
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static class BasicMapEntry implements Map.Entry
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{ // XXX - FIXME Use fully qualified implements as gcj 3.1 workaround.
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/**
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* The key. Package visible for direct manipulation.
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*/
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Object key;
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/**
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* The value. Package visible for direct manipulation.
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*/
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Object value;
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/**
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* Basic constructor initializes the fields.
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* @param newKey the key
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* @param newValue the value
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*/
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BasicMapEntry(Object newKey, Object newValue)
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{
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key = newKey;
|
|
value = newValue;
|
|
}
|
|
|
|
/**
|
|
* 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:
|
|
*
|
|
<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
|
|
*/
|
|
public final boolean equals(Object o)
|
|
{
|
|
if (! (o instanceof Map.Entry))
|
|
return false;
|
|
// Optimize for our own entries.
|
|
if (o instanceof BasicMapEntry)
|
|
{
|
|
BasicMapEntry e = (BasicMapEntry) o;
|
|
return (AbstractMap.equals(key, e.key)
|
|
&& AbstractMap.equals(value, e.value));
|
|
}
|
|
Map.Entry e = (Map.Entry) o;
|
|
return (AbstractMap.equals(key, e.getKey())
|
|
&& AbstractMap.equals(value, e.getValue()));
|
|
}
|
|
|
|
/**
|
|
* Get the key corresponding to this entry.
|
|
*
|
|
* @return the key
|
|
*/
|
|
public final Object getKey()
|
|
{
|
|
return key;
|
|
}
|
|
|
|
/**
|
|
* Get the value corresponding to this entry. If you already called
|
|
* Iterator.remove(), the behavior undefined, but in this case it works.
|
|
*
|
|
* @return the value
|
|
*/
|
|
public final Object getValue()
|
|
{
|
|
return 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 null). In other
|
|
* words, this must be:
|
|
*
|
|
<pre>(getKey() == null ? 0 : getKey().hashCode())
|
|
^ (getValue() == null ? 0 : getValue().hashCode())</pre>
|
|
*
|
|
* @return the hash code
|
|
*/
|
|
public final int hashCode()
|
|
{
|
|
return (AbstractMap.hashCode(key) ^ AbstractMap.hashCode(value));
|
|
}
|
|
|
|
/**
|
|
* Replaces the value with the specified object. This writes through
|
|
* to the map, unless you have already called Iterator.remove(). It
|
|
* may be overridden to restrict a null value.
|
|
*
|
|
* @param newVal the new value to store
|
|
* @return the old value
|
|
* @throws NullPointerException if the map forbids null values
|
|
*/
|
|
public Object setValue(Object newVal)
|
|
{
|
|
Object r = value;
|
|
value = newVal;
|
|
return r;
|
|
}
|
|
|
|
/**
|
|
* This provides a string representation of the entry. It is of the form
|
|
* "key=value", where string concatenation is used on key and value.
|
|
*
|
|
* @return the string representation
|
|
*/
|
|
public final String toString()
|
|
{
|
|
return key + "=" + value;
|
|
}
|
|
} // class BasicMapEntry
|
|
}
|