A hashtable-based Map implementation with soft keys
/*
* Copyright 2006 (C) TJDO.
* All rights reserved.
*
* This software is distributed under the terms of the TJDO License version 1.0.
* See the terms of the TJDO License in the documentation provided with this software.
*
* $Id: SoftHashMap.java,v 1.2 2007/10/03 01:23:43 jackknifebarber Exp $
*/
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* A hashtable-based <tt>Map</tt> implementation with <em>soft keys</em>.
* An entry in a <tt>SoftHashMap</tt> will automatically be removed when
* its key is no longer in ordinary use.
* More precisely, the presence of a mapping for a given key will not prevent
* the key from being discarded by the garbage collector, that is, made
* finalizable, finalized, and then reclaimed.
* When a key has been discarded its entry is effectively removed from the map,
* so this class behaves somewhat differently than other <tt>Map</tt>
* implementations.
* <p>
* Both null values and the null key are supported. This class has performance
* characteristics similar to those of the <tt>HashMap</tt> class, and has the
* same efficiency parameters of <em>initial capacity</em> and <em>load
* factor</em>.
* <p>
* Like most collection classes, this class is not synchronized.
* A synchronized <tt>SoftHashMap</tt> may be constructed using the
* <tt>Collections.synchronizedMap</tt> method.
* <p>
* This class is intended primarily for use with key objects whose
* <tt>equals</tt> methods test for object identity using the <tt>==</tt>
* operator.
* Once such a key is discarded it can never be recreated, so it is impossible
* to do a lookup of that key in a <tt>SoftHashMap</tt> at some later time and
* be surprised that its entry has been removed.
* This class will work perfectly well with key objects whose <tt>equals</tt>
* methods are not based upon object identity, such as <tt>String</tt>
* instances.
* With such recreatable key objects, however, the automatic removal of
* <tt>SoftHashMap</tt> entries whose keys have been discarded may prove to be
* confusing.
* <p>
* The behavior of the <tt>SoftHashMap</tt> class depends in part upon the
* actions of the garbage collector, so several familiar (though not required)
* <tt>Map</tt> invariants do not hold for this class.
* Because the garbage collector may discard keys at any time, a
* <tt>SoftHashMap</tt> may behave as though an unknown thread is silently
* removing entries.s
* In particular, even if you synchronize on a <tt>SoftHashMap</tt> instance and
* invoke none of its mutator methods, it is possible for the <tt>size</tt>
* method to return smaller values over time, for the <tt>isEmpty</tt> method to
* return <tt>false</tt> and then <tt>true</tt>, for the <tt>containsKey</tt>
* method to return <tt>true</tt> and later <tt>false</tt> for a given key, for
* the <tt>get</tt> method to return a value for a given key but later return
* <tt>null</tt>, for the <tt>put</tt> method to return <tt>null</tt> and the
* <tt>remove</tt> method to return <tt>false</tt> for a key that previously
* appeared to be in the map, and for successive examinations of the key set,
* the value set, and the entry set to yield successively smaller numbers of
* elements.
* <p>
* Each key object in a <tt>SoftHashMap</tt> is stored indirectly as the
* referent of a soft reference.
* Therefore a key will automatically be removed only after the soft references
* to it, both inside and outside of the map, have been cleared by the garbage
* collector.
* <p>
* <strong>Implementation note:</strong> The value objects in a
* <tt>SoftHashMap</tt> are held by ordinary strong references.
* Thus care should be taken to ensure that value objects do not strongly refer
* to their own keys, either directly or indirectly, since that will prevent the
* keys from being discarded.
* Note that a value object may refer indirectly to its key via the
* <tt>SoftHashMap</tt> itself; that is, a value object may strongly refer to
* some other key object whose associated value object, in turn, strongly refers
* to the key of the first value object.
* One way to deal with this is to wrap values themselves within
* <tt>SoftReferences</tt> before inserting, as in: <tt>m.put(key, new
* SoftReference(value))</tt>, and then unwrapping upon each <tt>get</tt>.
* <p>
* The iterators returned by all of this class's "collection view methods" are
* <i>fail-fast</i>: if the map is structurally modified at any time after the
* iterator is created, in any way except through the iterator's own
* <tt>remove</tt> or <tt>add</tt> methods, the iterator will throw a
* <tt>ConcurrentModificationException</tt>.
* Thus, in the face of concurrent modification, the iterator fails quickly and
* cleanly, rather than risking arbitrary, non-deterministic behavior at an
* undetermined time in the future.
* <p>
* Note that the fail-fast behavior of an iterator cannot be guaranteed as it
* is, generally speaking, impossible to make any hard guarantees in the
* presence of unsynchronized concurrent modification.
* Fail-fast iterators throw <tt>ConcurrentModificationException</tt> on a
* best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: <i>the fail-fast behavior of iterators
* should be used only to detect bugs.</i>
*
* @author <a href="mailto:jackknifebarber@users.sourceforge.net">Mike Martin</a>
* (borrowing liberally from java.util.WeakHashMap)
* @version $Revision: 1.2 $
*/
public class SoftHashMap extends AbstractMap implements Map
{
/**
* The default initial capacity -- MUST be a power of two.
*/
private static final int DEFAULT_INITIAL_CAPACITY = 16;
/**
* The maximum capacity, used if a higher value is implicitly specified
* by either of the constructors with arguments.
* MUST be a power of two <= 1<<30.
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* The load fast used when none specified in constructor.
*/
private static final float DEFAULT_LOAD_FACTOR = 0.75f;
/**
* The table, resized as necessary. Length MUST Always be a power of two.
*/
private Entry[] table;
/**
* The number of key-value mappings contained in this soft hash map.
*/
private int size;
/**
* The next size value at which to resize (capacity * load factor).
*/
private int threshold;
/**
* The load factor for the hash table.
*/
private final float loadFactor;
/**
* Reference queue for cleared SoftEntries.
*/
private final ReferenceQueue queue = new ReferenceQueue();
/**
* The number of times this map has been structurally modified.
* Structural modifications are those that change the number of mappings or
* otherwise modify its internal structure (e.g., rehash).
* This field is used to make iterators on Collection-views of the map
* fail-fast.
* (See ConcurrentModificationException).
*/
private volatile int modCount;
/**
* Constructs a new, empty <tt>SoftHashMap</tt> with the given initial
* capacity and the given load factor.
*
* @param initialCapacity
* The initial capacity of the <tt>SoftHashMap</tt>
* @param loadFactor
* The load factor of the <tt>SoftHashMap</tt>
* @throws IllegalArgumentException
* If the initial capacity is negative, or if the load factor is
* nonpositive.
*/
public SoftHashMap(int initialCapacity, float loadFactor)
{
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal Initial Capacity: " + initialCapacity);
if (initialCapacity > MAXIMUM_CAPACITY)
initialCapacity = MAXIMUM_CAPACITY;
if (loadFactor <= 0 || Float.isNaN(loadFactor))
throw new IllegalArgumentException("Illegal Load factor: " + loadFactor);
int capacity = 1;
while (capacity < initialCapacity)
capacity <<= 1;
table = new Entry[capacity];
this.loadFactor = loadFactor;
threshold = (int)(capacity * loadFactor);
}
/**
* Constructs a new, empty <tt>SoftHashMap</tt> with the given initial
* capacity and the default load factor, which is <tt>0.75</tt>.
*
* @param initialCapacity
* The initial capacity of the <tt>SoftHashMap</tt>
* @throws IllegalArgumentException
* If the initial capacity is negative.
*/
public SoftHashMap(int initialCapacity)
{
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
/**
* Constructs a new, empty <tt>SoftHashMap</tt> with the default initial
* capacity (16) and the default load factor (0.75).
*/
public SoftHashMap()
{
loadFactor = DEFAULT_LOAD_FACTOR;
threshold = DEFAULT_INITIAL_CAPACITY;
table = new Entry[DEFAULT_INITIAL_CAPACITY];
}
/**
* Constructs a new <tt>SoftHashMap</tt> with the same mappings as the
* specified <tt>Map</tt>.
* The <tt>SoftHashMap</tt> is created with default load factor, which is
* <tt>0.75</tt> and an initial capacity sufficient to hold the mappings
* in the specified <tt>Map</tt>.
*
* @param t
* the map whose mappings are to be placed in this map.
* @throws NullPointerException
* if the specified map is null.
*/
public SoftHashMap(Map t)
{
this(Math.max((int)(t.size() / DEFAULT_LOAD_FACTOR) + 1, 16), DEFAULT_LOAD_FACTOR);
putAll(t);
}
// internal utilities
/**
* Value representing null keys inside tables.
*/
private static final Object NULL_KEY = new Object();
/**
* Use NULL_KEY for key if it is null.
*/
private static Object maskNull(Object key)
{
return key == null ? NULL_KEY : key;
}
/**
* Return internal representation of null key back to caller as null
*/
private static Object unmaskNull(Object key)
{
return key == NULL_KEY ? null : key;
}
/**
* Returns a hash value for the specified object.
* In addition to the object's own hashCode, this method applies a
* "supplemental hash function," which defends against poor quality hash
* functions.
* This is critical because HashMap uses power-of two length hash tables.
* <p>
* The shift distances in this function were chosen as the result of an
* automated search over the entire four-dimensional search space.
*/
static int hash(Object x)
{
int h = x.hashCode();
h += ~(h << 9);
h ^= (h >>> 14);
h += (h << 4);
h ^= (h >>> 10);
return h;
}
/**
* Check for equality of non-null reference x and possibly-null y.
* By default uses Object.equals.
*/
static boolean eq(Object x, Object y)
{
return x == y || x.equals(y);
}
/**
* Return index for hash code h.
*/
static int indexFor(int h, int length)
{
return h & (length - 1);
}
/**
* Expunge stale entries from the table.
*/
private void expungeStaleEntries()
{
Object r;
while ((r = queue.poll()) != null)
{
Entry e = (Entry)r;
int h = e.hash;
int i = indexFor(h, table.length);
Entry prev = table[i];
Entry p = prev;
while (p != null)
{
Entry next = p.next;
if (p == e)
{
if (prev == e)
table[i] = next;
else
prev.next = next;
e.next = null; // Help GC
e.value = null; // " "
size--;
break;
}
prev = p;
p = next;
}
}
}
/**
* Return the table after first expunging stale entries
*/
private Entry[] getTable()
{
expungeStaleEntries();
return table;
}
/**
* Returns the number of key-value mappings in this map.
* This result is a snapshot, and may not reflect unprocessed entries that
* will be removed before next attempted access because they are no longer
* referenced.
*/
public int size()
{
if (size == 0)
return 0;
expungeStaleEntries();
return size;
}
/**
* Returns <tt>true</tt> if this map contains no key-value mappings.
* This result is a snapshot, and may not reflect unprocessed entries that
* will be removed before next attempted access because they are no longer
* referenced.
*/
public boolean isEmpty()
{
return size() == 0;
}
/**
* Returns the value to which the specified key is mapped in this soft hash
* map, or <tt>null</tt> if the map contains no mapping for this key.
* A return value of <tt>null</tt> does not <i>necessarily</i> indicate that
* the map contains no mapping for the key; it is also possible that the map
* explicitly maps the key to <tt>null</tt>.
* The <tt>containsKey</tt> method may be used to distinguish these two
* cases.
*
* @param key
* the key whose associated value is to be returned.
* @return
* the value to which this map maps the specified key, or <tt>null</tt>
* if the map contains no mapping for this key.
*
* @see #put(Object, Object)
*/
public Object get(Object key)
{
Object k = maskNull(key);
int h = hash(k);
Entry[] tab = getTable();
int index = indexFor(h, tab.length);
Entry e = tab[index];
while (e != null)
{
if (e.hash == h && eq(k, e.get()))
return e.value;
e = e.next;
}
return null;
}
/**
* Returns <tt>true</tt> if this map contains a mapping for the specified
* key.
*
* @param key
* The key whose presence in this map is to be tested
* @return
* <tt>true</tt> if there is a mapping for <tt>key</tt>;
* <tt>false</tt> otherwise
*/
public boolean containsKey(Object key)
{
return getEntry(key) != null;
}
/**
* Returns the entry associated with the specified key in the map.
* Returns null if the map contains no mapping for this key.
*/
Entry getEntry(Object key)
{
Object k = maskNull(key);
int h = hash(k);
Entry[] tab = getTable();
int index = indexFor(h, tab.length);
Entry e = tab[index];
while (e != null && !(e.hash == h && eq(k, e.get())))
e = e.next;
return e;
}
/**
* Associates the specified value with the specified key in this map.
* If the map previously contained a mapping for this key, the old value is
* replaced.
*
* @param key
* key with which the specified value is to be associated.
* @param value
* value to be associated with the specified key.
* @return
* previous value associated with specified key, or <tt>null</tt> if
* there was no mapping for key. A <tt>null</tt> return can also
* indicate that the map previously associated <tt>null</tt> with the
* specified key.
*/
public Object put(Object key, Object value)
{
Object k = maskNull(key);
int h = hash(k);
Entry[] tab = getTable();
int i = indexFor(h, tab.length);
for (Entry e = tab[i]; e != null; e = e.next)
{
if (h == e.hash && eq(k, e.get()))
{
Object oldValue = e.value;
if (value != oldValue)
e.value = value;
return oldValue;
}
}
modCount++;
tab[i] = new Entry(k, value, queue, h, tab[i]);
if (++size >= threshold)
resize(tab.length * 2);
return null;
}
/**
* Rehashes the contents of this map into a new array with a
* larger capacity.
* This method is called automatically when the number of keys in this map
* reaches its threshold.
* <p>
* If current capacity is MAXIMUM_CAPACITY, this method does not resize the
* map, but but sets threshold to Integer.MAX_VALUE.
* This has the effect of preventing future calls.
*
* @param newCapacity
* the new capacity, MUST be a power of two; must be greater than
* current capacity unless current capacity is MAXIMUM_CAPACITY (in
* which case value is irrelevant).
*/
void resize(int newCapacity)
{
Entry[] oldTable = getTable();
int oldCapacity = oldTable.length;
if (oldCapacity == MAXIMUM_CAPACITY)
{
threshold = Integer.MAX_VALUE;
return;
}
Entry[] newTable = new Entry[newCapacity];
transfer(oldTable, newTable);
table = newTable;
/*
* If ignoring null elements and processing ref queue caused massive
* shrinkage, then restore old table. This should be rare, but avoids
* unbounded expansion of garbage-filled tables.
*/
if (size >= threshold / 2)
threshold = (int)(newCapacity * loadFactor);
else
{
expungeStaleEntries();
transfer(newTable, oldTable);
table = oldTable;
}
}
/** Transfer all entries from src to dest tables. */
private void transfer(Entry[] src, Entry[] dest)
{
for (int j = 0; j < src.length; ++j)
{
Entry e = src[j];
src[j] = null;
while (e != null)
{
Entry next = e.next;
Object key = e.get();
if (key == null)
{
e.next = null; // Help GC
e.value = null; // " "
size--;
}
else
{
int i = indexFor(e.hash, dest.length);
e.next = dest[i];
dest[i] = e;
}
e = next;
}
}
}
/**
* Copies all of the mappings from the specified map to this map.
* These mappings will replace any mappings that this map had for any of the
* keys currently in the specified map.
*
* @param m
* mappings to be stored in this map.
* @throws NullPointerException
* if the specified map is null.
*/
public void putAll(Map m)
{
int numKeysToBeAdded = m.size();
if (numKeysToBeAdded == 0)
return;
/*
* Expand the map if the map if the number of mappings to be added
* is greater than or equal to threshold. This is conservative; the
* obvious condition is (m.size() + size) >= threshold, but this
* condition could result in a map with twice the appropriate capacity,
* if the keys to be added overlap with the keys already in this map.
* By using the conservative calculation, we subject ourself
* to at most one extra resize.
*/
if (numKeysToBeAdded > threshold)
{
int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
if (targetCapacity > MAXIMUM_CAPACITY)
targetCapacity = MAXIMUM_CAPACITY;
int newCapacity = table.length;
while (newCapacity < targetCapacity)
newCapacity <<= 1;
if (newCapacity > table.length)
resize(newCapacity);
}
for (Iterator i = m.entrySet().iterator(); i.hasNext();)
{
Map.Entry e = (Map.Entry)i.next();
put(e.getKey(), e.getValue());
}
}
/**
* Removes the mapping for this key from this map if present.
*
* @param key
* key whose mapping is to be removed from the map.
* @return
* previous value associated with specified key, or <tt>null</tt> if
* there was no mapping for key. A <tt>null</tt> return can also
* indicate that the map previously associated <tt>null</tt> with the
* specified key.
*/
public Object remove(Object key)
{
Object k = maskNull(key);
int h = hash(k);
Entry[] tab = getTable();
int i = indexFor(h, tab.length);
Entry prev = tab[i];
Entry e = prev;
while (e != null)
{
Entry next = e.next;
if (h == e.hash && eq(k, e.get()))
{
modCount++;
size--;
if (prev == e)
tab[i] = next;
else
prev.next = next;
return e.value;
}
prev = e;
e = next;
}
return null;
}
/** Special version of remove needed by Entry set. */
Entry removeMapping(Object o)
{
if (!(o instanceof Map.Entry))
return null;
Entry[] tab = getTable();
Map.Entry entry = (Map.Entry)o;
Object k = maskNull(entry.getKey());
int h = hash(k);
int i = indexFor(h, tab.length);
Entry prev = tab[i];
Entry e = prev;
while (e != null)
{
Entry next = e.next;
if (h == e.hash && e.equals(entry))
{
modCount++;
size--;
if (prev == e)
tab[i] = next;
else
prev.next = next;
return e;
}
prev = e;
e = next;
}
return null;
}
/**
* Removes all mappings from this map.
*/
public void clear()
{
/*
* Clear out ref queue. We don't need to expunge entries since table
* is getting cleared.
*/
while (queue.poll() != null)
;
modCount++;
Entry tab[] = table;
for (int i = 0; i < tab.length; ++i)
tab[i] = null;
size = 0;
/*
* Allocation of array may have caused GC, which may have caused
* additional entries to go stale. Removing these entries from the
* reference queue will make them eligible for reclamation.
*/
while (queue.poll() != null)
;
}
/**
* Returns <tt>true</tt> if this map maps one or more keys to the specified
* value.
*
* @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.
*/
public boolean containsValue(Object value)
{
if (value == null)
return containsNullValue();
Entry tab[] = getTable();
for (int i = tab.length; i-- > 0;)
{
for (Entry e = tab[i]; e != null; e = e.next)
{
if (value.equals(e.value))
return true;
}
}
return false;
}
/**
* Special-case code for containsValue with null argument.
*/
private boolean containsNullValue()
{
Entry tab[] = getTable();
for (int i = tab.length; i-- > 0;)
{
for (Entry e = tab[i]; e != null; e = e.next)
{
if (e.value == null)
return true;
}
}
return false;
}
/**
* The entries in this hash table extend SoftReference, using its main ref
* field as the key.
*/
private static class Entry extends SoftReference implements Map.Entry
{
private Object value;
private final int hash;
private Entry next;
/**
* Create new entry.
*/
Entry(Object key, Object value, ReferenceQueue queue, int hash, Entry next)
{
super(key, queue);
this.value = value;
this.hash = hash;
this.next = next;
}
public Object getKey()
{
return unmaskNull(get());
}
public Object getValue()
{
return value;
}
public Object setValue(Object newValue)
{
Object oldValue = value;
value = newValue;
return oldValue;
}
public boolean equals(Object o)
{
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry)o;
Object k1 = getKey();
Object k2 = e.getKey();
if (k1 == k2 || (k1 != null && k1.equals(k2)))
{
Object v1 = getValue();
Object v2 = e.getValue();
if (v1 == v2 || (v1 != null && v1.equals(v2)))
return true;
}
return false;
}
public int hashCode()
{
Object k = getKey();
Object v = getValue();
return ((k==null ? 0 : k.hashCode()) ^
(v==null ? 0 : v.hashCode()));
}
public String toString()
{
return getKey() + "=" + getValue();
}
}
private abstract class HashIterator implements Iterator
{
int index;
Entry entry = null;
Entry lastReturned = null;
int expectedModCount = modCount;
/**
* Strong reference needed to avoid disappearance of key
* between hasNext and next
*/
Object nextKey = null;
/**
* Strong reference needed to avoid disappearance of key
* between nextEntry() and any use of the entry
*/
Object currentKey = null;
HashIterator()
{
index = (size() != 0 ? table.length : 0);
}
public boolean hasNext()
{
Entry[] t = table;
while (nextKey == null)
{
Entry e = entry;
int i = index;
while (e == null && i > 0)
e = t[--i];
entry = e;
index = i;
if (e == null)
{
currentKey = null;
return false;
}
nextKey = e.get(); // hold on to key in strong ref
if (nextKey == null)
entry = entry.next;
}
return true;
}
/** The common parts of next() across different types of iterators */
protected Entry nextEntry()
{
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
if (nextKey == null && !hasNext())
throw new NoSuchElementException();
lastReturned = entry;
entry = entry.next;
currentKey = nextKey;
nextKey = null;
return lastReturned;
}
public void remove()
{
if (lastReturned == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
SoftHashMap.this.remove(currentKey);
expectedModCount = modCount;
lastReturned = null;
currentKey = null;
}
}
private class ValueIterator extends HashIterator
{
public Object next()
{
return nextEntry().value;
}
}
private class KeyIterator extends HashIterator
{
public Object next()
{
return nextEntry().getKey();
}
}
private class EntryIterator extends HashIterator
{
public Object next()
{
return nextEntry();
}
}
// Views
private transient Set keySet = null;
private transient Collection values = null;
private transient Set entrySet = null;
/**
* Returns a 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.
* The set supports element removal, which removes the corresponding mapping
* from this 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.
*/
public Set keySet()
{
Set ks = keySet;
return (ks != null ? ks : (keySet = new KeySet()));
}
private class KeySet extends AbstractSet
{
public Iterator iterator()
{
return new KeyIterator();
}
public int size()
{
return SoftHashMap.this.size();
}
public boolean contains(Object o)
{
return containsKey(o);
}
public boolean remove(Object o)
{
if (containsKey(o))
{
SoftHashMap.this.remove(o);
return true;
}
else
return false;
}
public void clear()
{
SoftHashMap.this.clear();
}
public Object[] toArray()
{
Collection c = new ArrayList(size());
for (Iterator i = iterator(); i.hasNext(); )
c.add(i.next());
return c.toArray();
}
public Object[] toArray(Object a[])
{
Collection c = new ArrayList(size());
for (Iterator i = iterator(); i.hasNext(); )
c.add(i.next());
return c.toArray(a);
}
}
/**
* Returns a 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.
* The collection supports element removal, which removes the corresponding
* mapping from this 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.
*/
public Collection values()
{
Collection vs = values;
return (vs != null ? vs : (values = new Values()));
}
private class Values extends AbstractCollection
{
public Iterator iterator()
{
return new ValueIterator();
}
public int size()
{
return SoftHashMap.this.size();
}
public boolean contains(Object o)
{
return containsValue(o);
}
public void clear()
{
SoftHashMap.this.clear();
}
public Object[] toArray()
{
Collection c = new ArrayList(size());
for (Iterator i = iterator(); i.hasNext(); )
c.add(i.next());
return c.toArray();
}
public Object[] toArray(Object a[])
{
Collection c = new ArrayList(size());
for (Iterator i = iterator(); i.hasNext(); )
c.add(i.next());
return c.toArray(a);
}
}
/**
* Returns a collection view of the mappings contained in this map.
* Each element in the returned collection is a <tt>Map.Entry</tt>.
* The collection is backed by the map, so changes to the map are reflected
* in the collection, and vice-versa.
* 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 mappings contained in this map.
*/
public Set entrySet()
{
Set es = entrySet;
return (es != null ? es : (entrySet = new EntrySet()));
}
private class EntrySet extends AbstractSet
{
public Iterator iterator()
{
return new EntryIterator();
}
public boolean contains(Object o)
{
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry)o;
Entry candidate = getEntry(e.getKey());
return candidate != null && candidate.equals(e);
}
public boolean remove(Object o)
{
return removeMapping(o) != null;
}
public int size()
{
return SoftHashMap.this.size();
}
public void clear()
{
SoftHashMap.this.clear();
}
public Object[] toArray()
{
Collection c = new ArrayList(size());
for (Iterator i = iterator(); i.hasNext();)
c.add(new SimpleEntry((Map.Entry)i.next()));
return c.toArray();
}
public Object[] toArray(Object a[])
{
Collection c = new ArrayList(size());
for (Iterator i = iterator(); i.hasNext();)
c.add(new SimpleEntry((Map.Entry)i.next()));
return c.toArray(a);
}
}
static class SimpleEntry implements Map.Entry
{
private Object key;
private Object value;
public SimpleEntry(Map.Entry e)
{
this.key = e.getKey();
this.value = e.getValue();
}
public Object getKey()
{
return key;
}
public Object getValue()
{
return value;
}
public Object setValue(Object value)
{
Object oldValue = this.value;
this.value = value;
return oldValue;
}
public boolean equals(Object o)
{
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry)o;
return eq(key, e.getKey()) && eq(value, e.getValue());
}
public int hashCode()
{
return ((key == null) ? 0 : key.hashCode()) ^
((value == null) ? 0 : value.hashCode());
}
public String toString()
{
return key + "=" + value;
}
private static boolean eq(Object o1, Object o2)
{
return o1 == null ? o2 == null : o1.equals(o2);
}
}
}
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