public WeakIdentityHashMap() 
{
		this.loadFactor = DEFAULT_LOAD_FACTOR;
		threshold = (int) ( DEFAULT_INITIAL_CAPACITY );
		table = new Entry[DEFAULT_INITIAL_CAPACITY];
}

Constructs a new, empty WeakIdentityHashMap with the default initial capacity (16) and the default load factor (0.75).

 public WeakIdentityHashMap(int initialCapacity) 
{
		this( initialCapacity, DEFAULT_LOAD_FACTOR );
}

Constructs a new, empty WeakIdentityHashMap with the given initial capacity and the default load factor, which is 0.75.

Parameters:

initialCapacity - The initial capacity of the WeakIdentityHashMap

Throws:

IllegalArgumentException - If the initial capacity is negative.

 public WeakIdentityHashMap(Map t) 
{
		this( Math.max( (int) ( t.size() / DEFAULT_LOAD_FACTOR ) + 1, 16 ),
				DEFAULT_LOAD_FACTOR );
		putAll( t );
}

Constructs a new WeakIdentityHashMap with the same mappings as the specified Map. The WeakIdentityHashMap is created with default load factor, which is 0.75 and an initial capacity sufficient to hold the mappings in the specified Map.

Parameters:

t - the map whose mappings are to be placed in this map.

Throws:

NullPointerException - if the specified map is null.

 public WeakIdentityHashMap(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 WeakIdentityHashMap with the given initial capacity and the given load factor.

Parameters:

initialCapacity - The initial capacity of the WeakIdentityHashMap

loadFactor - The load factor of the WeakIdentityHashMap

Throws:

IllegalArgumentException - If the initial capacity is negative, or if the load factor is nonpositive.

 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 )
			;
}

Removes all mappings from this map.

 public boolean containsKey(Object key) 
{
		return getEntry( key ) != null;
}

Returns true if this map contains a mapping for the specified key.

 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;
}

Returns true if this map maps one or more keys to the specified value.

 public Set entrySet() 
{
		Set< Map.Entry< K,V > > es = entrySet;
		return ( es != null ?
				es :
				( entrySet = new EntrySet() ) );
}

Returns a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry. 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 Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

 public V get(Object key) 
{
		Object k = maskNull( key );
		int h = hash( k );
		Entry< K,V >[] tab = getTable();
		int index = indexFor( h, tab.length );
		Entry< K,V > e = tab[index];
		while ( e != null ) {
			if ( e.hash == h && k == e.get() )
				return e.value;
			e = e.next;
		}
		return null;
}

Returns the value to which the specified key is mapped in this weak hash map, or null if the map contains no mapping for this key. A return value of null does not necessarily indicate that the map contains no mapping for the key; it is also possible that the map explicitly maps the key to null. The containsKey method may be used to distinguish these two cases.

 WeakIdentityHashMap.Entry getEntry(Object key) 
{
		Object k = maskNull( key );
		int h = hash( k );
		Entry< K,V >[] tab = getTable();
		int index = indexFor( h, tab.length );
		Entry< K,V > e = tab[index];
		while ( e != null && !( e.hash == h && k == e.get() ) )
			e = e.next;
		return e;
}

Returns the entry associated with the specified key in the HashMap. Returns null if the HashMap contains no mapping for this key.

 int hash(Object x) 
{
		int h = System.identityHashCode( x );
		return h - ( h < <  7 );  // that is,, -127 * h
}

Return a hash code for non-null Object x.

 static int indexFor(int h,
    int length) 
{
		return h & ( length - 1 );
}

Return index for hash code h.

 public boolean isEmpty() 
{
		return size() == 0;
}

Returns true 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 Set keySet() 
{
	                                                                           	 
		Set ks = keySet;
		return ( ks != null ?
				ks :
				( keySet = new KeySet() ) );
}

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 Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

 public V put(K key,
    V value) 
{
		K k = maskNull( key );
		int h = hash( k );
		Entry< K,V >[] tab = getTable();
		int i = indexFor( h, tab.length );
		for ( Entry< K,V > e = tab[i]; e != null; e = e.next ) {
			if ( h == e.hash && k == e.get() ) {
				V oldValue = e.value;
				if ( value != oldValue )
					e.value = value;
				return oldValue;
			}
		}
		modCount++;
		tab[i] = new Entry< K,V >( k, value, queue, h, tab[i] );
		if ( ++size  >= threshold )
			resize( tab.length * 2 );
		return null;
}

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.

 public  void putAll(Map t) 
{
		// Expand enough to hold t's elements without resizing.
		int n = t.size();
		if ( n == 0 )
			return;
		if ( n  >= threshold ) {
			n = (int) ( n / loadFactor + 1 );
			if ( n  > MAXIMUM_CAPACITY )
				n = MAXIMUM_CAPACITY;
			int capacity = table.length;
			while ( capacity <  n )
				capacity < < = 1;
			resize( capacity );
		}
		for ( Iterator i = t.entrySet().iterator(); i.hasNext(); ) {
			Map.Entry< K,V > e = (Map.Entry< K,V >) i.next(); //FIXME should not have to cast
			put( e.getKey(), e.getValue() );
		}
}

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.

 public V remove(Object key) 
{
		Object k = maskNull( key );
		int h = hash( k );
		Entry< K,V >[] tab = getTable();
		int i = indexFor( h, tab.length );
		Entry< K,V > prev = tab[i];
		Entry< K,V > e = prev;
		while ( e != null ) {
			Entry< K,V > next = e.next;
			if ( h == e.hash && k == e.get() ) {
				modCount++;
				size--;
				if ( prev == e )
					tab[i] = next;
				else
					prev.next = next;
				return e.value;
			}
			prev = e;
			e = next;
		}
		return null;
}

Removes the mapping for this key from this map if present.

 WeakIdentityHashMap.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;
}

Special version of remove needed by Entry set

 public boolean removeValue(Object value) 
{
		if ( value == null )
			return removeNullValue();
		Entry tab[] = getTable();
		Set keys = new HashSet();
		for ( int i = tab.length; i--  > 0; )
			for ( Entry e = tab[i]; e != null; e = e.next )
				if ( value.equals( e.value ) )
					keys.add( e.getKey() );
		for ( Object key : keys ) remove( key );
		return !keys.isEmpty();
}

Remove elements having the according value. Intended to avoid concurrent access exceptions It is expected that nobody add a key being removed by value

  void resize(int newCapacity) 
{
		// assert (newCapacity & -newCapacity) == newCapacity; // power of 2
		Entry< K,V >[] oldTable = getTable();
		int oldCapacity = oldTable.length;
		// check if needed
		if ( size <  threshold || oldCapacity  > newCapacity )
			return;
		Entry< K,V >[] 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;
		}
}

Rehashes the contents of this map into a new HashMap instance with a larger capacity. This method is called automatically when the number of keys in this map exceeds its capacity and load factor.

Note that this method is a no-op if it's called with newCapacity == 2*MAXIMUM_CAPACITY (which is Integer.MIN_VALUE).

 public int size() 
{
		if ( size == 0 )
			return 0;
		expungeStaleEntries();
		return size;
}

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 Collection values() 
{
		Collection vs = values;
		return ( vs != null ?
				vs :
				( values = new Values() ) );
}

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 Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.