uk.org.retep.util.reference.DelayedWeakHashMap Maven / Gradle / Ivy
/*
* Copyright (c) 1998-2009, Peter T Mount
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of the retep.org.uk nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
*
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package uk.org.retep.util.reference;
import java.io.IOException;
import java.lang.ref.WeakReference;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import net.jcip.annotations.ThreadSafe;
import uk.org.retep.annotations.Contract;
import uk.org.retep.annotations.ReadLock;
import uk.org.retep.annotations.WriteLock;
/**
* A {@link Map} implementation who's values are stored using
* {@link java.lang.ref.WeakReference}'s. It's used where a key/value pair
* is to be stored but when the value is no longer referenced after a set period
* of time it is removed from memory.
*
* @param the type of keys maintained by this map
* @param the type of mapped values
* @author peter
* @since 9.6
*/
@ThreadSafe
public class DelayedWeakHashMap
extends AbstractMap
implements Map
{
private static final long DEFAULT_DELAY = 15000L;
private final ReadWriteLock lock = new ReentrantReadWriteLock();
private final long delay;
static final int DEFAULT_INITIAL_CAPACITY = 16;
static final int MAXIMUM_CAPACITY = 1 << 30;
static final float DEFAULT_LOAD_FACTOR = 0.75f;
transient Entry[] table;
transient int size;
int threshold;
final float loadFactor;
transient volatile int modCount;
protected KeySet keySet;
protected Values values;
public DelayedWeakHashMap()
{
this( DEFAULT_DELAY );
}
public DelayedWeakHashMap( final Map map )
{
this( DEFAULT_DELAY, map );
}
public DelayedWeakHashMap( final int initialCapacity )
{
this( DEFAULT_DELAY, initialCapacity );
}
public DelayedWeakHashMap( final int initialCapacity, final float loadFactor )
{
this( DEFAULT_DELAY, initialCapacity, loadFactor );
}
public DelayedWeakHashMap( final long delay, final int initialCapacity )
{
this( DEFAULT_DELAY, initialCapacity, DEFAULT_LOAD_FACTOR );
}
public DelayedWeakHashMap( final long delay )
{
this.delay = delay;
this.loadFactor = DEFAULT_LOAD_FACTOR;
threshold = (int) (DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
table = new Entry[ DEFAULT_INITIAL_CAPACITY ];
init();
}
public DelayedWeakHashMap( final long delay,
int initialCapacity,
float loadFactor )
{
this.delay = delay;
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 );
}
// Find a power of 2 >= initialCapacity
int capacity = 1;
while( capacity < initialCapacity )
{
capacity <<= 1;
}
this.loadFactor = loadFactor;
threshold = (int) (capacity * loadFactor);
table = new Entry[ capacity ];
init();
}
public DelayedWeakHashMap( final long delay, Map m )
{
this( delay,
Math.max( (int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
DEFAULT_INITIAL_CAPACITY ), DEFAULT_LOAD_FACTOR );
putAllForCreate( m );
}
/**
* Used for concurrency
* @return
*/
@Contract( ReadLock.class )
protected final java.util.concurrent.locks.Lock readLock()
{
return lock.readLock();
}
/**
* Used for concurrency
* @return
*/
@Contract( WriteLock.class )
protected final java.util.concurrent.locks.Lock writeLock()
{
return lock.writeLock();
}
/**
* Initialization hook for subclasses. This method is called
* in all constructors and pseudo-constructors (clone, readObject)
* after HashMap has been initialized but before any entries have
* been inserted. (In the absence of this method, readObject would
* require explicit knowledge of subclasses.)
*/
protected void init()
{
}
/**
* Applies a supplemental hash function to a given hashCode, which
* defends against poor quality hash functions. This is critical
* because HashMap uses power-of-two length hash tables, that
* otherwise encounter collisions for hashCodes that do not differ
* in lower bits. Note: Null keys always map to hash 0, thus index 0.
*/
static int hash( int h )
{
// This function ensures that hashCodes that differ only by
// constant multiples at each bit position have a bounded
// number of collisions (approximately 8 at default load factor).
h ^= (h >>> 20) ^ (h >>> 12);
return h ^ (h >>> 7) ^ (h >>> 4);
}
/**
* Returns index for hash code h.
*/
static int indexFor( int h, int length )
{
return h & (length - 1);
}
/**
* Returns the number of key-value mappings in this map.
*
* @return the number of key-value mappings in this map
*/
@ReadLock
@Override
public int size()
{
return size;
}
/**
* Returns true if this map contains no key-value mappings.
*
* @return true if this map contains no key-value mappings
*/
@ReadLock
@Override
public boolean isEmpty()
{
return size == 0;
}
/**
* Returns the value to which the specified key is mapped,
* or {@code null} if this map contains no mapping for the key.
*
* More formally, if this map contains a mapping from a key
* {@code k} to a value {@code v} such that {@code (key==null ? k==null :
* key.equals(k))}, then this method returns {@code v}; otherwise
* it returns {@code null}. (There can be at most one such mapping.)
*
*
A return value of {@code null} does not necessarily
* indicate that the map contains no mapping for the key; it's also
* possible that the map explicitly maps the key to {@code null}.
* The {@link #containsKey containsKey} operation may be used to
* distinguish these two cases.
*
* @see #put(Object, Object)
*/
@ReadLock
@Override
public V get( Object key )
{
if( key == null )
{
return getForNullKey();
}
int hash = hash( key.hashCode() );
for( Entry e = table[indexFor( hash, table.length )];
e != null;
e = e.next )
{
Object k;
if( e.hash == hash && ((k = e.key) == key || key.equals( k )) )
{
return e.getValue();
}
}
return null;
}
/**
* Offloaded version of get() to look up null keys. Null keys map
* to index 0. This null case is split out into separate methods
* for the sake of performance in the two most commonly used
* operations (get and put), but incorporated with conditionals in
* others.
*/
private V getForNullKey()
{
for( Entry e = table[0]; e != null; e = e.next )
{
if( e.key == null )
{
return e.getValue();
}
}
return null;
}
/**
* Returns true if this map contains a mapping for the
* specified key.
*
* @param key The key whose presence in this map is to be tested
* @return true if this map contains a mapping for the specified
* key.
*/
@ReadLock
@Override
public boolean containsKey( Object key )
{
return getEntry( key ) != null;
}
/**
* Returns the entry associated with the specified key in the
* HashMap. Returns null if the HashMap contains no mapping
* for the key.
*/
@ReadLock
final Entry getEntry( Object key )
{
int hash = (key == null) ? 0 : hash( key.hashCode() );
for( Entry e = table[indexFor( hash, table.length )];
e != null;
e = e.next )
{
Object k;
if( e.hash == hash &&
((k = e.key) == key || (key != null && key.equals( k ))) )
{
return e;
}
}
return null;
}
/**
* Associates the specified value with the specified key in this map.
* If the map previously contained a mapping for the 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 the previous value associated with key, or
* null if there was no mapping for key.
* (A null return can also indicate that the map
* previously associated null with key.)
*/
@WriteLock
@Override
public V put( K key, V value )
{
if( key == null )
{
return putForNullKey( value );
}
int hash = hash( key.hashCode() );
int i = indexFor( hash, table.length );
for( Entry e = table[i]; e != null; e = e.next )
{
Object k;
if( e.hash == hash && ((k = e.key) == key || key.equals( k )) )
{
V oldValue = e.setValue( value );
e.recordAccess( this );
return oldValue;
}
}
modCount++;
addEntry( hash, key, value, i );
return null;
}
/**
* Offloaded version of put for null keys
*/
private V putForNullKey( V value )
{
for( Entry e = table[0]; e != null; e = e.next )
{
if( e.key == null )
{
V oldValue = e.setValue( value );
e.recordAccess( this );
return oldValue;
}
}
modCount++;
addEntry( 0, null, value, 0 );
return null;
}
/**
* This method is used instead of put by constructors and
* pseudoconstructors (clone, readObject). It does not resize the table,
* check for comodification, etc. It calls createEntry rather than
* addEntry.
*/
private void putForCreate( K key, V value )
{
int hash = (key == null) ? 0 : hash( key.hashCode() );
int i = indexFor( hash, table.length );
/**
* Look for preexisting entry for key. This will never happen for
* clone or deserialize. It will only happen for construction if the
* input Map is a sorted map whose ordering is inconsistent w/ equals.
*/
for( Entry e = table[i]; e != null; e = e.next )
{
Object k;
if( e.hash == hash &&
((k = e.key) == key || (key != null && key.equals( k ))) )
{
e.setValue( value );
return;
}
}
createEntry( hash, key, value, i );
}
private void putAllForCreate( Map m )
{
for( Iterator> i = m.entrySet().iterator(); i.hasNext(); )
{
Map.Entry e = i.next();
putForCreate( e.getKey(), e.getValue() );
}
}
/**
* 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.
*
* If current capacity is MAXIMUM_CAPACITY, this method does not
* resize the map, 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 = table;
int oldCapacity = oldTable.length;
if( oldCapacity == MAXIMUM_CAPACITY )
{
threshold = Integer.MAX_VALUE;
return;
}
Entry[] newTable = new Entry[ newCapacity ];
transfer( newTable );
table = newTable;
threshold = (int) (newCapacity * loadFactor);
}
/**
* Transfers all entries from current table to newTable.
*/
void transfer( Entry[] newTable )
{
Entry[] src = table;
int newCapacity = newTable.length;
for( int j = 0; j < src.length; j++ )
{
Entry e = src[j];
if( e != null )
{
src[j] = null;
do
{
Entry next = e.next;
int i = indexFor( e.hash, newCapacity );
e.next = newTable[i];
newTable[i] = e;
e = next;
} while( e != null );
}
}
}
/**
* 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
*/
@WriteLock
@Override
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 = i.next();
put( e.getKey(), e.getValue() );
}
}
/**
* Removes the mapping for the specified key from this map if present.
*
* @param key key whose mapping is to be removed from the map
* @return the previous value associated with key, or
* null if there was no mapping for key.
* (A null return can also indicate that the map
* previously associated null with key.)
*/
@WriteLock
@Override
public V remove( Object key )
{
Entry e = removeEntryForKey( key );
return (e == null ? null : e.getValue());
}
/**
* Removes and returns the entry associated with the specified key
* in the HashMap. Returns null if the HashMap contains no mapping
* for this key.
*/
@WriteLock
final Entry removeEntryForKey( Object key )
{
int hash = (key == null) ? 0 : hash( key.hashCode() );
int i = indexFor( hash, table.length );
Entry prev = table[i];
Entry e = prev;
while( e != null )
{
Entry next = e.next;
Object k;
if( e.hash == hash &&
((k = e.key) == key || (key != null && key.equals( k ))) )
{
modCount++;
size--;
if( prev == e )
{
table[i] = next;
}
else
{
prev.next = next;
}
e.recordRemoval( this );
return e;
}
prev = e;
e = next;
}
return e;
}
/**
* Special version of remove for EntrySet.
*/
final Entry removeMapping( Object o )
{
if( !(o instanceof Map.Entry) )
{
return null;
}
Map.Entry entry = (Map.Entry) o;
Object key = entry.getKey();
int hash = (key == null) ? 0 : hash( key.hashCode() );
int i = indexFor( hash, table.length );
Entry prev = table[i];
Entry e = prev;
while( e != null )
{
Entry next = e.next;
if( e.hash == hash && e.equals( entry ) )
{
modCount++;
size--;
if( prev == e )
{
table[i] = next;
}
else
{
prev.next = next;
}
e.recordRemoval( this );
return e;
}
prev = e;
e = next;
}
return e;
}
/**
* Removes all of the mappings from this map.
* The map will be empty after this call returns.
*/
@WriteLock
@Override
public void clear()
{
modCount++;
Entry[] tab = table;
for( int i = 0; i < tab.length; i++ )
{
tab[i] = null;
}
size = 0;
}
/**
* Returns true 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 true if this map maps one or more keys to the
* specified value
*/
@ReadLock
public boolean containsValue( Object value )
{
if( value == null )
{
return containsNullValue();
}
Entry[] tab = table;
for( int i = 0; i < tab.length; i++ )
{
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 = table;
for( int i = 0; i < tab.length; i++ )
{
for( Entry e = tab[i]; e != null; e = e.next )
{
if( e.value == null )
{
return true;
}
}
}
return false;
}
/**
* Returns a shallow copy of this HashMap instance: the keys and
* values themselves are not cloned.
*
* @return a shallow copy of this map
*/
@ReadLock
public Object clone()
{
DelayedWeakHashMap result = null;
try
{
result = (DelayedWeakHashMap) super.clone();
}
catch( CloneNotSupportedException e )
{
// assert false;
}
result.table = new Entry[ table.length ];
result.entrySet = null;
result.modCount = 0;
result.size = 0;
result.init();
result.putAllForCreate( this );
return result;
}
/**
* The delay that an Entry will remain in the map after it's last access
* until it is removed from the Map
* @return delay in milliseconds
*/
public final long getDelay()
{
return delay;
}
class Ref
extends AbstractDelayedWeakReference
{
private final K key;
public Ref( final K key, final V v )
{
super( getDelay(), v );
this.key = key;
}
@Override
protected void remove( final V o )
{
DelayedWeakHashMap.this.removeEntryForKey( key );
}
@Override
public String toString()
{
return key == null ? null : key.toString();
}
}
@ThreadSafe
class Entry
implements Map.Entry
{
final K key;
Ref value;
Entry next;
final int hash;
/**
* Creates new entry.
*/
Entry( int h, K k, V v, Entry n )
{
value = new Ref( k, v );
next = n;
key = k;
hash = h;
}
@Contract( ReadLock.class )
protected final java.util.concurrent.locks.Lock readLock()
{
return DelayedWeakHashMap.this.readLock();
}
@Contract( WriteLock.class )
protected final java.util.concurrent.locks.Lock writeLock()
{
return DelayedWeakHashMap.this.writeLock();
}
@ReadLock
@Override
public final K getKey()
{
return key;
}
@ReadLock
@Override
public final V getValue()
{
return value.get();
}
@WriteLock
@Override
public final V setValue( V newValue )
{
final V oldValue = value.getAndRelease();
value = new Ref( key, newValue );
return oldValue;
}
@Override
public final 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;
}
@Override
public final int hashCode()
{
return (key == null ? 0 : key.hashCode()) ^
(value == null ? 0 : value.getHashCode());
}
@Override
public final String toString()
{
return getKey() + "=" + getValue();
}
/**
* This method is invoked whenever the value in an entry is
* overwritten by an invocation of put(k,v) for a key k that's already
* in the HashMap.
*/
void recordAccess( DelayedWeakHashMap m )
{
}
/**
* This method is invoked whenever the entry is
* removed from the table.
*/
void recordRemoval( DelayedWeakHashMap m )
{
// Tell the gc that we are no longer managing the value
value.getAndRelease();
value = null;
}
}
/**
* Adds a new entry with the specified key, value and hash code to
* the specified bucket. It is the responsibility of this
* method to resize the table if appropriate.
*
* Subclass overrides this to alter the behavior of put method.
*/
void addEntry( int hash, K key, V value, int bucketIndex )
{
Entry e = table[bucketIndex];
table[bucketIndex] = new Entry( hash, key, value, e );
if( size++ >= threshold )
{
resize( 2 * table.length );
}
}
/**
* Like addEntry except that this version is used when creating entries
* as part of Map construction or "pseudo-construction" (cloning,
* deserialization). This version needn't worry about resizing the table.
*
* Subclass overrides this to alter the behavior of HashMap(Map),
* clone, and readObject.
*/
void createEntry( int hash, K key, V value, int bucketIndex )
{
Entry e = table[bucketIndex];
table[bucketIndex] = new Entry( hash, key, value, e );
size++;
}
private abstract class HashIterator
implements Iterator
{
Entry next; // next entry to return
int expectedModCount; // For fast-fail
int index; // current slot
Entry current; // current entry
HashIterator()
{
expectedModCount = modCount;
if( size > 0 )
{ // advance to first entry
Entry[] t = table;
while( index < t.length && (next = t[index++]) == null );
}
}
@Override
public final boolean hasNext()
{
return next != null;
}
@SuppressWarnings( "empty-statement" )
final Entry nextEntry()
{
if( modCount != expectedModCount )
{
throw new ConcurrentModificationException();
}
Entry e = next;
if( e == null )
{
throw new NoSuchElementException();
}
if( (next = e.next) == null )
{
Entry[] t = table;
while( index < t.length && (next = t[index++]) == null );
}
current = e;
return e;
}
@Override
public void remove()
{
if( current == null )
{
throw new IllegalStateException();
}
if( modCount != expectedModCount )
{
throw new ConcurrentModificationException();
}
Object k = current.key;
current = null;
DelayedWeakHashMap.this.removeEntryForKey( k );
expectedModCount = modCount;
}
}
private final class ValueIterator
extends HashIterator
{
@Override
public V next()
{
return nextEntry().getValue();
}
}
private final class KeyIterator
extends HashIterator
{
public K next()
{
return nextEntry().getKey();
}
}
private final class EntryIterator
extends HashIterator>
{
@Override
public Map.Entry next()
{
return nextEntry();
}
}
// Subclass overrides these to alter behavior of views' iterator() method
Iterator newKeyIterator()
{
return new KeyIterator();
}
Iterator newValueIterator()
{
return new ValueIterator();
}
Iterator> newEntryIterator()
{
return new EntryIterator();
}
// Views
private transient Set> entrySet = null;
/**
* Returns a {@link 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. If the map is modified
* while an iteration over the set is in progress (except through
* the iterator's own remove operation), the results of
* the iteration are undefined. The set supports element removal,
* which removes the corresponding mapping from the map, via the
* Iterator.remove, Set.remove,
* removeAll, retainAll, and clear
* operations. It does not support the add or addAll
* operations.
*/
@Override
@WriteLock
public Set keySet()
{
Set ks = keySet;
return (ks != null ? ks : (keySet = new KeySet()));
}
@ThreadSafe
private final class KeySet
extends AbstractSet
{
@Contract( ReadLock.class )
protected final java.util.concurrent.locks.Lock readLock()
{
return DelayedWeakHashMap.this.readLock();
}
@Contract( WriteLock.class )
protected final java.util.concurrent.locks.Lock writeLock()
{
return DelayedWeakHashMap.this.writeLock();
}
@Override
@ReadLock
public Iterator iterator()
{
return newKeyIterator();
}
@Override
@ReadLock
public int size()
{
return size;
}
@Override
public boolean contains( Object o )
{
return containsKey( o );
}
@Override
@WriteLock
public boolean remove( Object o )
{
return DelayedWeakHashMap.this.removeEntryForKey( o ) != null;
}
@Override
public void clear()
{
DelayedWeakHashMap.this.clear();
}
}
/**
* Returns a {@link 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. If the map is
* modified while an iteration over the collection is in progress
* (except through the iterator's own remove operation),
* the results of the iteration are undefined. 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.
*/
@Override
@WriteLock
public Collection values()
{
Collection vs = values;
return (vs != null ? vs : (values = new Values()));
}
@ThreadSafe
private final class Values
extends AbstractCollection
{
@Contract( ReadLock.class )
protected final java.util.concurrent.locks.Lock readLock()
{
return DelayedWeakHashMap.this.readLock();
}
@Contract( WriteLock.class )
protected final java.util.concurrent.locks.Lock writeLock()
{
return DelayedWeakHashMap.this.writeLock();
}
@ReadLock
public Iterator iterator()
{
return newValueIterator();
}
@Override
@ReadLock
public int size()
{
return size;
}
@Override
public boolean contains( Object o )
{
return containsValue( o );
}
@Override
public void clear()
{
DelayedWeakHashMap.this.clear();
}
}
/**
* Returns a {@link Set} view of the mappings contained in this map.
* The set is backed by the map, so changes to the map are
* reflected in the set, and vice-versa. If the map is modified
* while an iteration over the set is in progress (except through
* the iterator's own remove operation, or through the
* setValue operation on a map entry returned by the
* iterator) the results of the iteration are undefined. The set
* supports element removal, which removes the corresponding
* mapping from the map, via the Iterator.remove,
* Set.remove, removeAll, retainAll and
* clear operations. It does not support the
* add or addAll operations.
*
* @return a set view of the mappings contained in this map
*/
@Override
public Set> entrySet()
{
return entrySet0();
}
@WriteLock
private Set> entrySet0()
{
Set> es = entrySet;
return es != null ? es : (entrySet = new EntrySet());
}
@ThreadSafe
private final class EntrySet
extends AbstractSet>
{
@Contract( ReadLock.class )
protected final java.util.concurrent.locks.Lock readLock()
{
return DelayedWeakHashMap.this.readLock();
}
@Contract( WriteLock.class )
protected final java.util.concurrent.locks.Lock writeLock()
{
return DelayedWeakHashMap.this.writeLock();
}
@Override
public Iterator> iterator()
{
return newEntryIterator();
}
@Override
@ReadLock
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 );
}
@Override
@WriteLock
public boolean remove( Object o )
{
return removeMapping( o ) != null;
}
@Override
@ReadLock
public int size()
{
return size;
}
@Override
public void clear()
{
DelayedWeakHashMap.this.clear();
}
}
/**
* Save the state of the HashMap instance to a stream (i.e.,
* serialize it).
*
* We don't actually store the contents as it's weak.
*/
private void writeObject( java.io.ObjectOutputStream s )
throws IOException
{
Iterator> i =
(size > 0) ? entrySet0().iterator() : null;
// Write out the threshold, loadfactor, and any hidden stuff
s.defaultWriteObject();
}
private static final long serialVersionUID = 362498820763181265L;
/**
* Reconstitute the HashMap instance from a stream (i.e.,
* deserialize it).
*/
private void readObject( java.io.ObjectInputStream s )
throws IOException,
ClassNotFoundException
{
// Read in the threshold, loadfactor, and any hidden stuff
s.defaultReadObject();
table = new Entry[ DEFAULT_INITIAL_CAPACITY ];
init(); // Give subclass a chance to do its thing.
size = 0;
}
float loadFactor()
{
return loadFactor;
}
}