/*******************************************************************************
* Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Gordon Yorke
******************************************************************************/
package org.eclipse.persistence.internal.helper;
/**
* INTERNAL:
* <p>
* <b>Purpose</b>: Define a {@link Map} that manages key equality by reference,
* not equals(). This is required to track objects throughout the lifecycle
* of a {@link org.eclipse.persistence.sessions.UnitOfWork}, regardless if the domain
* object redefines its equals() method. Additionally, this implementation does
* <b>not</b> permit nulls either as values or as keys. Any Entry that has a null in the key or
* in the value will be assumed to have garbage collected.
* This class also uses weak references to the contents of the map allowing for garbage
* collection to reduce the size of the Map
*
* This work is an extension of the original work completed on the IdentityWeakHashMap as completed by
* Mike Norman.
*
* @author Gordon Yorke (EclipseLink 1.0M4)
*
*/
// J2SE imports
import java.io.*;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.*;
import org.eclipse.persistence.internal.localization.ExceptionLocalization;
public class IdentityWeakHashMap<K,V> extends AbstractMap<K,V> implements Map<K,V>, Cloneable, Serializable {
static final long serialVersionUID = -5176951017503351630L;
// the default initial capacity
static final int DEFAULT_INITIAL_CAPACITY = 32;
// the maximum capacity.
static final int MAXIMUM_CAPACITY = 1 << 30;
// the loadFactor used when none specified in constructor.
static final float DEFAULT_LOAD_FACTOR = 0.75f;
protected transient WeakEntry<K,V>[] entries;// internal array of Entry's
protected transient int count = 0;
private transient int modCount = 0;// # of times this Map has been modified
protected int threshold = 0;
protected float loadFactor = 0;
/** This is used by the garbage collector. Every weak reference that is garbage collected
* will be enqueued on this. Then only this queue needs to be checked to remove empty
* references.
*/
protected ReferenceQueue referenceQueue;
/**
* Constructs a new <tt>IdentityWeakHashMap</tt> with the given
* initial capacity and the given loadFactor.
*
* @param initialCapacity the initial capacity of this
* <tt>IdentityWeakHashMap</tt>.
* @param loadFactor the loadFactor of the <tt>IdentityWeakHashMap</tt>.
* @throws IllegalArgumentException if the initial capacity is less
* than zero, or if the loadFactor is nonpositive.
*/
public IdentityWeakHashMap(int initialCapacity, float loadFactor) {
if (initialCapacity < 0) {
throw new IllegalArgumentException("Illegal initialCapacity: " + initialCapacity);
}
if (initialCapacity > MAXIMUM_CAPACITY) {
initialCapacity = MAXIMUM_CAPACITY;
}
if ((loadFactor <= 0) || Float.isNaN(loadFactor)) {
throw new IllegalArgumentException("Illegal loadFactor: " + loadFactor);
}
// Find a power of 2 >= initialCapacity
int capacity = 1;
while (capacity < initialCapacity) {
capacity <<= 1;
}
this.loadFactor = loadFactor;
threshold = (int)(capacity * loadFactor);
entries = new WeakEntry[capacity];
referenceQueue = new ReferenceQueue();
}
/**
* Constructs a new <tt>IdentityWeakHashMap</tt> with the given
* initial capacity and a default loadFactor of <tt>0.75</tt>.
*
* @param initialCapacity the initial capacity of the
* <tt>IdentityWeakHashMap</tt>.
* @throws <tt>IllegalArgumentException</tt> if the initial capacity is less
* than zero.
*/
public IdentityWeakHashMap(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
/**
* Constructs a new <tt>IdentityWeakHashMap</tt> with a default initial
* capacity of <tt>32</tt> and a loadfactor of <tt>0.75</tt>.
*/
public IdentityWeakHashMap() {
loadFactor = DEFAULT_LOAD_FACTOR;
threshold = (int)(DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
entries = new WeakEntry[DEFAULT_INITIAL_CAPACITY];
referenceQueue = new ReferenceQueue();
}
/**
* Constructs a new <tt>IdentityWeakHashMap</tt> with the same mappings
* as the given map. The <tt>IdentityWeakHashMap</tt> is created with a
* capacity sufficient to hold the elements of the given map.
*
* @param m the map whose mappings are to be placed in the
* <tt>IdentityWeakHashMap</tt>.
*/
public IdentityWeakHashMap(Map m) {
this(Math.max((int)(m.size() / DEFAULT_LOAD_FACTOR) + 1, DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
putAll(m);
}
/**
* @return the size of this <tt>IdentityWeakHashMap</tt>.
*/
public int size() {
cleanUp();
return count;
}
/**
* @return <tt>true</tt> if this <tt>IdentityWeakHashMap</tt> is empty.
*/
public boolean isEmpty() {
return (count == 0);
}
/**
* Returns <tt>true</tt> if this <tt>IdentityWeakHashMap</tt> contains
* the given object. Equality is tested by the equals() method.
*
* @param obj the object to find.
* @return <tt>true</tt> if this <tt>IdentityWeakHashMap</tt> contains
* obj.
* @throws <tt>NullPointerException</tt> if obj is null</tt>.
*/
public boolean containsValue(Object obj) {
if (obj == null) {
throw new IllegalArgumentException(ExceptionLocalization.buildMessage("null_not_supported_identityweakhashmap"));
}
//cleanup before searching as to reduce number of possible empty Entries
cleanUp();
WeakEntry<K,V>[] copyOfEntries = entries;
for (int i = copyOfEntries.length; i-- > 0;) {
for (WeakEntry<K,V> e = copyOfEntries[i]; e != null; e = e.next) {
if (obj.equals(e.value.get())) {
return true;
}
}
}
return false;
}
/**
* Returns <tt>true</tt> if this <tt>IdentityWeakHashMap</tt> contains a
* mapping for the given key. Equality is tested by reference.
*
* @param key object to be used as a key into this
* <tt>IdentityWeakHashMap</tt>.
* @return <tt>true</tt> if this <tt>IdentityWeakHashMap</tt> contains a
* mapping for key.
*/
public boolean containsKey(Object key) {
if (key == null) {
throw new IllegalArgumentException(ExceptionLocalization.buildMessage("null_not_supported_identityweakhashmap"));
}
cleanUp();
WeakEntry[] copyOfEntries = entries;
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (WeakEntry e = copyOfEntries[index]; e != null; e = e.next) {
if (e.key.get() == key) {
return true;
}
}
return false;
}
/**
* Returns the value to which the given key is mapped in this
* <tt>IdentityWeakHashMap</tt>. Returns <tt>null</tt> if this
* <tt>IdentityWeakHashMap</tt> contains no mapping for this key.
*
* @return the value to which this <tt>IdentityWeakHashMap</tt> maps the
* given key.
* @param key key whose associated value is to be returned.
*/
public V get(Object key) {
if (key == null) return null;
cleanUp();
WeakEntry[] copyOfEntries = entries;
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (WeakEntry e = copyOfEntries[index]; e != null; e = e.next) {
if (e.key.get() == key) {
return (V)e.value.get();
}
}
return null;
}
/**
* INTERNAL:
* Re-builds the internal array of Entry's with a larger capacity.
* This method is called automatically when the number of objects in this
* IdentityWeakHashMap exceeds its current threshold.
*/
private void rehash() {
int oldCapacity = entries.length;
WeakEntry[] oldEntries = entries;
int newCapacity = (oldCapacity * 2) + 1;
WeakEntry[] newEntries = new WeakEntry[newCapacity];
modCount++;
threshold = (int)(newCapacity * loadFactor);
entries = newEntries;
for (int i = oldCapacity; i-- > 0;) {
for (WeakEntry old = oldEntries[i]; old != null;) {
WeakEntry e = old;
old = old.next;
int index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = newEntries[index];
newEntries[index] = e;
}
}
}
/**
* Associate the given object with the given key in this
* <tt>IdentityWeakHashMap</tt>, replacing any existing mapping.
*
* @param key key to map to given object.
* @param obj object to be associated with key.
* @return the previous object for key or <tt>null</tt> if this
* <tt>IdentityWeakHashMap</tt> did not have one.
* @throws <tt>NullPointerException</tt> if obj is null</tt>.
*/
public V put(K key, V obj) {
if (obj == null || key == null) {
throw new IllegalArgumentException(ExceptionLocalization.buildMessage("null_not_supported_identityweakhashmap"));
}
cleanUp();
WeakEntry[] copyOfEntries = entries;
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (WeakEntry e = copyOfEntries[index]; e != null; e = e.next) {
if (e.key.get() == key) {
EntryReference<V> old = e.value;
if (key == obj){
e.value = e.key;
}else{
e.value = new HardEntryReference<V>(obj);
}
return old.get();
}
}
modCount++;
if (count >= threshold) {
rehash();
copyOfEntries = entries;
index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
}
WeakEntry<K,V> e = new WeakEntry<K,V>(hash, key, obj, copyOfEntries[index], referenceQueue);
copyOfEntries[index] = e;
count++;
return null;
}
/**
* Removes the mapping (key and its corresponding value) from this
* <tt>IdentityWeakHashMap</tt>, if present.
*
* @param key key whose mapping is to be removed from the map.
* @return the previous object for key or <tt>null</tt> if this
* <tt>IdentityWeakHashMap</tt> did not have one.
*/
public V remove(Object key) {
if (key == null) return null;
cleanUp();
WeakEntry[] copyOfEntries = entries;
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (WeakEntry e = copyOfEntries[index], prev = null; e != null; prev = e, e = e.next) {
if (e.key.get() == key) {
if (prev != null) {
prev.next = e.next;
} else {
copyOfEntries[index] = e.next;
}
count--;
return (V)e.value.get();
}
}
return null;
}
protected boolean removeEntry(WeakEntry o, boolean userModification) {
WeakEntry[] copyOfEntries = entries;
int index = (o.hash & 0x7FFFFFFF) % copyOfEntries.length;
for (WeakEntry e = copyOfEntries[index], prev = null; e != null;
prev = e, e = e.next) {
if (e == o) {
// if this method was called as a result of a user action,
// increment the modification count
// this method is also called by our cleanup code and
// that code should not cause a concurrent modification
// exception
if (userModification){
modCount++;
}
if (prev != null) {
prev.next = e.next;
} else {
copyOfEntries[index] = e.next;
}
count--;
e.value = null;
e.next = null;
return true;
}
}
return false;
}
/**
* Copies all of the mappings from the given map to this
* <tt>IdentityWeakHashMap</tt>, replacing any existing mappings.
*
* @param m mappings to be stored in this <tt>IdentityWeakHashMap</tt>.
* @throws <tt>NullPointerException</tt> if m is null.
*/
public void putAll(Map<? extends K, ? extends V> m) {
if (m == null) {
throw new NullPointerException();
}
Iterator<? extends Entry<? extends K, ? extends V>> i = m.entrySet().iterator();
while (i.hasNext()) {
Map.Entry<? extends K, ? extends V> me = i.next();
put(me.getKey(), me.getValue());
}
}
/**
* Removes all of the mappings from this <tt>IdentityWeakHashMap</tt>.
*/
public void clear() {
if (count > 0) {
modCount++;
WeakEntry[] copyOfEntries = entries;
for (int i = copyOfEntries.length; --i >= 0;) {
copyOfEntries[i] = null;
}
count = 0;
}
}
protected void cleanUp(){
WeakEntryReference reference = (WeakEntryReference)referenceQueue.poll();
while (reference != null){
// remove the entry but do not increment the modcount
// since this is not a user action
removeEntry(reference.owner, false);
reference = (WeakEntryReference)referenceQueue.poll();
}
}
/**
* Returns a shallow copy of this <tt>IdentityWeakHashMap</tt> (the
* elements are not cloned).
*
* @return a shallow copy of this <tt>IdentityWeakHashMap</tt>.
*/
public Object clone() {
try {
WeakEntry[] copyOfEntries = entries;
IdentityWeakHashMap clone = (IdentityWeakHashMap)super.clone();
clone.referenceQueue = new ReferenceQueue();
clone.entries = new WeakEntry[copyOfEntries.length];
for (int i = copyOfEntries.length; i-- > 0;) {
clone.entries[i] = (copyOfEntries[i] != null) ? (WeakEntry)copyOfEntries[i].clone(clone.referenceQueue) : null;
}
clone.keySet = null;
clone.entrySet = null;
clone.values = null;
clone.modCount = 0;
return clone;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
// Views - the following is standard 'boiler-plate' Map stuff
private transient Set keySet = null;
private transient Set entrySet = null;
private transient Collection values = null;
/**
* Returns a set view of the keys contained in this
* <tt>IdentityWeakHashMap</tt>. 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
* <tt>IdentityWeakHashMap</tt>.
*/
public Set keySet() {
if (keySet == null) {
keySet = new AbstractSet() {
public Iterator iterator() {
return getHashIterator(COMPONENT_TYPES.KEYS);
}
public int size() {
return count;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
int oldSize = count;
IdentityWeakHashMap.this.remove(o);
return count != oldSize;
}
public void clear() {
IdentityWeakHashMap.this.clear();
}
};
}
return keySet;
}
/**
* Returns a collection view of the values contained in this
* <tt>IdentityWeakHashMap</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 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
* <tt>IdentityWeakHashMap</tt>.
*/
public Collection values() {
if (values == null) {
values = new AbstractCollection() {
public Iterator iterator() {
return getHashIterator(COMPONENT_TYPES.VALUES);
}
public int size() {
return count;
}
public boolean contains(Object o) {
return containsValue(o);
}
public void clear() {
IdentityWeakHashMap.this.clear();
}
};
}
return values;
}
/**
* Returns a collection view of the mappings contained in this
* <tt>IdentityWeakHashMap</tt>. 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
* <tt>IdentityWeakHashMap</tt>.
*/
public Set entrySet() {
if (entrySet == null) {
entrySet = new AbstractSet() {
public Iterator iterator() {
return getHashIterator(COMPONENT_TYPES.ENTRIES);
}
public boolean contains(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
Map.Entry entry = (Map.Entry)o;
Object key = entry.getKey();
WeakEntry[] copyOfEntries = entries;
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (WeakEntry e = copyOfEntries[index]; e != null; e = e.next) {
if ((e.hash == hash) && e.equals(entry)) {
return true;
}
}
return false;
}
public boolean remove(Object o) {
if (!(o instanceof WeakEntry)) {
return false;
}
WeakEntry entry = (WeakEntry)o;
// remove the entry but and increment the modcount
// because this is a user action
return removeEntry(entry, true);
}
public int size() {
return count;
}
public void clear() {
IdentityWeakHashMap.this.clear();
}
};
}
return entrySet;
}
private Iterator getHashIterator(COMPONENT_TYPES type) {
if (count == 0) {
return emptyHashIterator;
} else {
return new HashIterator(type);
}
}
/**
* IdentityWeakHashMap entry.
*/
static class WeakEntry<K,V> implements Map.Entry<K,V> {
boolean removed = false;
int hash;
EntryReference<K> key;
EntryReference<V> value;
WeakEntry<K,V> next;
WeakEntry(int hash, K key, V value, WeakEntry<K,V> next, ReferenceQueue refQueue) {
this.hash = hash;
this.key = new WeakEntryReference<K>(key, refQueue, this);
if (key == value){
this.value = (EntryReference<V>)this.key;
}else{
this.value = new HardEntryReference<V>(value);
}
this.next = next;
}
protected Object clone(ReferenceQueue refQueue) {
WeakEntry current = this;
WeakEntry root = new WeakEntry(current.hash, current.key.get(), current.value.get(), null, refQueue);
WeakEntry currentClone = root;
while (current.next != null) {
currentClone.next = new WeakEntry(current.next.hash, current.next.key.get(), current.next.value.get(), null, refQueue);
current = current.next;
currentClone = currentClone.next;
}
return root;
}
// Map.Entry Ops
public K getKey() {
return key.get();
}
public V getValue() {
return value.get();
}
public V setValue(V value) {
EntryReference<V> oldValue = this.value;
if (value == this.key.get()){
this.value = (EntryReference<V>)this.key;
}else{
this.value = new HardEntryReference<V>(value);
}
return oldValue.get();
}
public boolean equals(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
Map.Entry e = (Map.Entry)o;
Object v = value.get();
return (key == e.getKey()) && ((v == null) ? (e.getValue() == null) : v.equals(e.getValue()));
}
public int hashCode() {
Object v = value.get();
return hash ^ ((v == null) ? 0 : v.hashCode());
}
public String toString() {
return key.get() + "=" + value.get();
}
public boolean shouldBeIgnored(){
return key.get() == null || value.get() == null;
}
}
static interface EntryReference<T> {
public T get();
}
static class WeakEntryReference<T> extends WeakReference<T> implements EntryReference{
protected WeakEntry owner;
protected boolean trashed = false;
protected ReferenceQueue referenceQueue;
public WeakEntryReference(T referent, ReferenceQueue<? super T> q, WeakEntry owner) {
super(referent, q);
this.owner = owner;
this.referenceQueue = q;
}
}
//This limited class is here to allow the value to be switched from a weak reference to a hard
// referernce. This Map only makes the key weak but inorder to allow for garbage collection
//of the key when the key and the value are the same object the same weak reference will be used
static class HardEntryReference<T> implements EntryReference{
protected T referent;
public HardEntryReference(T referent){
this.referent = referent;
}
public T get(){
return referent;
}
}
// Types of Iterators
private enum COMPONENT_TYPES {KEYS, VALUES, ENTRIES};
private static EmptyHashIterator emptyHashIterator = new EmptyHashIterator();
private static class EmptyHashIterator implements Iterator {
EmptyHashIterator() {
}
public boolean hasNext() {
return false;
}
public Object next() {
throw new NoSuchElementException();
}
public void remove() {
throw new IllegalStateException();
}
}
private class HashIterator implements Iterator {
WeakEntry[] entries = IdentityWeakHashMap.this.entries;
int index = entries.length;
WeakEntry entry = null;
WeakEntry lastReturned = null;
COMPONENT_TYPES type;
Object currentEntryRef;
/**
* The modCount value that the iterator believes that the backing
* List should have. If this expectation is violated, the iterator
* has detected concurrent modification.
*/
private int expectedModCount = modCount;
HashIterator(COMPONENT_TYPES type) {
this.type = type;
}
public boolean hasNext() {
WeakEntry e = entry;
int i = index;
WeakEntry[] copyOfEntries = IdentityWeakHashMap.this.entries;
while ((e == null || currentEntryRef == null) && (i > 0)) {
e = copyOfEntries[--i];
if (e != null) {
currentEntryRef = e.key.get();
}else{
currentEntryRef = null;
}
}
entry = e;
index = i;
return e != null && currentEntryRef != null;
}
public Object next() {
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
WeakEntry et = entry;
int i = index;
WeakEntry[] copyOfEntries = IdentityWeakHashMap.this.entries;
while ((et == null || currentEntryRef == null) && (i > 0)) {
et = copyOfEntries[--i];
if (et != null) {
currentEntryRef = et.key.get();
}else{
currentEntryRef = null;
}
}
entry = et;
index = i;
if (et != null) {
WeakEntry e = lastReturned = entry;
entry = e.next;
if (entry != null) {
currentEntryRef = entry.key.get();
}else{
currentEntryRef = null;
}
return (type == COMPONENT_TYPES.KEYS) ? e.key.get() : ((type == COMPONENT_TYPES.VALUES) ? e.value.get() : e);
}
throw new NoSuchElementException();
}
public void remove() {
if (lastReturned == null) {
throw new IllegalStateException();
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
WeakEntry[] copyOfEntries = IdentityWeakHashMap.this.entries;
int index = (lastReturned.hash & 0x7FFFFFFF) % copyOfEntries.length;
for (WeakEntry e = copyOfEntries[index], prev = null; e != null; prev = e, e = e.next) {
if (e == lastReturned) {
modCount++;
expectedModCount++;
if (prev == null) {
copyOfEntries[index] = e.next;
} else {
prev.next = e.next;
}
count--;
lastReturned = null;
return;
}
}
throw new ConcurrentModificationException();
}
}
/**
* Serialize the state of this <tt>IdentityWeakHashMap</tt> to a stream.
*
* @serialData The <i>capacity</i> of the <tt>IdentityWeakHashMap</tt>
* (the length of the bucket array) is emitted (int), followed by the
* <i>size</i> of the <tt>IdentityWeakHashMap</tt>, followed by the
* key-value mappings (in no particular order).
*/
private void writeObject(ObjectOutputStream s) throws IOException {
// Write out the threshold, loadfactor (and any hidden 'magic' stuff).
s.defaultWriteObject();
// Write out number of buckets
s.writeInt(entries.length);
// Write out count
s.writeInt(count);
// Write out contents
for (int i = entries.length - 1; i >= 0; i--) {
WeakEntry entry = entries[i];
while (entry != null) {
s.writeObject(entry.key.get());
s.writeObject(entry.value.get());
entry = entry.next;
}
}
}
/**
* Deserialize the <tt>IdentityWeakHashMap</tt> from a stream.
*/
private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
// Read in the threshold, loadfactor (and any hidden 'magic' stuff).
s.defaultReadObject();
// Read in number of buckets and allocate the bucket array;
int numBuckets = s.readInt();
entries = new WeakEntry[numBuckets];
// Read in size (count)
int size = s.readInt();
// Read the mappings and add to the IdentityWeakHashMap
for (int i = 0; i < size; i++) {
Object key = s.readObject();
Object value = s.readObject();
//only re-add if not null as could have been garbage collected at any time
//before the writeObject
if (key != null && value != null){
put((K)key, (V)value);
}
}
}
}