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Added some lock-free concurrent collections (set, map, bi-map)

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nathan 2018-01-25 16:38:54 +01:00
parent ff502785fd
commit 19c9ae67ee
3 changed files with 815 additions and 0 deletions
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412
src/dorkbox/util/collections/LockFreeBiMap.java Normal file
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/*
* Copyright 2018 dorkbox, llc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package dorkbox.util.collections;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
/**
* A bimap (or "bidirectional map") is a map that preserves the uniqueness of its values as well as that of its keys. This constraint
* enables bimaps to support an "inverse view", which is another bimap containing the same entries as this bimap but with reversed keys and values.
*
* This class uses the "single-writer-principle" for lock-free publication.
*
* Since there are only 2 methods to guarantee that modifications can only be called one-at-a-time (either it is only called by
* one thread, or only one thread can access it at a time) -- we chose the 2nd option -- and use 'synchronized' to make sure that only
* one thread can access this modification methods at a time. Getting or checking the presence of values can then happen in a lock-free
* manner.
*
* According to my benchmarks, this is approximately 25% faster than ConcurrentHashMap for (all types of) reads, and a lot slower for
* contended writes.
*
* This data structure is for many-read/few-write scenarios
*/
public final
class LockFreeBiMap<K, V> {
// Recommended for best performance while adhering to the "single writer principle". Must be static-final
private static final AtomicReferenceFieldUpdater<LockFreeBiMap, HashMap> forwardREF =
AtomicReferenceFieldUpdater.newUpdater(LockFreeBiMap.class,
HashMap.class,
"forwardHashMap");
private static final AtomicReferenceFieldUpdater<LockFreeBiMap, HashMap> reverseREF =
AtomicReferenceFieldUpdater.newUpdater(LockFreeBiMap.class,
HashMap.class,
"reverseHashMap");
private volatile HashMap<K, V> forwardHashMap = new HashMap<K, V>();
private volatile HashMap<V, K> reverseHashMap = new HashMap<V, K>();
// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
// use-case 99% of the time)
public
LockFreeBiMap() {
}
/**
* Removes all of the mappings from this bimap.
* The bimap will be empty after this call returns.
*/
public synchronized
void clear() {
forwardHashMap.clear();
reverseHashMap.clear();
}
/**
* Replaces all of the mappings from the specified map to this bimap.
* These mappings will replace any mappings that this map had for
* any of the keys currently in the specified map.
*
* @param hashMap mappings to be stored in this map
*
* @throws NullPointerException if the specified map is null
*
* @throws IllegalArgumentException if a given value in the map is already bound to a different key in this bimap. The bimap will remain
* unmodified in this event. To avoid this exception, call {@link #replaceAllForce(Map)} replaceAllForce(map) instead.
*/
public synchronized
void replaceAll(final Map<K, V> hashMap) throws IllegalArgumentException {
if (hashMap == null) {
throw new NullPointerException("hashMap");
}
LockFreeBiMap<K, V> biMap = new LockFreeBiMap<K, V>();
try {
biMap.putAll(hashMap);
} catch (IllegalArgumentException e) {
// do nothing if there is an exception
throw e;
}
// only if there are no problems with the creation of the new bimap.
this.forwardHashMap.clear();
this.reverseHashMap.clear();
this.forwardHashMap.putAll(biMap.forwardHashMap);
this.reverseHashMap.putAll(biMap.reverseHashMap);
}
/**
* Replaces all of the mappings from the specified map to this bimap.
* These mappings will replace any mappings that this map had for
* any of the keys currently in the specified map. This is an alternate
* form of {@link #replaceAll(Map)} replaceAll(K, V) that will silently
* ignore duplicates
*
* @param hashMap mappings to be stored in this map
*
* @throws NullPointerException if the specified map is null
*/
public synchronized
void replaceAllForce(final Map<K, V> hashMap) {
if (hashMap == null) {
throw new NullPointerException("hashMap");
}
// only if there are no problems with the creation of the new bimap.
this.forwardHashMap.clear();
this.reverseHashMap.clear();
putAllForce(hashMap);
}
/**
* Associates the specified value with the specified key in this bimap.
* If the bimap previously contained a mapping for the key, the old
* value is replaced. If the given value is already bound to a different
* key in this bimap, the bimap will remain unmodified. To avoid throwing
* an exception, call {@link #putForce(Object, Object)} putForce(K, V) instead.
*
* @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 <tt>key</tt>, or
* <tt>null</tt> if there was no mapping for <tt>key</tt>.
* (A <tt>null</tt> return can also indicate that the map
* previously associated <tt>null</tt> with <tt>key</tt>.)
*
* @throws IllegalArgumentException if the given value is already bound to a different key in this bimap. The bimap will remain
* unmodified in this event. To avoid this exception, call {@link #putForce(Object, Object)} putForce(K, V) instead.
*/
public synchronized
V put(final K key, final V value) throws IllegalArgumentException {
V prevForwardValue = this.forwardHashMap.put(key, value);
if (prevForwardValue != null) {
reverseHashMap.remove(prevForwardValue);
}
K prevReverseValue = this.reverseHashMap.put(value, key);
if (prevReverseValue != null) {
// put the old value back
this.forwardHashMap.remove(key);
this.reverseHashMap.put(value, prevReverseValue);
throw new IllegalArgumentException("Value already exists. Keys and values must both be unique!");
}
return prevForwardValue;
}
/**
* Associates the specified value with the specified key in this bimap.
* If the bimap previously contained a mapping for the key, the old
* value is replaced. This is an alternate form of {@link #put(Object, Object)} put(K, V)
* that will silently ignore duplicates
*
* @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 <tt>key</tt>, or
* <tt>null</tt> if there was no mapping for <tt>key</tt>.
* (A <tt>null</tt> return can also indicate that the map
* previously associated <tt>null</tt> with <tt>key</tt>.)
*/
public synchronized
V putForce(final K key, final V value) {
V prevForwardValue = this.forwardHashMap.put(key, value);
if (prevForwardValue != null) {
reverseHashMap.remove(prevForwardValue);
}
K prevReverseValue = this.reverseHashMap.put(value, key);
if (prevReverseValue != null) {
forwardHashMap.remove(prevReverseValue);
}
return prevForwardValue;
}
/**
* 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 hashMap mappings to be stored in this map
*
* @throws NullPointerException if the specified map is null
*
* @throws IllegalArgumentException if the given value is already bound to a different key in this bimap. The bimap will remain
* unmodified in this event. To avoid this exception, call {@link #putAllForce(Map)} putAllForce(K, V) instead.
*/
public synchronized
void putAll(final Map<K, V> hashMap) throws IllegalArgumentException {
LockFreeBiMap<K, V> biMap = new LockFreeBiMap<K, V>();
try {
for (Map.Entry<K, V> entry : hashMap.entrySet()) {
K key = entry.getKey();
V value = entry.getValue();
biMap.put(key, value);
// we have to verify that the keys/values between the bimaps are unique
if (this.forwardHashMap.containsKey(key)) {
throw new IllegalArgumentException("Key already exists. Keys and values must both be unique!");
}
if (this.reverseHashMap.containsValue(value)) {
throw new IllegalArgumentException("Value already exists. Keys and values must both be unique!");
}
}
} catch (IllegalArgumentException e) {
// do nothing if there is an exception
throw e;
}
// only if there are no problems with the creation of the new bimap AND the uniqueness constrain is guaranteed
this.forwardHashMap.putAll(biMap.forwardHashMap);
this.reverseHashMap.putAll(biMap.reverseHashMap);
}
/**
* 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. This is an alternate
* form of {@link #putAll(Map)} putAll(K, V) that will silently
* ignore duplicates
*
* @param hashMap mappings to be stored in this map
*
* @throws NullPointerException if the specified map is null
*/
public synchronized
void putAllForce(final Map<K, V> hashMap) {
for (Map.Entry<K, V> entry : hashMap.entrySet()) {
K key = entry.getKey();
V value = entry.getValue();
putForce(key, value);
}
}
/**
* 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 <tt>key</tt>, or
* <tt>null</tt> if there was no mapping for <tt>key</tt>.
* (A <tt>null</tt> return can also indicate that the map
* previously associated <tt>null</tt> with <tt>key</tt>.)
*/
public synchronized
V remove(final K key) {
V value = forwardHashMap.remove(key);
reverseHashMap.remove(value);
return value;
}
/**
* Returns <tt>true</tt> if this map maps one or more keys to the
* specified value.
*
* @param key 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(final K key) {
// use the SWP to get a lock-free get of the value
return forwardREF.get(this).containsValue(key);
}
/**
* 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 containsReverseValue(final V value) {
// use the SWP to get a lock-free get of the value
return reverseREF.get(this).containsValue(value);
}
/**
* Returns the value to which the specified key is mapped,
* or {@code null} if this map contains no mapping for the key.
* <p>
* <p>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.)
* <p>
* <p>A return value of {@code null} does not <i>necessarily</i>
* 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 HashMap#containsKey containsKey} operation may be used to
* distinguish these two cases.
*
* @see #put(Object, Object)
*/
@SuppressWarnings("unchecked")
public
V get(final K key) {
// use the SWP to get a lock-free get of the value
return (V) forwardREF.get(this).get(key);
}
/**
* Returns the reverse key to which the specified key is mapped,
* or {@code null} if this map contains no mapping for the key.
* <p>
* <p>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.)
* <p>
* <p>A return value of {@code null} does not <i>necessarily</i>
* 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 HashMap#containsKey containsKey} operation may be used to
* distinguish these two cases.
*
* @see #put(Object, Object)
*/
@SuppressWarnings("unchecked")
public
K getReverse(final V key) {
// use the SWP to get a lock-free get of the value
return (K) reverseREF.get(this).get(key);
}
/**
* 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 <tt>remove</tt> operation),
* the results of the iteration are undefined. 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 view of the values contained in this map
*/
@SuppressWarnings("unchecked")
public
Collection<V> values() {
// use the SWP to get a lock-free get of the value
return forwardREF.get(this).values();
}
/**
* Returns <tt>true</tt> if this bimap contains no key-value mappings.
*
* @return <tt>true</tt> if this bimap contains no key-value mappings
*/
public
boolean isEmpty() {
// use the SWP to get a lock-free get of the value
return forwardREF.get(this)
.isEmpty();
}
/**
* 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 <tt>remove</tt> operation),
* the results of the iteration are undefined. 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 view of the values contained in this map
*/
@SuppressWarnings("unchecked")
public
Collection<K> reverseValues() {
// use the SWP to get a lock-free get of the value
return reverseREF.get(this).values();
}
}

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src/dorkbox/util/collections/LockFreeHashMap.java Normal file
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/*
* Copyright 2015 dorkbox, llc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package dorkbox.util.collections;
import java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
/**
* This class uses the "single-writer-principle" for lock-free publication.
* <p>
* Since there are only 2 methods to guarantee that modifications can only be called one-at-a-time (either it is only called by
* one thread, or only one thread can access it at a time) -- we chose the 2nd option -- and use 'synchronized' to make sure that only
* one thread can access this modification methods at a time. Getting or checking the presence of values can then happen in a lock-free
* manner.
* <p>
* According to my benchmarks, this is approximately 25% faster than ConcurrentHashMap for (all types of) reads, and a lot slower for
* contended writes.
* <p>
* This data structure is for many-read/few-write scenarios
*/
public final
class LockFreeHashMap<K, V> implements Map<K, V>, Cloneable, Serializable {
// Recommended for best performance while adhering to the "single writer principle". Must be static-final
private static final AtomicReferenceFieldUpdater<LockFreeHashMap, HashMap> deviceREF = AtomicReferenceFieldUpdater.newUpdater(
LockFreeHashMap.class,
HashMap.class,
"hashMap");
private volatile HashMap<K, V> hashMap;
// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
// use-case 99% of the time)
/**
* Constructs an empty <tt>HashMap</tt> with the default initial capacity
* (16) and the default load factor (0.75).
*/
public
LockFreeHashMap() {
hashMap = new HashMap<K, V>();
}
/**
* Constructs an empty <tt>HashMap</tt> with the specified initial
* capacity and the default load factor (0.75).
*
* @param initialCapacity the initial capacity.
*
* @throws IllegalArgumentException if the initial capacity is negative.
*/
public
LockFreeHashMap(int initialCapacity) {
hashMap = new HashMap<K, V>(initialCapacity);
}
/**
* Constructs a new <tt>HashMap</tt> with the same mappings as the
* specified <tt>Map</tt>. The <tt>HashMap</tt> is created with
* default load factor (0.75) and an initial capacity sufficient to
* hold the mappings in the specified <tt>Map</tt>.
*
* @param map the map whose mappings are to be placed in this map
*
* @throws NullPointerException if the specified map is null
*/
public
LockFreeHashMap(Map<K, V> map) {
this.hashMap = new HashMap<K, V>(map);
}
/**
* Constructs an empty <tt>HashMap</tt> with the specified initial
* capacity and load factor.
*
* @param initialCapacity the initial capacity
* @param loadFactor the load factor
*
* @throws IllegalArgumentException if the initial capacity is negative
* or the load factor is nonpositive
*/
public
LockFreeHashMap(int initialCapacity, float loadFactor) {
this.hashMap = new HashMap<K, V>(initialCapacity, loadFactor);
}
public synchronized
void replaceAll(final Map<K, V> hashMap) {
if (hashMap == null) {
throw new NullPointerException("hashMap");
}
this.hashMap.clear();
this.hashMap.putAll(hashMap);
}
@SuppressWarnings("unchecked")
public
Map<K, V> elements() {
// use the SWP to get a lock-free get of the map. It's values are only valid at the moment this method is called.
return Collections.unmodifiableMap(deviceREF.get(this));
}
@Override
public
int size() {
// use the SWP to get a lock-free get of the value
return deviceREF.get(this)
.size();
}
@Override
public
boolean isEmpty() {
// use the SWP to get a lock-free get of the value
return deviceREF.get(this)
.isEmpty();
}
@Override
public
boolean containsKey(final Object key) {
// use the SWP to get a lock-free get of the value
return deviceREF.get(this)
.containsKey(key);
}
@Override
public
boolean containsValue(final Object value) {
// use the SWP to get a lock-free get of the value
return deviceREF.get(this)
.containsValue(value);
}
@Override
public
V get(final Object key) {
// use the SWP to get a lock-free get of the value
return (V) deviceREF.get(this)
.get(key);
}
@Override
public synchronized
V put(final K key, final V value) {
return hashMap.put(key, value);
}
@Override
public synchronized
V remove(final Object key) {
return hashMap.remove(key);
}
@Override
public synchronized
void putAll(final Map<? extends K, ? extends V> map) {
this.hashMap.putAll(map);
}
@Override
public synchronized
void clear() {
hashMap.clear();
}
@Override
public
Set<K> keySet() {
return elements().keySet();
}
@Override
public
Collection<V> values() {
return elements().values();
}
@Override
public
Set<Entry<K, V>> entrySet() {
return elements().entrySet();
}
}

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src/dorkbox/util/collections/LockFreeSet.java Normal file
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/*
* Copyright 2015 dorkbox, llc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package dorkbox.util.collections;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
/**
* This class uses the "single-writer-principle" for lock-free publication.
* <p>
* Since there are only 2 methods to guarantee that modifications can only be called one-at-a-time (either it is only called by
* one thread, or only one thread can access it at a time) -- we chose the 2nd option -- and use 'synchronized' to make sure that only
* one thread can access this modification methods at a time. Getting or checking the presence of values can then happen in a lock-free
* manner.
* <p>
* According to my benchmarks, this is approximately 25% faster than ConcurrentHashMap for (all types of) reads, and a lot slower for
* contended writes.
* <p>
* This data structure is for many-read/few-write scenarios
*/
public final
class LockFreeSet<E> implements Set<E>, Cloneable, java.io.Serializable {
// Recommended for best performance while adhering to the "single writer principle". Must be static-final
private static final AtomicReferenceFieldUpdater<LockFreeSet, Set> setREF = AtomicReferenceFieldUpdater.newUpdater(LockFreeSet.class,
Set.class,
"hashSet");
private volatile Set<E> hashSet;
// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
// use-case 99% of the time)
/**
* Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
* default initial capacity (16) and load factor (0.75).
*/
public
LockFreeSet() {
hashSet = new HashSet<E>();
}
/**
* Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
* the specified initial capacity and the specified load factor.
*
* @param initialCapacity the initial capacity of the hash map
* @param loadFactor the load factor of the hash map
*
* @throws IllegalArgumentException if the initial capacity is less
* than zero, or if the load factor is nonpositive
*/
public
LockFreeSet(int initialCapacity, float loadFactor) {
hashSet = new HashSet<E>(initialCapacity, loadFactor);
}
/**
* Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
* the specified initial capacity and default load factor (0.75).
*
* @param initialCapacity the initial capacity of the hash table
*
* @throws IllegalArgumentException if the initial capacity is less
* than zero
*/
public
LockFreeSet(int initialCapacity) {
hashSet = new HashSet<E>(initialCapacity);
}
/**
* Constructs a new set containing the elements in the specified
* collection. The <tt>HashMap</tt> is created with default load factor
* (0.75) and an initial capacity sufficient to contain the elements in
* the specified collection.
*
* @param collection the collection whose elements are to be placed into this set
*
* @throws NullPointerException if the specified collection is null
*/
public
LockFreeSet(final Collection<E> collection) {
hashSet = new HashSet<E>(collection);
}
@SuppressWarnings("unchecked")
public
Set<E> elements() {
// use the SWP to get a lock-free get of the value
return Collections.unmodifiableSet(setREF.get(this));
}
@Override
public
int size() {
return setREF.get(this)
.size();
}
@Override
public
boolean isEmpty() {
// use the SWP to get a lock-free get of the value
return setREF.get(this)
.isEmpty();
}
@Override
public
boolean contains(final Object element) {
// use the SWP to get a lock-free get of the value
return setREF.get(this)
.contains(element);
}
@Override
public
Iterator<E> iterator() {
return elements().iterator();
}
@Override
public
Object[] toArray() {
return setREF.get(this)
.toArray();
}
@Override
public
<T> T[] toArray(final T[] a) {
return (T[]) setREF.get(this)
.toArray(a);
}
@Override
public synchronized
boolean add(final E element) {
return hashSet.add(element);
}
@Override
public synchronized
boolean remove(final Object element) {
return hashSet.remove(element);
}
@Override
public
boolean containsAll(final Collection<?> collection) {
// use the SWP to get a lock-free get of the value
return setREF.get(this)
.containsAll(collection);
}
@Override
public synchronized
boolean addAll(final Collection<? extends E> elements) {
return hashSet.addAll(elements);
}
@Override
public synchronized
boolean retainAll(final Collection<?> collection) {
return hashSet.retainAll(collection);
}
@Override
public synchronized
boolean removeAll(final Collection<?> collection) {
return hashSet.removeAll(collection);
}
@Override
public synchronized
void clear() {
hashSet.clear();
}
}