Added 2 missing lockfree types
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109
src/dorkbox/util/collections/LockFreeArrayList.java
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109
src/dorkbox/util/collections/LockFreeArrayList.java
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/*
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* Copyright 2018 dorkbox, llc
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package dorkbox.util.collections;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
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/**
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* This class uses the "single-writer-principle" for lock-free publication.
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*
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* Since there are only 2 methods to guarantee that modifications can only be called one-at-a-time (either it is only called by
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* 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
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* one thread can access this modification methods at a time. Getting or checking the presence of values can then happen in a lock-free
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* manner.
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*
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* According to my benchmarks, this is approximately 25% faster than ConcurrentHashMap for (all types of) reads, and a lot slower for
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* contended writes.
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*
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* This data structure is for many-read/few-write scenarios
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*/
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public final
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class LockFreeArrayList<E> {
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// Recommended for best performance while adhering to the "single writer principle". Must be static-final
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private static final AtomicReferenceFieldUpdater<LockFreeArrayList, ArrayList> listRef =
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AtomicReferenceFieldUpdater.newUpdater(LockFreeArrayList.class,
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ArrayList.class, "arrayList");
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private volatile ArrayList<E> arrayList = new ArrayList<>();
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public
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LockFreeArrayList(){}
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public
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LockFreeArrayList(Collection<E> elements) {
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arrayList.addAll(elements);
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}
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// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
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// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
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// use-case 99% of the time)
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public synchronized
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void clear() {
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arrayList.clear();
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}
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// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
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// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
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// use-case 99% of the time)
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public synchronized
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boolean add(final E element) {
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return arrayList.add(element);
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}
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// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
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// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
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// use-case 99% of the time)
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public synchronized
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void addAll(final Collection<E> elements) {
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arrayList.addAll(elements);
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}
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public synchronized
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E get(int index) {
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return arrayList.get(index);
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}
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// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
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// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
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// use-case 99% of the time)
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public synchronized
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boolean remove(final E element) {
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return arrayList.remove(element);
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}
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public
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int size() {
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return listRef.get(this).size();
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}
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// lock-free get
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public
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boolean contains(final E element) {
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// use the SWP to get the value
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return listRef.get(this).contains(element);
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}
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// lock-free get
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@SuppressWarnings("unchecked")
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public
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ArrayList<E> elements() {
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// use the SWP to get the value
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return listRef.get(this);
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}
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}
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106
src/dorkbox/util/collections/LockFreeHashSet.java
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106
src/dorkbox/util/collections/LockFreeHashSet.java
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@ -0,0 +1,106 @@
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/*
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* Copyright 2018 dorkbox, llc
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package dorkbox.util.collections;
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import java.util.Collection;
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import java.util.HashSet;
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import java.util.Set;
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import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
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/**
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* This class uses the "single-writer-principle" for lock-free publication.
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*
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* Since there are only 2 methods to guarantee that modifications can only be called one-at-a-time (either it is only called by
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* 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
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* one thread can access this modification methods at a time. Getting or checking the presence of values can then happen in a lock-free
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* manner.
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*
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* According to my benchmarks, this is approximately 25% faster than ConcurrentHashMap for (all types of) reads, and a lot slower for
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* contended writes.
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*
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* This data structure is for many-read/few-write scenarios
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*/
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public final
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class LockFreeHashSet<E> {
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// Recommended for best performance while adhering to the "single writer principle". Must be static-final
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private static final AtomicReferenceFieldUpdater<LockFreeHashSet, Set> setREF =
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AtomicReferenceFieldUpdater.newUpdater(LockFreeHashSet.class,
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Set.class,
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"hashSet");
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private volatile Set<E> hashSet = new HashSet<>();
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public
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LockFreeHashSet(){}
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public
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LockFreeHashSet(Collection<E> elements) {
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hashSet.addAll(elements);
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}
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// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
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// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
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// use-case 99% of the time)
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public synchronized
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void clear() {
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hashSet.clear();
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}
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// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
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// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
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// use-case 99% of the time)
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public synchronized
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boolean add(final E element) {
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return hashSet.add(element);
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}
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// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
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// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
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// use-case 99% of the time)
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public synchronized
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void addAll(final Collection<E> elements) {
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hashSet.addAll(elements);
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}
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// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
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// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
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// use-case 99% of the time)
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public synchronized
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boolean remove(final E element) {
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return hashSet.remove(element);
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}
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// lock-free get
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public
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boolean contains(final E element) {
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// use the SWP to get the value
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return setREF.get(this).contains(element);
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}
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// lock-free get
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@SuppressWarnings("unchecked")
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public
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Set<E> elements() {
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// use the SWP to get the value
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return setREF.get(this);
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}
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public
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int size() {
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return setREF.get(this).size();
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}
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}
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