/*
	* Copyright (C) 2002-2019 Sebastiano Vigna
	*
	* 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 it.unimi.dsi.fastutil.objects;
import it.unimi.dsi.fastutil.Hash;
import it.unimi.dsi.fastutil.HashCommon;
import static it.unimi.dsi.fastutil.HashCommon.arraySize;
import static it.unimi.dsi.fastutil.HashCommon.maxFill;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
A type-specific hash set with a fast, small-footprint implementation whose hashing strategy is specified at creation time. 

Instances of this class use a hash table to represent a set. The table is
filled up to a specified load factor, and then doubled in size to
accommodate new entries. If the table is emptied below one fourth of
the load factor, it is halved in size; however, the table is never reduced to
a size smaller than that at creation time: this approach makes it possible to
create sets with a large capacity in which insertions and deletions do not
cause immediately rehashing. Moreover, halving is not performed when deleting
entries from an iterator, as it would interfere with the iteration process.
 Note that clear() does not modify the hash table size. Rather, a family of trimming methods lets you control the size of the table; this is particularly useful if you reuse instances of this class. 
See Also:
Hash
HashCommon/**
 * A type-specific hash set with a fast, small-footprint implementation whose
 * {@linkplain it.unimi.dsi.fastutil.Hash.Strategy hashing strategy} is
 * specified at creation time.
 *
 * <p>
 * Instances of this class use a hash table to represent a set. The table is
 * filled up to a specified <em>load factor</em>, and then doubled in size to
 * accommodate new entries. If the table is emptied below <em>one fourth</em> of
 * the load factor, it is halved in size; however, the table is never reduced to
 * a size smaller than that at creation time: this approach makes it possible to
 * create sets with a large capacity in which insertions and deletions do not
 * cause immediately rehashing. Moreover, halving is not performed when deleting
 * entries from an iterator, as it would interfere with the iteration process.
 *
 * <p>
 * Note that {@link #clear()} does not modify the hash table size. Rather, a
 * family of {@linkplain #trim() trimming methods} lets you control the size of
 * the table; this is particularly useful if you reuse instances of this class.
 *
 * @see Hash
 * @see HashCommon
 */
public class ObjectOpenCustomHashSet<K> extends AbstractObjectSet<K> implements java.io.Serializable, Cloneable, Hash {
	private static final long serialVersionUID = 0L;
	private static final boolean ASSERTS = false;
	
The array of keys. /** The array of keys. */
	protected transient K[] key;
	
The mask for wrapping a position counter. /** The mask for wrapping a position counter. */
	protected transient int mask;
	
Whether this set contains the null key. /** Whether this set contains the null key. */
	protected transient boolean containsNull;
	
The hash strategy of this custom set. /** The hash strategy of this custom set. */
	protected Strategy<? super K> strategy;
	
The current table size. Note that an additional element is allocated for
storing the null key.
/**
	 * The current table size. Note that an additional element is allocated for
	 * storing the null key.
	 */
	protected transient int n;
	
Threshold after which we rehash. It must be the table size times ObjectOpenCustomHashSet<K>.f. /**
	 * Threshold after which we rehash. It must be the table size times {@link #f}.
	 */
	protected transient int maxFill;
	
We never resize below this threshold, which is the construction-time {#n}.
/**
	 * We never resize below this threshold, which is the construction-time {#n}.
	 */
	protected final transient int minN;
	
Number of entries in the set (including the null key, if present). /** Number of entries in the set (including the null key, if present). */
	protected int size;
	
The acceptable load factor. /** The acceptable load factor. */
	protected final float f;
	
Creates a new hash set.
 The actual table size will be the least power of two greater than expected/f. 
Params:
expected – 
           the expected number of elements in the hash set.
f – 
           the load factor.
strategy – 
           the strategy./**
	 * Creates a new hash set.
	 *
	 * <p>
	 * The actual table size will be the least power of two greater than
	 * {@code expected}/{@code f}.
	 *
	 * @param expected
	 *            the expected number of elements in the hash set.
	 * @param f
	 *            the load factor.
	 * @param strategy
	 *            the strategy.
	 */
	@SuppressWarnings("unchecked")
	public ObjectOpenCustomHashSet(final int expected, final float f, final Strategy<? super K> strategy) {
		this.strategy = strategy;
		if (f <= 0 || f > 1)
			throw new IllegalArgumentException("Load factor must be greater than 0 and smaller than or equal to 1");
		if (expected < 0)
			throw new IllegalArgumentException("The expected number of elements must be nonnegative");
		this.f = f;
		minN = n = arraySize(expected, f);
		mask = n - 1;
		maxFill = maxFill(n, f);
		key = (K[]) new Object[n + 1];
	}
	
Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor. 
Params:
expected – 
           the expected number of elements in the hash set.
strategy – 
           the strategy./**
	 * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
	 *
	 * @param expected
	 *            the expected number of elements in the hash set.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final int expected, final Strategy<? super K> strategy) {
		this(expected, DEFAULT_LOAD_FACTOR, strategy);
	}
	
Creates a new hash set with initial expected Hash.DEFAULT_INITIAL_SIZE elements and Hash.DEFAULT_LOAD_FACTOR as load factor. 
Params:
strategy – 
           the strategy./**
	 * Creates a new hash set with initial expected
	 * {@link Hash#DEFAULT_INITIAL_SIZE} elements and
	 * {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
	 * 
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final Strategy<? super K> strategy) {
		this(DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR, strategy);
	}
	
Creates a new hash set copying a given collection.
Params:
c –  a Collection to be copied into the new hash set.
f – 
           the load factor.
strategy – 
           the strategy./**
	 * Creates a new hash set copying a given collection.
	 *
	 * @param c
	 *            a {@link Collection} to be copied into the new hash set.
	 * @param f
	 *            the load factor.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final Collection<? extends K> c, final float f, final Strategy<? super K> strategy) {
		this(c.size(), f, strategy);
		addAll(c);
	}
	
Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given collection. 
Params:
c –  a Collection to be copied into the new hash set.
strategy – 
           the strategy./**
	 * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
	 * copying a given collection.
	 *
	 * @param c
	 *            a {@link Collection} to be copied into the new hash set.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final Collection<? extends K> c, final Strategy<? super K> strategy) {
		this(c, DEFAULT_LOAD_FACTOR, strategy);
	}
	
Creates a new hash set copying a given type-specific collection.
Params:
c – 
           a type-specific collection to be copied into the new hash set.
f – 
           the load factor.
strategy – 
           the strategy./**
	 * Creates a new hash set copying a given type-specific collection.
	 *
	 * @param c
	 *            a type-specific collection to be copied into the new hash set.
	 * @param f
	 *            the load factor.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final ObjectCollection<? extends K> c, final float f, Strategy<? super K> strategy) {
		this(c.size(), f, strategy);
		addAll(c);
	}
	
Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific collection. 
Params:
c – 
           a type-specific collection to be copied into the new hash set.
strategy – 
           the strategy./**
	 * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
	 * copying a given type-specific collection.
	 *
	 * @param c
	 *            a type-specific collection to be copied into the new hash set.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final ObjectCollection<? extends K> c, final Strategy<? super K> strategy) {
		this(c, DEFAULT_LOAD_FACTOR, strategy);
	}
	
Creates a new hash set using elements provided by a type-specific iterator.
Params:
i – 
           a type-specific iterator whose elements will fill the set.
f – 
           the load factor.
strategy – 
           the strategy./**
	 * Creates a new hash set using elements provided by a type-specific iterator.
	 *
	 * @param i
	 *            a type-specific iterator whose elements will fill the set.
	 * @param f
	 *            the load factor.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final Iterator<? extends K> i, final float f, final Strategy<? super K> strategy) {
		this(DEFAULT_INITIAL_SIZE, f, strategy);
		while (i.hasNext())
			add(i.next());
	}
	
Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor using elements provided by a type-specific iterator. 
Params:
i – 
           a type-specific iterator whose elements will fill the set.
strategy – 
           the strategy./**
	 * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
	 * using elements provided by a type-specific iterator.
	 *
	 * @param i
	 *            a type-specific iterator whose elements will fill the set.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final Iterator<? extends K> i, final Strategy<? super K> strategy) {
		this(i, DEFAULT_LOAD_FACTOR, strategy);
	}
	
Creates a new hash set and fills it with the elements of a given array.
Params:
a – 
           an array whose elements will be used to fill the set.
offset – 
           the first element to use.
length – 
           the number of elements to use.
f – 
           the load factor.
strategy – 
           the strategy./**
	 * Creates a new hash set and fills it with the elements of a given array.
	 *
	 * @param a
	 *            an array whose elements will be used to fill the set.
	 * @param offset
	 *            the first element to use.
	 * @param length
	 *            the number of elements to use.
	 * @param f
	 *            the load factor.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final K[] a, final int offset, final int length, final float f,
			final Strategy<? super K> strategy) {
		this(length < 0 ? 0 : length, f, strategy);
		ObjectArrays.ensureOffsetLength(a, offset, length);
		for (int i = 0; i < length; i++)
			add(a[offset + i]);
	}
	
Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor and fills it with the elements of a given array. 
Params:
a – 
           an array whose elements will be used to fill the set.
offset – 
           the first element to use.
length – 
           the number of elements to use.
strategy – 
           the strategy./**
	 * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
	 * and fills it with the elements of a given array.
	 *
	 * @param a
	 *            an array whose elements will be used to fill the set.
	 * @param offset
	 *            the first element to use.
	 * @param length
	 *            the number of elements to use.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final K[] a, final int offset, final int length,
			final Strategy<? super K> strategy) {
		this(a, offset, length, DEFAULT_LOAD_FACTOR, strategy);
	}
	
Creates a new hash set copying the elements of an array.
Params:
a – 
           an array to be copied into the new hash set.
f – 
           the load factor.
strategy – 
           the strategy./**
	 * Creates a new hash set copying the elements of an array.
	 *
	 * @param a
	 *            an array to be copied into the new hash set.
	 * @param f
	 *            the load factor.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final K[] a, final float f, final Strategy<? super K> strategy) {
		this(a, 0, a.length, f, strategy);
	}
	
Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying the elements of an array. 
Params:
a – 
           an array to be copied into the new hash set.
strategy – 
           the strategy./**
	 * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
	 * copying the elements of an array.
	 *
	 * @param a
	 *            an array to be copied into the new hash set.
	 * @param strategy
	 *            the strategy.
	 */
	public ObjectOpenCustomHashSet(final K[] a, final Strategy<? super K> strategy) {
		this(a, DEFAULT_LOAD_FACTOR, strategy);
	}
	
Returns the hashing strategy.
Returns:
the hashing strategy of this custom hash set./**
	 * Returns the hashing strategy.
	 *
	 * @return the hashing strategy of this custom hash set.
	 */
	public Strategy<? super K> strategy() {
		return strategy;
	}
	private int realSize() {
		return containsNull ? size - 1 : size;
	}
	private void ensureCapacity(final int capacity) {
		final int needed = arraySize(capacity, f);
		if (needed > n)
			rehash(needed);
	}
	private void tryCapacity(final long capacity) {
		final int needed = (int) Math.min(1 << 30,
				Math.max(2, HashCommon.nextPowerOfTwo((long) Math.ceil(capacity / f))));
		if (needed > n)
			rehash(needed);
	}
	@Override
	public boolean addAll(Collection<? extends K> c) {
		// The resulting collection will be at least c.size() big
		if (f <= .5)
			ensureCapacity(c.size()); // The resulting collection will be sized for c.size() elements
		else
			tryCapacity(size() + c.size()); // The resulting collection will be tentatively sized for size() + c.size()
											// elements
		return super.addAll(c);
	}
	@Override
	public boolean add(final K k) {
		int pos;
		if ((strategy.equals((k), (null)))) {
			if (containsNull)
				return false;
			containsNull = true;
			key[n] = k;
		} else {
			K curr;
			final K[] key = this.key;
			// The starting point.
			if (!((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(k))) & mask]) == null)) {
				if ((strategy.equals((curr), (k))))
					return false;
				while (!((curr = key[pos = (pos + 1) & mask]) == null))
					if ((strategy.equals((curr), (k))))
						return false;
			}
			key[pos] = k;
		}
		if (size++ >= maxFill)
			rehash(arraySize(size + 1, f));
		if (ASSERTS)
			checkTable();
		return true;
	}
	
Add a random element if not present, get the existing value if already
present.
This is equivalent to (but faster than) doing a:
K exist = set.get(k);
if (exist == null) {
	set.add(k);
	exist = k;
}

/**
	 * Add a random element if not present, get the existing value if already
	 * present.
	 *
	 * This is equivalent to (but faster than) doing a:
	 * 
	 * <pre>
	 * K exist = set.get(k);
	 * if (exist == null) {
	 * 	set.add(k);
	 * 	exist = k;
	 * }
	 * </pre>
	 */
	public K addOrGet(final K k) {
		int pos;
		if ((strategy.equals((k), (null)))) {
			if (containsNull)
				return key[n];
			containsNull = true;
			key[n] = k;
		} else {
			K curr;
			final K[] key = this.key;
			// The starting point.
			if (!((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(k))) & mask]) == null)) {
				if ((strategy.equals((curr), (k))))
					return curr;
				while (!((curr = key[pos = (pos + 1) & mask]) == null))
					if ((strategy.equals((curr), (k))))
						return curr;
			}
			key[pos] = k;
		}
		if (size++ >= maxFill)
			rehash(arraySize(size + 1, f));
		if (ASSERTS)
			checkTable();
		return k;
	}
	
Shifts left entries with the specified hash code, starting at the specified
position, and empties the resulting free entry.
Params:
pos – 
           a starting position./**
	 * Shifts left entries with the specified hash code, starting at the specified
	 * position, and empties the resulting free entry.
	 *
	 * @param pos
	 *            a starting position.
	 */
	protected final void shiftKeys(int pos) {
		// Shift entries with the same hash.
		int last, slot;
		K curr;
		final K[] key = this.key;
		for (;;) {
			pos = ((last = pos) + 1) & mask;
			for (;;) {
				if (((curr = key[pos]) == null)) {
					key[last] = (null);
					return;
				}
				slot = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(curr))) & mask;
				if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos)
					break;
				pos = (pos + 1) & mask;
			}
			key[last] = curr;
		}
	}
	private boolean removeEntry(final int pos) {
		size--;
		shiftKeys(pos);
		if (n > minN && size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
			rehash(n / 2);
		return true;
	}
	private boolean removeNullEntry() {
		containsNull = false;
		key[n] = (null);
		size--;
		if (n > minN && size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
			rehash(n / 2);
		return true;
	}
	@SuppressWarnings("unchecked")
	@Override
	public boolean remove(final Object k) {
		if ((strategy.equals(((K) k), (null)))) {
			if (containsNull)
				return removeNullEntry();
			return false;
		}
		K curr;
		final K[] key = this.key;
		int pos;
		// The starting point.
		if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode((K) k))) & mask]) == null))
			return false;
		if ((strategy.equals((K) (k), (curr))))
			return removeEntry(pos);
		while (true) {
			if (((curr = key[pos = (pos + 1) & mask]) == null))
				return false;
			if ((strategy.equals((K) (k), (curr))))
				return removeEntry(pos);
		}
	}
	@SuppressWarnings("unchecked")
	@Override
	public boolean contains(final Object k) {
		if ((strategy.equals(((K) k), (null))))
			return containsNull;
		K curr;
		final K[] key = this.key;
		int pos;
		// The starting point.
		if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode((K) k))) & mask]) == null))
			return false;
		if ((strategy.equals((K) (k), (curr))))
			return true;
		while (true) {
			if (((curr = key[pos = (pos + 1) & mask]) == null))
				return false;
			if ((strategy.equals((K) (k), (curr))))
				return true;
		}
	}
	
Returns the element of this set that is equal to the given key, or null. 
Returns:
the element of this set that is equal to the given key, or null./**
	 * Returns the element of this set that is equal to the given key, or
	 * {@code null}.
	 * 
	 * @return the element of this set that is equal to the given key, or
	 *         {@code null}.
	 */
	@SuppressWarnings("unchecked")
	public K get(final Object k) {
		if ((strategy.equals(((K) k), (null))))
			return key[n]; // This is correct independently of the value of containsNull and of the set
							// being custom
		K curr;
		final K[] key = this.key;
		int pos;
		// The starting point.
		if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode((K) k))) & mask]) == null))
			return null;
		if ((strategy.equals((K) (k), (curr))))
			return curr;
		// There's always an unused entry.
		while (true) {
			if (((curr = key[pos = (pos + 1) & mask]) == null))
				return null;
			if ((strategy.equals((K) (k), (curr))))
				return curr;
		}
	}
	/*
	 * Removes all elements from this set.
	 *
	 * <p>To increase object reuse, this method does not change the table size. If
	 * you want to reduce the table size, you must use {@link #trim()}.
	 *
	 */
	@Override
	public void clear() {
		if (size == 0)
			return;
		size = 0;
		containsNull = false;
		Arrays.fill(key, (null));
	}
	@Override
	public int size() {
		return size;
	}
	@Override
	public boolean isEmpty() {
		return size == 0;
	}
	
An iterator over a hash set. /** An iterator over a hash set. */
	private class SetIterator implements ObjectIterator<K> {
		
The index of the last entry returned, if positive or zero; initially, ObjectOpenCustomHashSet<K>.n. If negative, the last element returned was that of index - pos - 1 from the SetIterator.wrapped list. /**
		 * The index of the last entry returned, if positive or zero; initially,
		 * {@link #n}. If negative, the last element returned was that of index
		 * {@code - pos - 1} from the {@link #wrapped} list.
		 */
		int pos = n;
		
The index of the last entry that has been returned (more precisely, the value of SetIterator.pos if SetIterator.pos is positive, or Integer.MIN_VALUE if SetIterator.pos is negative). It is -1 if either we did not return an entry yet, or the last returned entry has been removed. /**
		 * The index of the last entry that has been returned (more precisely, the value
		 * of {@link #pos} if {@link #pos} is positive, or {@link Integer#MIN_VALUE} if
		 * {@link #pos} is negative). It is -1 if either we did not return an entry yet,
		 * or the last returned entry has been removed.
		 */
		int last = -1;
		
A downward counter measuring how many entries must still be returned. /** A downward counter measuring how many entries must still be returned. */
		int c = size;
		
A boolean telling us whether we should return the null key. /** A boolean telling us whether we should return the null key. */
		boolean mustReturnNull = ObjectOpenCustomHashSet.this.containsNull;
		
A lazily allocated list containing elements that have wrapped around the
table because of removals.
/**
		 * A lazily allocated list containing elements that have wrapped around the
		 * table because of removals.
		 */
		ObjectArrayList<K> wrapped;
		@Override
		public boolean hasNext() {
			return c != 0;
		}
		@Override
		public K next() {
			if (!hasNext())
				throw new NoSuchElementException();
			c--;
			if (mustReturnNull) {
				mustReturnNull = false;
				last = n;
				return key[n];
			}
			final K key[] = ObjectOpenCustomHashSet.this.key;
			for (;;) {
				if (--pos < 0) {
					// We are just enumerating elements from the wrapped list.
					last = Integer.MIN_VALUE;
					return wrapped.get(-pos - 1);
				}
				if (!((key[pos]) == null))
					return key[last = pos];
			}
		}
		
Shifts left entries with the specified hash code, starting at the specified
position, and empties the resulting free entry.
Params:
pos – 
           a starting position./**
		 * Shifts left entries with the specified hash code, starting at the specified
		 * position, and empties the resulting free entry.
		 *
		 * @param pos
		 *            a starting position.
		 */
		private final void shiftKeys(int pos) {
			// Shift entries with the same hash.
			int last, slot;
			K curr;
			final K[] key = ObjectOpenCustomHashSet.this.key;
			for (;;) {
				pos = ((last = pos) + 1) & mask;
				for (;;) {
					if (((curr = key[pos]) == null)) {
						key[last] = (null);
						return;
					}
					slot = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(curr))) & mask;
					if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos)
						break;
					pos = (pos + 1) & mask;
				}
				if (pos < last) { // Wrapped entry.
					if (wrapped == null)
						wrapped = new ObjectArrayList<>(2);
					wrapped.add(key[pos]);
				}
				key[last] = curr;
			}
		}
		@Override
		public void remove() {
			if (last == -1)
				throw new IllegalStateException();
			if (last == n) {
				ObjectOpenCustomHashSet.this.containsNull = false;
				ObjectOpenCustomHashSet.this.key[n] = (null);
			} else if (pos >= 0)
				shiftKeys(last);
			else {
				// We're removing wrapped entries.
				ObjectOpenCustomHashSet.this.remove(wrapped.set(-pos - 1, null));
				last = -1; // Note that we must not decrement size
				return;
			}
			size--;
			last = -1; // You can no longer remove this entry.
			if (ASSERTS)
				checkTable();
		}
	}
	@Override
	public ObjectIterator<K> iterator() {
		return new SetIterator();
	}
	
Rehashes this set, making the table as small as possible.

This method rehashes the table to the smallest size satisfying the load
factor. It can be used when the set will not be changed anymore, so to
optimize access speed and size.

If the table size is already the minimum possible, this method does nothing.
See Also:
trim(int)
Returns:
true if there was enough memory to trim the set./**
	 * Rehashes this set, making the table as small as possible.
	 *
	 * <p>
	 * This method rehashes the table to the smallest size satisfying the load
	 * factor. It can be used when the set will not be changed anymore, so to
	 * optimize access speed and size.
	 *
	 * <p>
	 * If the table size is already the minimum possible, this method does nothing.
	 *
	 * @return true if there was enough memory to trim the set.
	 * @see #trim(int)
	 */
	public boolean trim() {
		return trim(size);
	}
	
Rehashes this set if the table is too large.

Let N be the smallest table size that can hold
max(n,size()) entries, still satisfying the load
factor. If the current table size is smaller than or equal to N,
this method does nothing. Otherwise, it rehashes this set in a table of size
N.
 This method is useful when reusing sets. Clearing a set leaves the table size untouched. If you are reusing a set many times, you can call this method with a typical size to avoid keeping around a very large table just because of a few large transient sets. 
Params:
n – 
           the threshold for the trimming.
See Also:
trim()
Returns:
true if there was enough memory to trim the set./**
	 * Rehashes this set if the table is too large.
	 *
	 * <p>
	 * Let <var>N</var> be the smallest table size that can hold
	 * <code>max(n,{@link #size()})</code> entries, still satisfying the load
	 * factor. If the current table size is smaller than or equal to <var>N</var>,
	 * this method does nothing. Otherwise, it rehashes this set in a table of size
	 * <var>N</var>.
	 *
	 * <p>
	 * This method is useful when reusing sets. {@linkplain #clear() Clearing a set}
	 * leaves the table size untouched. If you are reusing a set many times, you can
	 * call this method with a typical size to avoid keeping around a very large
	 * table just because of a few large transient sets.
	 *
	 * @param n
	 *            the threshold for the trimming.
	 * @return true if there was enough memory to trim the set.
	 * @see #trim()
	 */
	public boolean trim(final int n) {
		final int l = HashCommon.nextPowerOfTwo((int) Math.ceil(n / f));
		if (l >= this.n || size > maxFill(l, f))
			return true;
		try {
			rehash(l);
		} catch (OutOfMemoryError cantDoIt) {
			return false;
		}
		return true;
	}
	
Rehashes the set.

This method implements the basic rehashing strategy, and may be overriden by
subclasses implementing different rehashing strategies (e.g., disk-based
rehashing). However, you should not override this method unless you
understand the internal workings of this class.
Params:
newN – 
           the new size/**
	 * Rehashes the set.
	 *
	 * <p>
	 * This method implements the basic rehashing strategy, and may be overriden by
	 * subclasses implementing different rehashing strategies (e.g., disk-based
	 * rehashing). However, you should not override this method unless you
	 * understand the internal workings of this class.
	 *
	 * @param newN
	 *            the new size
	 */
	@SuppressWarnings("unchecked")
	protected void rehash(final int newN) {
		final K key[] = this.key;
		final int mask = newN - 1; // Note that this is used by the hashing macro
		final K newKey[] = (K[]) new Object[newN + 1];
		int i = n, pos;
		for (int j = realSize(); j-- != 0;) {
			while (((key[--i]) == null));
			if (!((newKey[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(key[i]))) & mask]) == null))
				while (!((newKey[pos = (pos + 1) & mask]) == null));
			newKey[pos] = key[i];
		}
		n = newN;
		this.mask = mask;
		maxFill = maxFill(n, f);
		this.key = newKey;
	}
	
Returns a deep copy of this set.

This method performs a deep copy of this hash set; the data stored in the
set, however, is not cloned. Note that this makes a difference only for
object keys.
Returns:
a deep copy of this set./**
	 * Returns a deep copy of this set.
	 *
	 * <p>
	 * This method performs a deep copy of this hash set; the data stored in the
	 * set, however, is not cloned. Note that this makes a difference only for
	 * object keys.
	 *
	 * @return a deep copy of this set.
	 */
	@Override
	@SuppressWarnings("unchecked")
	public ObjectOpenCustomHashSet<K> clone() {
		ObjectOpenCustomHashSet<K> c;
		try {
			c = (ObjectOpenCustomHashSet<K>) super.clone();
		} catch (CloneNotSupportedException cantHappen) {
			throw new InternalError();
		}
		c.key = key.clone();
		c.containsNull = containsNull;
		c.strategy = strategy;
		return c;
	}
	
Returns a hash code for this set. This method overrides the generic method provided by the superclass. Since equals() is not overriden, it is important that the value returned by this method is the same value as the one returned by the overriden method. 
Returns:
a hash code for this set./**
	 * Returns a hash code for this set.
	 *
	 * This method overrides the generic method provided by the superclass. Since
	 * {@code equals()} is not overriden, it is important that the value returned by
	 * this method is the same value as the one returned by the overriden method.
	 *
	 * @return a hash code for this set.
	 */
	@Override
	public int hashCode() {
		int h = 0;
		for (int j = realSize(), i = 0; j-- != 0;) {
			while (((key[i]) == null))
				i++;
			if (this != key[i])
				h += (strategy.hashCode(key[i]));
			i++;
		}
		// Zero / null have hash zero.
		return h;
	}
	private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
		final ObjectIterator<K> i = iterator();
		s.defaultWriteObject();
		for (int j = size; j-- != 0;)
			s.writeObject(i.next());
	}
	@SuppressWarnings("unchecked")
	private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
		s.defaultReadObject();
		n = arraySize(size, f);
		maxFill = maxFill(n, f);
		mask = n - 1;
		final K key[] = this.key = (K[]) new Object[n + 1];
		K k;
		for (int i = size, pos; i-- != 0;) {
			k = (K) s.readObject();
			if ((strategy.equals((k), (null)))) {
				pos = n;
				containsNull = true;
			} else {
				if (!((key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(k))) & mask]) == null))
					while (!((key[pos = (pos + 1) & mask]) == null));
			}
			key[pos] = k;
		}
		if (ASSERTS)
			checkTable();
	}
	private void checkTable() {
	}
}