http://fastutil.di.unimi.it/: fastutil extends the Java Collections Framework by providing type-specific maps, sets, lists and priority queues with a small memory footprint and fast access and insertion; provides also big (64-bit) arrays, sets and lists, and fast, practical I/O classes for binary and text files.
  • Sebastiano Vigna 
/*
	* 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.shorts;
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.Map;
import java.util.Arrays;
import java.util.NoSuchElementException;
import java.util.function.Consumer;
import it.unimi.dsi.fastutil.objects.ReferenceCollection;
import it.unimi.dsi.fastutil.objects.AbstractReferenceCollection;
import it.unimi.dsi.fastutil.objects.AbstractObjectSet;
import it.unimi.dsi.fastutil.objects.ObjectIterator;

A type-specific hash map with a fast, small-footprint implementation.


Instances of this class use a hash table to represent a map. 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 maps 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:
/**
 * A type-specific hash map with a fast, small-footprint implementation.
 *
 * <p>
 * Instances of this class use a hash table to represent a map. 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 maps 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 Short2ReferenceOpenHashMap<V> extends AbstractShort2ReferenceMap<V>
		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 short[] key;
	
The array of values. 
/** The array of values. */
	protected transient V[] value;
	
The mask for wrapping a position counter. 
/** The mask for wrapping a position counter. */
	protected transient int mask;
	
Whether this map contains the key zero. 
/** Whether this map contains the key zero. */
	protected transient boolean containsNullKey;
	
The current table size. 
/** The current table size. */
	protected transient int n;
	
Threshold after which we rehash. It must be the table size times Short2ReferenceOpenHashMap<V>.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 key zero, if present). 
/** Number of entries in the set (including the key zero, if present). */
	protected int size;
	
The acceptable load factor. 
/** The acceptable load factor. */
	protected final float f;
	
Cached set of entries. 
/** Cached set of entries. */
	protected transient FastEntrySet<V> entries;
	
Cached set of keys. 
/** Cached set of keys. */
	protected transient ShortSet keys;
	
Cached collection of values. 
/** Cached collection of values. */
	protected transient ReferenceCollection<V> values;
	
Creates a new hash map.

 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 map.
  • f – 
           the load factor.
/**
	 * Creates a new hash map.
	 *
	 * <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 map.
	 * @param f
	 *            the load factor.
	 */
	@SuppressWarnings("unchecked")
	public Short2ReferenceOpenHashMap(final int expected, final float f) {
		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 = new short[n + 1];
		value = (V[]) new Object[n + 1];
	}
	
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor. 
Params:
  • expected – 
           the expected number of elements in the hash map.
/**
	 * Creates a new hash map with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
	 *
	 * @param expected
	 *            the expected number of elements in the hash map.
	 */
	public Short2ReferenceOpenHashMap(final int expected) {
		this(expected, DEFAULT_LOAD_FACTOR);
	}
	
Creates a new hash map with initial expected Hash.DEFAULT_INITIAL_SIZE entries and Hash.DEFAULT_LOAD_FACTOR as load factor. 
/**
	 * Creates a new hash map with initial expected
	 * {@link Hash#DEFAULT_INITIAL_SIZE} entries and
	 * {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
	 */
	public Short2ReferenceOpenHashMap() {
		this(DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR);
	}
	
Creates a new hash map copying a given one.

Params:
  • m –  a Map to be copied into the new hash map.
  • f – 
           the load factor.
/**
	 * Creates a new hash map copying a given one.
	 *
	 * @param m
	 *            a {@link Map} to be copied into the new hash map.
	 * @param f
	 *            the load factor.
	 */
	public Short2ReferenceOpenHashMap(final Map<? extends Short, ? extends V> m, final float f) {
		this(m.size(), f);
		putAll(m);
	}
	
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given one. 
Params:
  • m –  a Map to be copied into the new hash map.
/**
	 * Creates a new hash map with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
	 * copying a given one.
	 *
	 * @param m
	 *            a {@link Map} to be copied into the new hash map.
	 */
	public Short2ReferenceOpenHashMap(final Map<? extends Short, ? extends V> m) {
		this(m, DEFAULT_LOAD_FACTOR);
	}
	
Creates a new hash map copying a given type-specific one.

Params:
  • m – 
           a type-specific map to be copied into the new hash map.
  • f – 
           the load factor.
/**
	 * Creates a new hash map copying a given type-specific one.
	 *
	 * @param m
	 *            a type-specific map to be copied into the new hash map.
	 * @param f
	 *            the load factor.
	 */
	public Short2ReferenceOpenHashMap(final Short2ReferenceMap<V> m, final float f) {
		this(m.size(), f);
		putAll(m);
	}
	
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific one. 
Params:
  • m – 
           a type-specific map to be copied into the new hash map.
/**
	 * Creates a new hash map with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
	 * copying a given type-specific one.
	 *
	 * @param m
	 *            a type-specific map to be copied into the new hash map.
	 */
	public Short2ReferenceOpenHashMap(final Short2ReferenceMap<V> m) {
		this(m, DEFAULT_LOAD_FACTOR);
	}
	
Creates a new hash map using the elements of two parallel arrays.

Params:
  • k – 
           the array of keys of the new hash map.
  • v – 
           the array of corresponding values in the new hash map.
  • f – 
           the load factor.
Throws:
/**
	 * Creates a new hash map using the elements of two parallel arrays.
	 *
	 * @param k
	 *            the array of keys of the new hash map.
	 * @param v
	 *            the array of corresponding values in the new hash map.
	 * @param f
	 *            the load factor.
	 * @throws IllegalArgumentException
	 *             if {@code k} and {@code v} have different lengths.
	 */
	public Short2ReferenceOpenHashMap(final short[] k, final V[] v, final float f) {
		this(k.length, f);
		if (k.length != v.length)
			throw new IllegalArgumentException(
					"The key array and the value array have different lengths (" + k.length + " and " + v.length + ")");
		for (int i = 0; i < k.length; i++)
			this.put(k[i], v[i]);
	}
	
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor using the elements of two parallel arrays. 
Params:
  • k – 
           the array of keys of the new hash map.
  • v – 
           the array of corresponding values in the new hash map.
Throws:
/**
	 * Creates a new hash map with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
	 * using the elements of two parallel arrays.
	 *
	 * @param k
	 *            the array of keys of the new hash map.
	 * @param v
	 *            the array of corresponding values in the new hash map.
	 * @throws IllegalArgumentException
	 *             if {@code k} and {@code v} have different lengths.
	 */
	public Short2ReferenceOpenHashMap(final short[] k, final V[] v) {
		this(k, v, DEFAULT_LOAD_FACTOR);
	}
	private int realSize() {
		return containsNullKey ? 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);
	}
	private V removeEntry(final int pos) {
		final V oldValue = value[pos];
		value[pos] = null;
		size--;
		shiftKeys(pos);
		if (n > minN && size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
			rehash(n / 2);
		return oldValue;
	}
	private V removeNullEntry() {
		containsNullKey = false;
		final V oldValue = value[n];
		value[n] = null;
		size--;
		if (n > minN && size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
			rehash(n / 2);
		return oldValue;
	}
	@Override
	public void putAll(Map<? extends Short, ? extends V> m) {
		if (f <= .5)
			ensureCapacity(m.size()); // The resulting map will be sized for m.size() elements
		else
			tryCapacity(size() + m.size()); // The resulting map will be tentatively sized for size() + m.size()
											// elements
		super.putAll(m);
	}

	private int find(final short k) {
		if (((k) == ((short) 0)))
			return containsNullKey ? n : -(n + 1);
		short curr;
		final short[] key = this.key;
		int pos;
		// The starting point.
		if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
			return -(pos + 1);
		if (((k) == (curr)))
			return pos;
		// There's always an unused entry.
		while (true) {
			if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
				return -(pos + 1);
			if (((k) == (curr)))
				return pos;
		}
	}
	private void insert(final int pos, final short k, final V v) {
		if (pos == n)
			containsNullKey = true;
		key[pos] = k;
		value[pos] = v;
		if (size++ >= maxFill)
			rehash(arraySize(size + 1, f));
		if (ASSERTS)
			checkTable();
	}
	@Override
	public V put(final short k, final V v) {
		final int pos = find(k);
		if (pos < 0) {
			insert(-pos - 1, k, v);
			return defRetValue;
		}
		final V oldValue = value[pos];
		value[pos] = v;
		return oldValue;
	}
	
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;
		short curr;
		final short[] key = this.key;
		for (;;) {
			pos = ((last = pos) + 1) & mask;
			for (;;) {
				if (((curr = key[pos]) == ((short) 0))) {
					key[last] = ((short) 0);
					value[last] = null;
					return;
				}
				slot = (it.unimi.dsi.fastutil.HashCommon.mix((curr))) & mask;
				if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos)
					break;
				pos = (pos + 1) & mask;
			}
			key[last] = curr;
			value[last] = value[pos];
		}
	}
	@Override

	public V remove(final short k) {
		if (((k) == ((short) 0))) {
			if (containsNullKey)
				return removeNullEntry();
			return defRetValue;
		}
		short curr;
		final short[] key = this.key;
		int pos;
		// The starting point.
		if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
			return defRetValue;
		if (((k) == (curr)))
			return removeEntry(pos);
		while (true) {
			if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
				return defRetValue;
			if (((k) == (curr)))
				return removeEntry(pos);
		}
	}
	@Override

	public V get(final short k) {
		if (((k) == ((short) 0)))
			return containsNullKey ? value[n] : defRetValue;
		short curr;
		final short[] key = this.key;
		int pos;
		// The starting point.
		if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
			return defRetValue;
		if (((k) == (curr)))
			return value[pos];
		// There's always an unused entry.
		while (true) {
			if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
				return defRetValue;
			if (((k) == (curr)))
				return value[pos];
		}
	}
	@Override

	public boolean containsKey(final short k) {
		if (((k) == ((short) 0)))
			return containsNullKey;
		short curr;
		final short[] key = this.key;
		int pos;
		// The starting point.
		if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
			return false;
		if (((k) == (curr)))
			return true;
		// There's always an unused entry.
		while (true) {
			if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
				return false;
			if (((k) == (curr)))
				return true;
		}
	}
	@Override
	public boolean containsValue(final Object v) {
		final V value[] = this.value;
		final short key[] = this.key;
		if (containsNullKey && ((value[n]) == (v)))
			return true;
		for (int i = n; i-- != 0;)
			if (!((key[i]) == ((short) 0)) && ((value[i]) == (v)))
				return true;
		return false;
	}
	
{@inheritDoc} 
/** {@inheritDoc} */
	@Override

	public V getOrDefault(final short k, final V defaultValue) {
		if (((k) == ((short) 0)))
			return containsNullKey ? value[n] : defaultValue;
		short curr;
		final short[] key = this.key;
		int pos;
		// The starting point.
		if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
			return defaultValue;
		if (((k) == (curr)))
			return value[pos];
		// There's always an unused entry.
		while (true) {
			if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
				return defaultValue;
			if (((k) == (curr)))
				return value[pos];
		}
	}
	
{@inheritDoc} 
/** {@inheritDoc} */
	@Override
	public V putIfAbsent(final short k, final V v) {
		final int pos = find(k);
		if (pos >= 0)
			return value[pos];
		insert(-pos - 1, k, v);
		return defRetValue;
	}
	
{@inheritDoc} 
/** {@inheritDoc} */
	@Override

	public boolean remove(final short k, final Object v) {
		if (((k) == ((short) 0))) {
			if (containsNullKey && ((v) == (value[n]))) {
				removeNullEntry();
				return true;
			}
			return false;
		}
		short curr;
		final short[] key = this.key;
		int pos;
		// The starting point.
		if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
			return false;
		if (((k) == (curr)) && ((v) == (value[pos]))) {
			removeEntry(pos);
			return true;
		}
		while (true) {
			if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
				return false;
			if (((k) == (curr)) && ((v) == (value[pos]))) {
				removeEntry(pos);
				return true;
			}
		}
	}
	
{@inheritDoc} 
/** {@inheritDoc} */
	@Override
	public boolean replace(final short k, final V oldValue, final V v) {
		final int pos = find(k);
		if (pos < 0 || !((oldValue) == (value[pos])))
			return false;
		value[pos] = v;
		return true;
	}
	
{@inheritDoc} 
/** {@inheritDoc} */
	@Override
	public V replace(final short k, final V v) {
		final int pos = find(k);
		if (pos < 0)
			return defRetValue;
		final V oldValue = value[pos];
		value[pos] = v;
		return oldValue;
	}
	
{@inheritDoc} 
/** {@inheritDoc} */
	@Override
	public V computeIfAbsent(final short k, final java.util.function.IntFunction<? extends V> mappingFunction) {
		java.util.Objects.requireNonNull(mappingFunction);
		final int pos = find(k);
		if (pos >= 0)
			return value[pos];
		final V newValue = mappingFunction.apply(k);
		insert(-pos - 1, k, newValue);
		return newValue;
	}
	
{@inheritDoc} 
/** {@inheritDoc} */
	@Override
	public V computeIfPresent(final short k,
			final java.util.function.BiFunction<? super Short, ? super V, ? extends V> remappingFunction) {
		java.util.Objects.requireNonNull(remappingFunction);
		final int pos = find(k);
		if (pos < 0)
			return defRetValue;
		final V newValue = remappingFunction.apply(Short.valueOf(k), (value[pos]));
		if (newValue == null) {
			if (((k) == ((short) 0)))
				removeNullEntry();
			else
				removeEntry(pos);
			return defRetValue;
		}
		return value[pos] = (newValue);
	}
	
{@inheritDoc} 
/** {@inheritDoc} */
	@Override
	public V compute(final short k,
			final java.util.function.BiFunction<? super Short, ? super V, ? extends V> remappingFunction) {
		java.util.Objects.requireNonNull(remappingFunction);
		final int pos = find(k);
		final V newValue = remappingFunction.apply(Short.valueOf(k), pos >= 0 ? (value[pos]) : null);
		if (newValue == null) {
			if (pos >= 0) {
				if (((k) == ((short) 0)))
					removeNullEntry();
				else
					removeEntry(pos);
			}
			return defRetValue;
		}
		V newVal = (newValue);
		if (pos < 0) {
			insert(-pos - 1, k, newVal);
			return newVal;
		}
		return value[pos] = newVal;
	}
	
{@inheritDoc} 
/** {@inheritDoc} */
	@Override
	public V merge(final short k, final V v,
			final java.util.function.BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
		java.util.Objects.requireNonNull(remappingFunction);
		final int pos = find(k);
		if (pos < 0 || value[pos] == null) {
			if (v == null)
				return defRetValue;
			insert(-pos - 1, k, v);
			return v;
		}
		final V newValue = remappingFunction.apply((value[pos]), (v));
		if (newValue == null) {
			if (((k) == ((short) 0)))
				removeNullEntry();
			else
				removeEntry(pos);
			return defRetValue;
		}
		return value[pos] = (newValue);
	}
	/*
	 * Removes all elements from this map.
	 *
	 * <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;
		containsNullKey = false;
		Arrays.fill(key, ((short) 0));
		Arrays.fill(value, null);
	}
	@Override
	public int size() {
		return size;
	}
	@Override
	public boolean isEmpty() {
		return size == 0;
	}
	
The entry class for a hash map does not record key and value, but rather the position in the hash table of the corresponding entry. This is necessary so that calls to Entry.setValue(Object) are reflected in the map 
/**
	 * The entry class for a hash map does not record key and value, but rather the
	 * position in the hash table of the corresponding entry. This is necessary so
	 * that calls to {@link java.util.Map.Entry#setValue(Object)} are reflected in
	 * the map
	 */
	final class MapEntry implements Short2ReferenceMap.Entry<V>, Map.Entry<Short, V> {
		// The table index this entry refers to, or -1 if this entry has been deleted.
		int index;
		MapEntry(final int index) {
			this.index = index;
		}
		MapEntry() {
		}
		@Override
		public short getShortKey() {
			return key[index];
		}
		@Override
		public V getValue() {
			return value[index];
		}
		@Override
		public V setValue(final V v) {
			final V oldValue = value[index];
			value[index] = v;
			return oldValue;
		}
		
{@inheritDoc}

Deprecated:Please use the corresponding type-specific method instead.
/**
		 * {@inheritDoc}
		 * 
		 * @deprecated Please use the corresponding type-specific method instead.
		 */
		@Deprecated
		@Override
		public Short getKey() {
			return Short.valueOf(key[index]);
		}
		@SuppressWarnings("unchecked")
		@Override
		public boolean equals(final Object o) {
			if (!(o instanceof Map.Entry))
				return false;
			Map.Entry<Short, V> e = (Map.Entry<Short, V>) o;
			return ((key[index]) == ((e.getKey()).shortValue())) && ((value[index]) == ((e.getValue())));
		}
		@Override
		public int hashCode() {
			return (key[index]) ^ ((value[index]) == null ? 0 : System.identityHashCode(value[index]));
		}
		@Override
		public String toString() {
			return key[index] + "=>" + value[index];
		}
	}
	
An iterator over a hash map. 
/** An iterator over a hash map. */
	private class MapIterator {
		
The index of the last entry returned, if positive or zero; initially, Short2ReferenceOpenHashMap<V>.n. If negative, the last entry returned was that of the key of index - pos - 1 from the MapIterator.wrapped list. 
/**
		 * The index of the last entry returned, if positive or zero; initially,
		 * {@link #n}. If negative, the last entry returned was that of the key 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 MapIterator.pos if MapIterator.pos is positive, or Integer.MIN_VALUE if MapIterator.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 entry with the null key.

/**
		 * A boolean telling us whether we should return the entry with the null key.
		 */
		boolean mustReturnNullKey = Short2ReferenceOpenHashMap.this.containsNullKey;
		
A lazily allocated list containing keys of entries that have wrapped around
the table because of removals.

/**
		 * A lazily allocated list containing keys of entries that have wrapped around
		 * the table because of removals.
		 */
		ShortArrayList wrapped;
		public boolean hasNext() {
			return c != 0;
		}
		public int nextEntry() {
			if (!hasNext())
				throw new NoSuchElementException();
			c--;
			if (mustReturnNullKey) {
				mustReturnNullKey = false;
				return last = n;
			}
			final short key[] = Short2ReferenceOpenHashMap.this.key;
			for (;;) {
				if (--pos < 0) {
					// We are just enumerating elements from the wrapped list.
					last = Integer.MIN_VALUE;
					final short k = wrapped.getShort(-pos - 1);
					int p = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask;
					while (!((k) == (key[p])))
						p = (p + 1) & mask;
					return p;
				}
				if (!((key[pos]) == ((short) 0)))
					return 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 void shiftKeys(int pos) {
			// Shift entries with the same hash.
			int last, slot;
			short curr;
			final short[] key = Short2ReferenceOpenHashMap.this.key;
			for (;;) {
				pos = ((last = pos) + 1) & mask;
				for (;;) {
					if (((curr = key[pos]) == ((short) 0))) {
						key[last] = ((short) 0);
						value[last] = null;
						return;
					}
					slot = (it.unimi.dsi.fastutil.HashCommon.mix((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 ShortArrayList(2);
					wrapped.add(key[pos]);
				}
				key[last] = curr;
				value[last] = value[pos];
			}
		}
		public void remove() {
			if (last == -1)
				throw new IllegalStateException();
			if (last == n) {
				containsNullKey = false;
				value[n] = null;
			} else if (pos >= 0)
				shiftKeys(last);
			else {
				// We're removing wrapped entries.
				Short2ReferenceOpenHashMap.this.remove(wrapped.getShort(-pos - 1));
				last = -1; // Note that we must not decrement size
				return;
			}
			size--;
			last = -1; // You can no longer remove this entry.
			if (ASSERTS)
				checkTable();
		}
		public int skip(final int n) {
			int i = n;
			while (i-- != 0 && hasNext())
				nextEntry();
			return n - i - 1;
		}
	}
	private class EntryIterator extends MapIterator implements ObjectIterator<Short2ReferenceMap.Entry<V>> {
		private MapEntry entry;
		@Override
		public MapEntry next() {
			return entry = new MapEntry(nextEntry());
		}
		@Override
		public void remove() {
			super.remove();
			entry.index = -1; // You cannot use a deleted entry.
		}
	}
	private class FastEntryIterator extends MapIterator implements ObjectIterator<Short2ReferenceMap.Entry<V>> {
		private final MapEntry entry = new MapEntry();
		@Override
		public MapEntry next() {
			entry.index = nextEntry();
			return entry;
		}
	}
	private final class MapEntrySet extends AbstractObjectSet<Short2ReferenceMap.Entry<V>> implements FastEntrySet<V> {
		@Override
		public ObjectIterator<Short2ReferenceMap.Entry<V>> iterator() {
			return new EntryIterator();
		}
		@Override
		public ObjectIterator<Short2ReferenceMap.Entry<V>> fastIterator() {
			return new FastEntryIterator();
		}
		@Override
		@SuppressWarnings("unchecked")
		public boolean contains(final Object o) {
			if (!(o instanceof Map.Entry))
				return false;
			final Map.Entry<?, ?> e = (Map.Entry<?, ?>) o;
			if (e.getKey() == null || !(e.getKey() instanceof Short))
				return false;
			final short k = ((Short) (e.getKey())).shortValue();
			final V v = ((V) e.getValue());
			if (((k) == ((short) 0)))
				return Short2ReferenceOpenHashMap.this.containsNullKey && ((value[n]) == (v));
			short curr;
			final short[] key = Short2ReferenceOpenHashMap.this.key;
			int pos;
			// The starting point.
			if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
				return false;
			if (((k) == (curr)))
				return ((value[pos]) == (v));
			// There's always an unused entry.
			while (true) {
				if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
					return false;
				if (((k) == (curr)))
					return ((value[pos]) == (v));
			}
		}
		@Override
		@SuppressWarnings("unchecked")
		public boolean remove(final Object o) {
			if (!(o instanceof Map.Entry))
				return false;
			final Map.Entry<?, ?> e = (Map.Entry<?, ?>) o;
			if (e.getKey() == null || !(e.getKey() instanceof Short))
				return false;
			final short k = ((Short) (e.getKey())).shortValue();
			final V v = ((V) e.getValue());
			if (((k) == ((short) 0))) {
				if (containsNullKey && ((value[n]) == (v))) {
					removeNullEntry();
					return true;
				}
				return false;
			}
			short curr;
			final short[] key = Short2ReferenceOpenHashMap.this.key;
			int pos;
			// The starting point.
			if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
				return false;
			if (((curr) == (k))) {
				if (((value[pos]) == (v))) {
					removeEntry(pos);
					return true;
				}
				return false;
			}
			while (true) {
				if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
					return false;
				if (((curr) == (k))) {
					if (((value[pos]) == (v))) {
						removeEntry(pos);
						return true;
					}
				}
			}
		}
		@Override
		public int size() {
			return size;
		}
		@Override
		public void clear() {
			Short2ReferenceOpenHashMap.this.clear();
		}
		
{@inheritDoc} 
/** {@inheritDoc} */
		@Override
		public void forEach(final Consumer<? super Short2ReferenceMap.Entry<V>> consumer) {
			if (containsNullKey)
				consumer.accept(new AbstractShort2ReferenceMap.BasicEntry<V>(key[n], value[n]));
			for (int pos = n; pos-- != 0;)
				if (!((key[pos]) == ((short) 0)))
					consumer.accept(new AbstractShort2ReferenceMap.BasicEntry<V>(key[pos], value[pos]));
		}
		
{@inheritDoc} 
/** {@inheritDoc} */
		@Override
		public void fastForEach(final Consumer<? super Short2ReferenceMap.Entry<V>> consumer) {
			final AbstractShort2ReferenceMap.BasicEntry<V> entry = new AbstractShort2ReferenceMap.BasicEntry<>();
			if (containsNullKey) {
				entry.key = key[n];
				entry.value = value[n];
				consumer.accept(entry);
			}
			for (int pos = n; pos-- != 0;)
				if (!((key[pos]) == ((short) 0))) {
					entry.key = key[pos];
					entry.value = value[pos];
					consumer.accept(entry);
				}
		}
	}
	@Override
	public FastEntrySet<V> short2ReferenceEntrySet() {
		if (entries == null)
			entries = new MapEntrySet();
		return entries;
	}
	
An iterator on keys.

 We simply override the ListIterator.next()/ListIterator.previous() methods (and possibly their type-specific counterparts) so that they return keys instead of entries. 
/**
	 * An iterator on keys.
	 *
	 * <p>
	 * We simply override the
	 * {@link java.util.ListIterator#next()}/{@link java.util.ListIterator#previous()}
	 * methods (and possibly their type-specific counterparts) so that they return
	 * keys instead of entries.
	 */
	private final class KeyIterator extends MapIterator implements ShortIterator {
		public KeyIterator() {
			super();
		}
		@Override
		public short nextShort() {
			return key[nextEntry()];
		}
	}
	private final class KeySet extends AbstractShortSet {
		@Override
		public ShortIterator iterator() {
			return new KeyIterator();
		}
		
{@inheritDoc} 
/** {@inheritDoc} */
		@Override
		public void forEach(final java.util.function.IntConsumer consumer) {
			if (containsNullKey)
				consumer.accept(key[n]);
			for (int pos = n; pos-- != 0;) {
				final short k = key[pos];
				if (!((k) == ((short) 0)))
					consumer.accept(k);
			}
		}
		@Override
		public int size() {
			return size;
		}
		@Override
		public boolean contains(short k) {
			return containsKey(k);
		}
		@Override
		public boolean remove(short k) {
			final int oldSize = size;
			Short2ReferenceOpenHashMap.this.remove(k);
			return size != oldSize;
		}
		@Override
		public void clear() {
			Short2ReferenceOpenHashMap.this.clear();
		}
	}
	@Override
	public ShortSet keySet() {
		if (keys == null)
			keys = new KeySet();
		return keys;
	}
	
An iterator on values.

 We simply override the ListIterator.next()/ListIterator.previous() methods (and possibly their type-specific counterparts) so that they return values instead of entries. 
/**
	 * An iterator on values.
	 *
	 * <p>
	 * We simply override the
	 * {@link java.util.ListIterator#next()}/{@link java.util.ListIterator#previous()}
	 * methods (and possibly their type-specific counterparts) so that they return
	 * values instead of entries.
	 */
	private final class ValueIterator extends MapIterator implements ObjectIterator<V> {
		public ValueIterator() {
			super();
		}
		@Override
		public V next() {
			return value[nextEntry()];
		}
	}
	@Override
	public ReferenceCollection<V> values() {
		if (values == null)
			values = new AbstractReferenceCollection<V>() {
				@Override
				public ObjectIterator<V> iterator() {
					return new ValueIterator();
				}
				@Override
				public int size() {
					return size;
				}
				@Override
				public boolean contains(Object v) {
					return containsValue(v);
				}
				@Override
				public void clear() {
					Short2ReferenceOpenHashMap.this.clear();
				}
				
{@inheritDoc} 
/** {@inheritDoc} */
				@Override
				public void forEach(final Consumer<? super V> consumer) {
					if (containsNullKey)
						consumer.accept(value[n]);
					for (int pos = n; pos-- != 0;)
						if (!((key[pos]) == ((short) 0)))
							consumer.accept(value[pos]);
				}
			};
		return values;
	}
	
Rehashes the map, 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:
Returns:true if there was enough memory to trim the map.
/**
	 * Rehashes the map, 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 map.
	 * @see #trim(int)
	 */
	public boolean trim() {
		return trim(size);
	}
	
Rehashes this map 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 map in a table of size
N.

 This method is useful when reusing maps. Clearing a map leaves the table size untouched. If you are reusing a map 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 maps. 
Params:
  • n – 
           the threshold for the trimming.
See Also:
Returns:true if there was enough memory to trim the map.
/**
	 * Rehashes this map 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 map in a table of size
	 * <var>N</var>.
	 *
	 * <p>
	 * This method is useful when reusing maps. {@linkplain #clear() Clearing a map}
	 * leaves the table size untouched. If you are reusing a map 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 maps.
	 *
	 * @param n
	 *            the threshold for the trimming.
	 * @return true if there was enough memory to trim the map.
	 * @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 map.


This method implements the basic rehashing strategy, and may be overridden 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 map.
	 *
	 * <p>
	 * This method implements the basic rehashing strategy, and may be overridden 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 short key[] = this.key;
		final V value[] = this.value;
		final int mask = newN - 1; // Note that this is used by the hashing macro
		final short newKey[] = new short[newN + 1];
		final V newValue[] = (V[]) new Object[newN + 1];
		int i = n, pos;
		for (int j = realSize(); j-- != 0;) {
			while (((key[--i]) == ((short) 0)));
			if (!((newKey[pos = (it.unimi.dsi.fastutil.HashCommon.mix((key[i]))) & mask]) == ((short) 0)))
				while (!((newKey[pos = (pos + 1) & mask]) == ((short) 0)));
			newKey[pos] = key[i];
			newValue[pos] = value[i];
		}
		newValue[newN] = value[n];
		n = newN;
		this.mask = mask;
		maxFill = maxFill(n, f);
		this.key = newKey;
		this.value = newValue;
	}
	
Returns a deep copy of this map.


This method performs a deep copy of this hash map; the data stored in the
map, however, is not cloned. Note that this makes a difference only for
object keys.

Returns:a deep copy of this map.
/**
	 * Returns a deep copy of this map.
	 *
	 * <p>
	 * This method performs a deep copy of this hash map; the data stored in the
	 * map, however, is not cloned. Note that this makes a difference only for
	 * object keys.
	 *
	 * @return a deep copy of this map.
	 */
	@Override
	@SuppressWarnings("unchecked")
	public Short2ReferenceOpenHashMap<V> clone() {
		Short2ReferenceOpenHashMap<V> c;
		try {
			c = (Short2ReferenceOpenHashMap<V>) super.clone();
		} catch (CloneNotSupportedException cantHappen) {
			throw new InternalError();
		}
		c.keys = null;
		c.values = null;
		c.entries = null;
		c.containsNullKey = containsNullKey;
		c.key = key.clone();
		c.value = value.clone();
		return c;
	}
	
Returns a hash code for this map. 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 map.
/**
	 * Returns a hash code for this map.
	 *
	 * 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 map.
	 */
	@Override
	public int hashCode() {
		int h = 0;
		for (int j = realSize(), i = 0, t = 0; j-- != 0;) {
			while (((key[i]) == ((short) 0)))
				i++;
			t = (key[i]);
			if (this != value[i])
				t ^= ((value[i]) == null ? 0 : System.identityHashCode(value[i]));
			h += t;
			i++;
		}
		// Zero / null keys have hash zero.
		if (containsNullKey)
			h += ((value[n]) == null ? 0 : System.identityHashCode(value[n]));
		return h;
	}
	private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
		final short key[] = this.key;
		final V value[] = this.value;
		final MapIterator i = new MapIterator();
		s.defaultWriteObject();
		for (int j = size, e; j-- != 0;) {
			e = i.nextEntry();
			s.writeShort(key[e]);
			s.writeObject(value[e]);
		}
	}
	@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 short key[] = this.key = new short[n + 1];
		final V value[] = this.value = (V[]) new Object[n + 1];
		short k;
		V v;
		for (int i = size, pos; i-- != 0;) {
			k = s.readShort();
			v = (V) s.readObject();
			if (((k) == ((short) 0))) {
				pos = n;
				containsNullKey = true;
			} else {
				pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask;
				while (!((key[pos]) == ((short) 0)))
					pos = (pos + 1) & mask;
			}
			key[pos] = k;
			value[pos] = v;
		}
		if (ASSERTS)
			checkTable();
	}
	private void checkTable() {
	}
}