All Known Implementing Classes:

BooleanOpenHashSet, Byte2BooleanLinkedOpenHashMap, Byte2BooleanOpenCustomHashMap, Byte2BooleanOpenHashMap, Byte2ByteLinkedOpenHashMap, Byte2ByteOpenCustomHashMap, Byte2ByteOpenHashMap, Byte2CharLinkedOpenHashMap, Byte2CharOpenCustomHashMap, Byte2CharOpenHashMap, Byte2DoubleLinkedOpenHashMap, Byte2DoubleOpenCustomHashMap, Byte2DoubleOpenHashMap, Byte2FloatLinkedOpenHashMap, Byte2FloatOpenCustomHashMap, Byte2FloatOpenHashMap, Byte2IntLinkedOpenHashMap, Byte2IntOpenCustomHashMap, Byte2IntOpenHashMap, Byte2LongLinkedOpenHashMap, Byte2LongOpenCustomHashMap, Byte2LongOpenHashMap, Byte2ObjectLinkedOpenHashMap, Byte2ObjectOpenCustomHashMap, Byte2ObjectOpenHashMap, Byte2ReferenceLinkedOpenHashMap, Byte2ReferenceOpenCustomHashMap, Byte2ReferenceOpenHashMap, Byte2ShortLinkedOpenHashMap, Byte2ShortOpenCustomHashMap, Byte2ShortOpenHashMap, ByteLinkedOpenCustomHashSet, ByteLinkedOpenHashSet, ByteOpenCustomHashSet, ByteOpenHashSet, Char2BooleanLinkedOpenHashMap, Char2BooleanOpenCustomHashMap, Char2BooleanOpenHashMap, Char2ByteLinkedOpenHashMap, Char2ByteOpenCustomHashMap, Char2ByteOpenHashMap, Char2CharLinkedOpenHashMap, Char2CharOpenCustomHashMap, Char2CharOpenHashMap, Char2DoubleLinkedOpenHashMap, Char2DoubleOpenCustomHashMap, Char2DoubleOpenHashMap, Char2FloatLinkedOpenHashMap, Char2FloatOpenCustomHashMap, Char2FloatOpenHashMap, Char2IntLinkedOpenHashMap, Char2IntOpenCustomHashMap, Char2IntOpenHashMap, Char2LongLinkedOpenHashMap, Char2LongOpenCustomHashMap, Char2LongOpenHashMap, Char2ObjectLinkedOpenHashMap, Char2ObjectOpenCustomHashMap, Char2ObjectOpenHashMap, Char2ReferenceLinkedOpenHashMap, Char2ReferenceOpenCustomHashMap, Char2ReferenceOpenHashMap, Char2ShortLinkedOpenHashMap, Char2ShortOpenCustomHashMap, Char2ShortOpenHashMap, CharLinkedOpenCustomHashSet, CharLinkedOpenHashSet, CharOpenCustomHashSet, CharOpenHashSet, Double2BooleanLinkedOpenHashMap, Double2BooleanOpenCustomHashMap, Double2BooleanOpenHashMap, Double2ByteLinkedOpenHashMap, Double2ByteOpenCustomHashMap, Double2ByteOpenHashMap, Double2CharLinkedOpenHashMap, Double2CharOpenCustomHashMap, Double2CharOpenHashMap, Double2DoubleLinkedOpenHashMap, Double2DoubleOpenCustomHashMap, Double2DoubleOpenHashMap, Double2FloatLinkedOpenHashMap, Double2FloatOpenCustomHashMap, Double2FloatOpenHashMap, Double2IntLinkedOpenHashMap, Double2IntOpenCustomHashMap, Double2IntOpenHashMap, Double2LongLinkedOpenHashMap, Double2LongOpenCustomHashMap, Double2LongOpenHashMap, Double2ObjectLinkedOpenHashMap, Double2ObjectOpenCustomHashMap, Double2ObjectOpenHashMap, Double2ReferenceLinkedOpenHashMap, Double2ReferenceOpenCustomHashMap, Double2ReferenceOpenHashMap, Double2ShortLinkedOpenHashMap, Double2ShortOpenCustomHashMap, Double2ShortOpenHashMap, DoubleLinkedOpenCustomHashSet, DoubleLinkedOpenHashSet, DoubleOpenCustomHashSet, DoubleOpenHashBigSet, DoubleOpenHashSet, Float2BooleanLinkedOpenHashMap, Float2BooleanOpenCustomHashMap, Float2BooleanOpenHashMap, Float2ByteLinkedOpenHashMap, Float2ByteOpenCustomHashMap, Float2ByteOpenHashMap, Float2CharLinkedOpenHashMap, Float2CharOpenCustomHashMap, Float2CharOpenHashMap, Float2DoubleLinkedOpenHashMap, Float2DoubleOpenCustomHashMap, Float2DoubleOpenHashMap, Float2FloatLinkedOpenHashMap, Float2FloatOpenCustomHashMap, Float2FloatOpenHashMap, Float2IntLinkedOpenHashMap, Float2IntOpenCustomHashMap, Float2IntOpenHashMap, Float2LongLinkedOpenHashMap, Float2LongOpenCustomHashMap, Float2LongOpenHashMap, Float2ObjectLinkedOpenHashMap, Float2ObjectOpenCustomHashMap, Float2ObjectOpenHashMap, Float2ReferenceLinkedOpenHashMap, Float2ReferenceOpenCustomHashMap, Float2ReferenceOpenHashMap, Float2ShortLinkedOpenHashMap, Float2ShortOpenCustomHashMap, Float2ShortOpenHashMap, FloatLinkedOpenCustomHashSet, FloatLinkedOpenHashSet, FloatOpenCustomHashSet, FloatOpenHashBigSet, FloatOpenHashSet, Int2BooleanLinkedOpenHashMap, Int2BooleanOpenCustomHashMap, Int2BooleanOpenHashMap, Int2ByteLinkedOpenHashMap, Int2ByteOpenCustomHashMap, Int2ByteOpenHashMap, Int2CharLinkedOpenHashMap, Int2CharOpenCustomHashMap, Int2CharOpenHashMap, Int2DoubleLinkedOpenHashMap, Int2DoubleOpenCustomHashMap, Int2DoubleOpenHashMap, Int2FloatLinkedOpenHashMap, Int2FloatOpenCustomHashMap, Int2FloatOpenHashMap, Int2IntLinkedOpenHashMap, Int2IntOpenCustomHashMap, Int2IntOpenHashMap, Int2LongLinkedOpenHashMap, Int2LongOpenCustomHashMap, Int2LongOpenHashMap, Int2ObjectLinkedOpenHashMap, Int2ObjectOpenCustomHashMap, Int2ObjectOpenHashMap, Int2ReferenceLinkedOpenHashMap, Int2ReferenceOpenCustomHashMap, Int2ReferenceOpenHashMap, Int2ShortLinkedOpenHashMap, Int2ShortOpenCustomHashMap, Int2ShortOpenHashMap, IntLinkedOpenCustomHashSet, IntLinkedOpenHashSet, IntOpenCustomHashSet, IntOpenHashBigSet, IntOpenHashSet, Long2BooleanLinkedOpenHashMap, Long2BooleanOpenCustomHashMap, Long2BooleanOpenHashMap, Long2ByteLinkedOpenHashMap, Long2ByteOpenCustomHashMap, Long2ByteOpenHashMap, Long2CharLinkedOpenHashMap, Long2CharOpenCustomHashMap, Long2CharOpenHashMap, Long2DoubleLinkedOpenHashMap, Long2DoubleOpenCustomHashMap, Long2DoubleOpenHashMap, Long2FloatLinkedOpenHashMap, Long2FloatOpenCustomHashMap, Long2FloatOpenHashMap, Long2IntLinkedOpenHashMap, Long2IntOpenCustomHashMap, Long2IntOpenHashMap, Long2LongLinkedOpenHashMap, Long2LongOpenCustomHashMap, Long2LongOpenHashMap, Long2ObjectLinkedOpenHashMap, Long2ObjectOpenCustomHashMap, Long2ObjectOpenHashMap, Long2ReferenceLinkedOpenHashMap, Long2ReferenceOpenCustomHashMap, Long2ReferenceOpenHashMap, Long2ShortLinkedOpenHashMap, Long2ShortOpenCustomHashMap, Long2ShortOpenHashMap, LongLinkedOpenCustomHashSet, LongLinkedOpenHashSet, LongOpenCustomHashSet, LongOpenHashBigSet, LongOpenHashSet, Object2BooleanLinkedOpenCustomHashMap, Object2BooleanLinkedOpenHashMap, Object2BooleanOpenCustomHashMap, Object2BooleanOpenHashMap, Object2ByteLinkedOpenCustomHashMap, Object2ByteLinkedOpenHashMap, Object2ByteOpenCustomHashMap, Object2ByteOpenHashMap, Object2CharLinkedOpenCustomHashMap, Object2CharLinkedOpenHashMap, Object2CharOpenCustomHashMap, Object2CharOpenHashMap, Object2DoubleLinkedOpenCustomHashMap, Object2DoubleLinkedOpenHashMap, Object2DoubleOpenCustomHashMap, Object2DoubleOpenHashMap, Object2FloatLinkedOpenCustomHashMap, Object2FloatLinkedOpenHashMap, Object2FloatOpenCustomHashMap, Object2FloatOpenHashMap, Object2IntLinkedOpenCustomHashMap, Object2IntLinkedOpenHashMap, Object2IntOpenCustomHashMap, Object2IntOpenHashMap, Object2LongLinkedOpenCustomHashMap, Object2LongLinkedOpenHashMap, Object2LongOpenCustomHashMap, Object2LongOpenHashMap, Object2ObjectLinkedOpenCustomHashMap, Object2ObjectLinkedOpenHashMap, Object2ObjectOpenCustomHashMap, Object2ObjectOpenHashMap, Object2ReferenceLinkedOpenCustomHashMap, Object2ReferenceLinkedOpenHashMap, Object2ReferenceOpenCustomHashMap, Object2ReferenceOpenHashMap, Object2ShortLinkedOpenCustomHashMap, Object2ShortLinkedOpenHashMap, Object2ShortOpenCustomHashMap, Object2ShortOpenHashMap, ObjectLinkedOpenCustomHashSet, ObjectLinkedOpenHashSet, ObjectOpenCustomHashSet, ObjectOpenHashBigSet, ObjectOpenHashSet, Reference2BooleanLinkedOpenHashMap, Reference2BooleanOpenCustomHashMap, Reference2BooleanOpenHashMap, Reference2ByteLinkedOpenHashMap, Reference2ByteOpenCustomHashMap, Reference2ByteOpenHashMap, Reference2CharLinkedOpenHashMap, Reference2CharOpenCustomHashMap, Reference2CharOpenHashMap, Reference2DoubleLinkedOpenHashMap, Reference2DoubleOpenCustomHashMap, Reference2DoubleOpenHashMap, Reference2FloatLinkedOpenHashMap, Reference2FloatOpenCustomHashMap, Reference2FloatOpenHashMap, Reference2IntLinkedOpenHashMap, Reference2IntOpenCustomHashMap, Reference2IntOpenHashMap, Reference2LongLinkedOpenHashMap, Reference2LongOpenCustomHashMap, Reference2LongOpenHashMap, Reference2ObjectLinkedOpenHashMap, Reference2ObjectOpenCustomHashMap, Reference2ObjectOpenHashMap, Reference2ReferenceLinkedOpenHashMap, Reference2ReferenceOpenCustomHashMap, Reference2ReferenceOpenHashMap, Reference2ShortLinkedOpenHashMap, Reference2ShortOpenCustomHashMap, Reference2ShortOpenHashMap, ReferenceLinkedOpenHashSet, ReferenceOpenHashBigSet, ReferenceOpenHashSet, Short2BooleanLinkedOpenHashMap, Short2BooleanOpenCustomHashMap, Short2BooleanOpenHashMap, Short2ByteLinkedOpenHashMap, Short2ByteOpenCustomHashMap, Short2ByteOpenHashMap, Short2CharLinkedOpenHashMap, Short2CharOpenCustomHashMap, Short2CharOpenHashMap, Short2DoubleLinkedOpenHashMap, Short2DoubleOpenCustomHashMap, Short2DoubleOpenHashMap, Short2FloatLinkedOpenHashMap, Short2FloatOpenCustomHashMap, Short2FloatOpenHashMap, Short2IntLinkedOpenHashMap, Short2IntOpenCustomHashMap, Short2IntOpenHashMap, Short2LongLinkedOpenHashMap, Short2LongOpenCustomHashMap, Short2LongOpenHashMap, Short2ObjectLinkedOpenHashMap, Short2ObjectOpenCustomHashMap, Short2ObjectOpenHashMap, Short2ReferenceLinkedOpenHashMap, Short2ReferenceOpenCustomHashMap, Short2ReferenceOpenHashMap, Short2ShortLinkedOpenHashMap, Short2ShortOpenCustomHashMap, Short2ShortOpenHashMap, ShortLinkedOpenCustomHashSet, ShortLinkedOpenHashSet, ShortOpenCustomHashSet, ShortOpenHashSet
```
public interface Hash
```
Basic data for all hash-based classes.
Historical note

Warning: the following comments are here for historical reasons, and apply just to the double hash classes that can be optionally generated. The standard fastutil distribution since 6.1.0 uses linear-probing hash tables, and tables are always sized as powers of two.
The classes in fastutil are built around open-addressing hashing implemented via double hashing. Following Knuth's suggestions in the third volume of The Art of Computer Programming, we use for the table size a prime p such that p-2 is also prime. In this way hashing is implemented with modulo p, and secondary hashing with modulo p-2.
Entries in a table can be in three states: FREE, OCCUPIED or REMOVED. The naive handling of removed entries requires that you search for a free entry as if they were occupied. However, fastutil implements two useful optimizations, based on the following invariant:
Let i₀, i₁, …, i_p-1 be the permutation of the table indices induced by the key k, that is, i₀ is the hash of k and the following indices are obtained by adding (modulo p) the secondary hash plus one. If there is a OCCUPIED entry with key k, its index in the sequence above comes before the indices of any REMOVED entries with key k.

When we search for the key k we scan the entries in the sequence i₀, i₁, …, i_p-1 and stop when k is found, when we finished the sequence or when we find a FREE entry. Note that the correctness of this procedure it is not completely trivial. Indeed, when we stop at a REMOVED entry with key k we must rely on the invariant to be sure that no OCCUPIED entry with the same key can appear later. If we insert and remove frequently the same entries, this optimization can be very effective (note, however, that when using objects as keys or values deleted entries are set to a special fixed value to optimize garbage collection).
Moreover, during the probe we keep the index of the first REMOVED entry we meet. If we actually have to insert a new element, we use that entry if we can, thus avoiding to pollute another FREE entry. Since this position comes a fortiori before any REMOVED entries with the same key, we are also keeping the invariant true.

Nested Class Summary

Nested Classes
Modifier and Type Interface Description

static interface Hash.Strategy<K>
A generic hash strategy.

Field Summary

Fields
Modifier and Type	Field	Description
`static int`	`DEFAULT_GROWTH_FACTOR`	Deprecated.
`static int`	`DEFAULT_INITIAL_SIZE`	The initial default size of a hash table.
`static float`	`DEFAULT_LOAD_FACTOR`	The default load factor of a hash table.
`static float`	`FAST_LOAD_FACTOR`	The load factor for a (usually small) table that is meant to be particularly fast.
`static byte`	`FREE`	Deprecated.
`static byte`	`OCCUPIED`	Deprecated.
`static int[]`	`PRIMES`	Deprecated.
`static byte`	`REMOVED`	Deprecated.
`static float`	`VERY_FAST_LOAD_FACTOR`	The load factor for a (usually very small) table that is meant to be extremely fast.

- Field Detail
  - DEFAULT_INITIAL_SIZE
```
static final int DEFAULT_INITIAL_SIZE
```
    The initial default size of a hash table.
    
    See Also:
    
    Constant Field Values
  - DEFAULT_LOAD_FACTOR
```
static final float DEFAULT_LOAD_FACTOR
```
    The default load factor of a hash table.
    
    See Also:
    
    Constant Field Values
  - FAST_LOAD_FACTOR
```
static final float FAST_LOAD_FACTOR
```
    The load factor for a (usually small) table that is meant to be particularly fast.
    
    See Also:
    
    Constant Field Values
  - VERY_FAST_LOAD_FACTOR
```
static final float VERY_FAST_LOAD_FACTOR
```
    The load factor for a (usually very small) table that is meant to be extremely fast.
    
    See Also:
    
    Constant Field Values
  - DEFAULT_GROWTH_FACTOR
```
@Deprecated
static final int DEFAULT_GROWTH_FACTOR
```
    Deprecated.
    
    The default growth factor of a hash table.
    
    See Also:
    
    Constant Field Values
  - FREE
```
@Deprecated
static final byte FREE
```
    Deprecated.
    
    The state of a free hash table entry.
    
    See Also:
    
    Constant Field Values
  - OCCUPIED
```
@Deprecated
static final byte OCCUPIED
```
    Deprecated.
    
    The state of a occupied hash table entry.
    
    See Also:
    
    Constant Field Values
  - REMOVED
```
@Deprecated
static final byte REMOVED
```
    Deprecated.
    
    The state of a hash table entry freed by a deletion.
    
    See Also:
    
    Constant Field Values
  - PRIMES
```
@Deprecated
static final int[] PRIMES
```
    Deprecated.
    
    A list of primes to be used as table sizes. The i-th element is the largest prime p smaller than 2^(i+28)/16 and such that p-2 is also prime (or 1, for the first few entries).

Interface Hash

Historical note

Nested Class Summary

Field Summary

Field Detail

DEFAULT_INITIAL_SIZE

DEFAULT_LOAD_FACTOR

FAST_LOAD_FACTOR

VERY_FAST_LOAD_FACTOR

DEFAULT_GROWTH_FACTOR

FREE

OCCUPIED

REMOVED

PRIMES