IdentityMap

java.lang.Object
- com.esotericsoftware.kryo.util.IdentityMap<K,V>

```
public class IdentityMap<K,V>
extends java.lang.Object
```
An unordered map that uses identity comparison for keys. This implementation is a cuckoo hash map using 3 hashes, random walking, and a small stash for problematic keys. Null keys are not allowed. Null values are allowed. No allocation is done except when growing the table size.

This map performs very fast get, containsKey, and remove (typically O(1), worst case O(log(n))). Put may be a bit slower, depending on hash collisions. Load factors greater than 0.91 greatly increase the chances the map will have to rehash to the next higher POT size.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`IdentityMap.Entries<K,V>`
`static class`	`IdentityMap.Entry<K,V>`
`static class`	`IdentityMap.Keys<K>`
`private static class`	`IdentityMap.MapIterator<K,V>`
`static class`	`IdentityMap.Values<V>`

Field Summary

Fields
Modifier and Type	Field and Description
`(package private) int`	`capacity`
`private IdentityMap.Entries`	`entries`
`private int`	`hashShift`
`private IdentityMap.Keys`	`keys`
`(package private) K[]`	`keyTable`
`private float`	`loadFactor`
`private int`	`mask`
`private static int`	`PRIME1`
`private static int`	`PRIME2`
`private static int`	`PRIME3`
`private int`	`pushIterations`
`int`	`size`
`private int`	`stashCapacity`
`(package private) int`	`stashSize`
`private int`	`threshold`
`private IdentityMap.Values`	`values`
`(package private) V[]`	`valueTable`

Constructor Summary

Constructors
Constructor and Description
`IdentityMap()` Creates a new map with an initial capacity of 32 and a load factor of 0.8.
`IdentityMap(int initialCapacity)` Creates a new map with a load factor of 0.8.
`IdentityMap(int initialCapacity, float loadFactor)` Creates a new map with the specified initial capacity and load factor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`clear()`
`void`	`clear(int maximumCapacity)` Clears the map and reduces the size of the backing arrays to be the specified capacity if they are larger.
`boolean`	`containsKey(K key)`
`private boolean`	`containsKeyStash(K key)`
`boolean`	`containsValue(java.lang.Object value, boolean identity)` Returns true if the specified value is in the map.
`void`	`ensureCapacity(int additionalCapacity)` Increases the size of the backing array to acommodate the specified number of additional items.
`IdentityMap.Entries<K,V>`	`entries()` Returns an iterator for the entries in the map.
`K`	`findKey(java.lang.Object value, boolean identity)` Returns the key for the specified value, or null if it is not in the map.
`V`	`get(K key)`
`V`	`get(K key, V defaultValue)`
`private V`	`getStash(K key, V defaultValue)`
`private int`	`hash2(int h)`
`private int`	`hash3(int h)`
`IdentityMap.Keys<K>`	`keys()` Returns an iterator for the keys in the map.
`private void`	`push(K insertKey, V insertValue, int index1, K key1, int index2, K key2, int index3, K key3)`
`V`	`put(K key, V value)`
`private void`	`putResize(K key, V value)` Skips checks for existing keys.
`private void`	`putStash(K key, V value)`
`V`	`remove(K key)`
`(package private) V`	`removeStash(K key)`
`(package private) void`	`removeStashIndex(int index)`
`private void`	`resize(int newSize)`
`void`	`shrink(int maximumCapacity)` Reduces the size of the backing arrays to be the specified capacity or less.
`java.lang.String`	`toString()`
`IdentityMap.Values<V>`	`values()` Returns an iterator for the values in the map.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - PRIME1
```
private static final int PRIME1
```
    See Also:
    
    Constant Field Values
  - PRIME2
```
private static final int PRIME2
```
    See Also:
    
    Constant Field Values
  - PRIME3
```
private static final int PRIME3
```
    See Also:
    
    Constant Field Values
  - size
```
public int size
```
  - keyTable
```
K[] keyTable
```
  - valueTable
```
V[] valueTable
```
  - capacity
```
int capacity
```
  - stashSize
```
int stashSize
```
  - loadFactor
```
private float loadFactor
```
  - hashShift
```
private int hashShift
```
  - mask
```
private int mask
```
  - threshold
```
private int threshold
```
  - stashCapacity
```
private int stashCapacity
```
  - pushIterations
```
private int pushIterations
```
  - entries
```
private IdentityMap.Entries entries
```
  - values
```
private IdentityMap.Values values
```
  - keys
```
private IdentityMap.Keys keys
```
- Constructor Detail
  - IdentityMap
```
public IdentityMap()
```
    Creates a new map with an initial capacity of 32 and a load factor of 0.8. This map will hold 25 items before growing the backing table.
  - IdentityMap
```
public IdentityMap(int initialCapacity)
```
    Creates a new map with a load factor of 0.8. This map will hold initialCapacity * 0.8 items before growing the backing table.
  - IdentityMap
```
public IdentityMap(int initialCapacity,
                   float loadFactor)
```
    Creates a new map with the specified initial capacity and load factor. This map will hold initialCapacity * loadFactor items before growing the backing table.
- Method Detail
  - put
```
public V put(K key,
             V value)
```
  - putResize
```
private void putResize(K key,
                       V value)
```
    Skips checks for existing keys.
  - push
```
private void push(K insertKey,
                  V insertValue,
                  int index1,
                  K key1,
                  int index2,
                  K key2,
                  int index3,
                  K key3)
```
  - putStash
```
private void putStash(K key,
                      V value)
```
  - get
```
public V get(K key)
```
  - get
```
public V get(K key,
             V defaultValue)
```
  - getStash
```
private V getStash(K key,
                   V defaultValue)
```
  - remove
```
public V remove(K key)
```
  - removeStash
```
V removeStash(K key)
```
  - removeStashIndex
```
void removeStashIndex(int index)
```
  - shrink
```
public void shrink(int maximumCapacity)
```
    Reduces the size of the backing arrays to be the specified capacity or less. If the capacity is already less, nothing is done. If the map contains more items than the specified capacity, nothing is done.
  - clear
```
public void clear(int maximumCapacity)
```
    Clears the map and reduces the size of the backing arrays to be the specified capacity if they are larger.
  - clear
```
public void clear()
```
  - containsValue
```
public boolean containsValue(java.lang.Object value,
                             boolean identity)
```
    Returns true if the specified value is in the map. Note this traverses the entire map and compares every value, which may be an expensive operation.
    
    Parameters:
    
    identity - If true, uses == to compare the specified value with values in the map. If false, uses Object.equals(Object).
  - containsKey
```
public boolean containsKey(K key)
```
  - containsKeyStash
```
private boolean containsKeyStash(K key)
```
  - findKey
```
public K findKey(java.lang.Object value,
                 boolean identity)
```
    Returns the key for the specified value, or null if it is not in the map. Note this traverses the entire map and compares every value, which may be an expensive operation.
    
    Parameters:
    
    identity - If true, uses == to compare the specified value with values in the map. If false, uses Object.equals(Object).
  - ensureCapacity
```
public void ensureCapacity(int additionalCapacity)
```
    Increases the size of the backing array to acommodate the specified number of additional items. Useful before adding many items to avoid multiple backing array resizes.
  - resize
```
private void resize(int newSize)
```
  - hash2
```
private int hash2(int h)
```
  - hash3
```
private int hash3(int h)
```
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object
  - entries
```
public IdentityMap.Entries<K,V> entries()
```
    Returns an iterator for the entries in the map. Remove is supported. Note that the same iterator instance is returned each time this method is called. Use the IdentityMap.Entries constructor for nested or multithreaded iteration.
  - values
```
public IdentityMap.Values<V> values()
```
    Returns an iterator for the values in the map. Remove is supported. Note that the same iterator instance is returned each time this method is called. Use the IdentityMap.Entries constructor for nested or multithreaded iteration.
  - keys
```
public IdentityMap.Keys<K> keys()
```
    Returns an iterator for the keys in the map. Remove is supported. Note that the same iterator instance is returned each time this method is called. Use the IdentityMap.Entries constructor for nested or multithreaded iteration.

Class IdentityMap<K,V>

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

PRIME1

PRIME2

PRIME3

size

keyTable

valueTable

capacity

stashSize

loadFactor

hashShift

mask

threshold

stashCapacity

pushIterations

entries

values

keys

Constructor Detail

IdentityMap

IdentityMap

IdentityMap

Method Detail

put

putResize

push

putStash

get

get

getStash

remove

removeStash

removeStashIndex

shrink

clear

clear

containsValue

containsKey

containsKeyStash

findKey

ensureCapacity

resize

hash2

hash3

toString

entries

values

keys