Package com.esotericsoftware.kryo.util
Class IdentityMap<K,V>
java.lang.Object
com.esotericsoftware.kryo.util.IdentityMap<K,V>
An unordered map that uses identity comparison for keys. This implementation is a cuckoo hash map using 3 hashes (if table
size is less than 2^16) or 4 hashes (if table size is greater than or equal to 2^16), 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.
4
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.
4
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.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic class
static class
static class
private static class
static class
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate boolean
(package private) int
private IdentityMap.Entries
private int
private IdentityMap.Keys
(package private) K[]
private float
private int
private static final int
private static final int
private static final int
private int
int
private int
(package private) int
private int
private IdentityMap.Values
(package private) V[]
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Constructor Summary
ConstructorsConstructorDescriptionCreates 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
Modifier and TypeMethodDescriptionvoid
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
(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.entries()
Returns an iterator for the entries in the map.Returns the key for the specified value, or null if it is not in the map.private V
private int
hash2
(int h) private int
hash3
(int h) private int
hash4
(int h) 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, int index4, K key4) private void
Skips checks for existing keys.private void
(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.toString()
values()
Returns an iterator for the values in the map.
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Field Details
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PRIME2
private static final int PRIME2- See Also:
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PRIME3
private static final int PRIME3- See Also:
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PRIME4
private static final int PRIME4- See Also:
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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 -
bigTable
private boolean bigTable -
entries
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values
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keys
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Constructor Details
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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.
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Method Details
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put
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putResize
Skips checks for existing keys. -
push
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putStash
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get
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get
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getStash
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remove
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removeStash
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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
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, usesObject.equals(Object)
.
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containsKey
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containsKeyStash
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findKey
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, usesObject.equals(Object)
.
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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) -
hash4
private int hash4(int h) -
toString
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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 theIdentityMap.Entries
constructor for nested or multithreaded iteration. -
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 theIdentityMap.Entries
constructor for nested or multithreaded iteration. -
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 theIdentityMap.Entries
constructor for nested or multithreaded iteration.
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