Package com.esotericsoftware.kryo.util
Class CuckooObjectMap<K,V>
- java.lang.Object
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- com.esotericsoftware.kryo.util.CuckooObjectMap<K,V>
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public class CuckooObjectMap<K,V> extends java.lang.Object
An unordered map. 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.
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.- Author:
- Nathan Sweet
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
CuckooObjectMap.Entries<K,V>
static class
CuckooObjectMap.Entry<K,V>
static class
CuckooObjectMap.Keys<K>
static class
CuckooObjectMap.Values<V>
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Field Summary
Fields Modifier and Type Field Description int
size
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Constructor Summary
Constructors Constructor Description CuckooObjectMap()
Creates a new map with an initial capacity of 32 and a load factor of 0.8.CuckooObjectMap(int initialCapacity)
Creates a new map with a load factor of 0.8.CuckooObjectMap(int initialCapacity, float loadFactor)
Creates a new map with the specified initial capacity and load factor.CuckooObjectMap(CuckooObjectMap<? extends K,? extends V> map)
Creates a new map identical to the specified map.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method 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)
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.CuckooObjectMap.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)
Returns the value for the specified key, or the default value if the key is not in the map.CuckooObjectMap.Keys<K>
keys()
Returns an iterator for the keys in the map.static int
nextPowerOfTwo(int value)
V
put(K key, V value)
Returns the old value associated with the specified key, or null.void
putAll(CuckooObjectMap<K,V> map)
V
remove(K key)
void
shrink(int maximumCapacity)
Reduces the size of the backing arrays to be the specified capacity or less.java.lang.String
toString()
CuckooObjectMap.Values<V>
values()
Returns an iterator for the values in the map.
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Constructor Detail
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CuckooObjectMap
public CuckooObjectMap()
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.
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CuckooObjectMap
public CuckooObjectMap(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.
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CuckooObjectMap
public CuckooObjectMap(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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CuckooObjectMap
public CuckooObjectMap(CuckooObjectMap<? extends K,? extends V> map)
Creates a new map identical to the specified map.
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Method Detail
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putAll
public void putAll(CuckooObjectMap<K,V> map)
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get
public V get(K key, V defaultValue)
Returns the value for the specified key, or the default value if the key is not in the map.
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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, the next highest power of two capacity is used instead.
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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.
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clear
public void clear()
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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, usesObject.equals(Object)
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containsKey
public boolean containsKey(K key)
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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, 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.
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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entries
public CuckooObjectMap.Entries<K,V> entries()
Returns an iterator for the entries in the map. Remove is supported.
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values
public CuckooObjectMap.Values<V> values()
Returns an iterator for the values in the map. Remove is supported.
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keys
public CuckooObjectMap.Keys<K> keys()
Returns an iterator for the keys in the map. Remove is supported.
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nextPowerOfTwo
public static int nextPowerOfTwo(int value)
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