Package com.esotericsoftware.kryo.util
Class ObjectMap<K,V>
- java.lang.Object
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- com.esotericsoftware.kryo.util.ObjectMap<K,V>
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public class ObjectMap<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.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
ObjectMap.Entries<K,V>
static class
ObjectMap.Entry<K,V>
static class
ObjectMap.Keys<K>
private static class
ObjectMap.MapIterator<K,V>
static class
ObjectMap.Values<V>
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Field Summary
Fields Modifier and Type Field Description private boolean
bigTable
(package private) int
capacity
private int
hashShift
(package private) K[]
keyTable
private float
loadFactor
private int
mask
private static int
PRIME2
private static int
PRIME3
private static int
PRIME4
private int
pushIterations
(package private) static java.util.Random
random
int
size
private int
stashCapacity
(package private) int
stashSize
private int
threshold
(package private) V[]
valueTable
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Constructor Summary
Constructors Constructor Description ObjectMap()
Creates a new map with an initial capacity of 32 and a load factor of 0.8.ObjectMap(int initialCapacity)
Creates a new map with a load factor of 0.8.ObjectMap(int initialCapacity, float loadFactor)
Creates a new map with the specified initial capacity and load factor.ObjectMap(ObjectMap<? 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)
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.ObjectMap.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.private V
getStash(K key)
private V
getStash(K key, V defaultValue)
private int
hash2(int h)
private int
hash3(int h)
private int
hash4(int h)
ObjectMap.Keys<K>
keys()
Returns an iterator for the keys in the map.static int
nextPowerOfTwo(int value)
private void
push(K insertKey, V insertValue, int index1, K key1, int index2, K key2, int index3, K key3, int index4, K key4)
V
put(K key, V value)
Returns the old value associated with the specified key, or null.private V
put_internal(K key, V value)
void
putAll(ObjectMap<K,V> map)
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()
ObjectMap.Values<V>
values()
Returns an iterator for the values in the map.
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Field Detail
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PRIME2
private static final int PRIME2
- See Also:
- Constant Field Values
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PRIME3
private static final int PRIME3
- See Also:
- Constant Field Values
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PRIME4
private static final int PRIME4
- See Also:
- Constant Field Values
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random
static java.util.Random random
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size
public int size
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keyTable
K[] keyTable
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valueTable
V[] valueTable
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capacity
int capacity
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stashSize
int stashSize
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loadFactor
private float loadFactor
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hashShift
private int hashShift
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mask
private int mask
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threshold
private int threshold
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stashCapacity
private int stashCapacity
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pushIterations
private int pushIterations
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bigTable
private boolean bigTable
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Constructor Detail
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ObjectMap
public ObjectMap()
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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ObjectMap
public ObjectMap(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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ObjectMap
public ObjectMap(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 Detail
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push
private void push(K insertKey, V insertValue, int index1, K key1, int index2, K key2, int index3, K key3, int index4, K key4)
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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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removeStashIndex
void removeStashIndex(int index)
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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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containsKeyStash
private boolean containsKeyStash(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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resize
private void resize(int newSize)
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hash2
private int hash2(int h)
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hash3
private int hash3(int h)
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hash4
private int hash4(int h)
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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entries
public ObjectMap.Entries<K,V> entries()
Returns an iterator for the entries in the map. Remove is supported.
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values
public ObjectMap.Values<V> values()
Returns an iterator for the values in the map. Remove is supported.
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keys
public ObjectMap.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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