Class ObjectMap<K,V>

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

public class ObjectMap<K,V> extends 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.
  • Field Details

    • PRIME2

      private static final int PRIME2
      See Also:
    • PRIME3

      private static final int PRIME3
      See Also:
    • PRIME4

      private static final int PRIME4
      See Also:
    • random

      static Random random
    • 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
  • Constructor Details

    • 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.
    • 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.
    • 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.
    • ObjectMap

      public ObjectMap(ObjectMap<? extends K,? extends V> map)
      Creates a new map identical to the specified map.
  • Method Details

    • put

      public V put(K key, V value)
      Returns the old value associated with the specified key, or null.
    • put_internal

      private V put_internal(K key, V value)
    • putAll

      public void putAll(ObjectMap<K,V> map)
    • 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, int index4, K key4)
    • putStash

      private void putStash(K key, V value)
    • get

      public V get(K key)
    • getStash

      private V getStash(K key)
    • 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.
    • 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, the next highest power of two capacity is used instead.
    • 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(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(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)
    • hash4

      private int hash4(int h)
    • toString

      public String toString()
      Overrides:
      toString in class Object
    • entries

      public ObjectMap.Entries<K,V> entries()
      Returns an iterator for the entries in the map. Remove is supported.
    • values

      public ObjectMap.Values<V> values()
      Returns an iterator for the values in the map. Remove is supported.
    • keys

      public ObjectMap.Keys<K> keys()
      Returns an iterator for the keys in the map. Remove is supported.
    • nextPowerOfTwo

      public static int nextPowerOfTwo(int value)