Package com.esotericsoftware.kryo.util

Class CuckooObjectMap<K,​V>

  • 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

    • Field Summary

      Fields 
      Modifier and Type Field Description
      int size  

    • 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.

    • 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.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

    • Field Detail

      • size

        public int size

    • Constructor Detail

      • 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.

      • 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.

      • 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.

      • CuckooObjectMap

        public CuckooObjectMap​(CuckooObjectMap<? extends K,​? extends V> map)
        Creates a new map identical to the specified map.

    • Method Detail

      • put

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

      • get

        public V get​(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.

      • remove

        public V remove​(K key)

      • 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​(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)

      • 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.

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object

      • entries

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

      • values

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

      • keys

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

      • nextPowerOfTwo

        public static int nextPowerOfTwo​(int value)