Class IdentityObjectIntMap<K>


  • public class IdentityObjectIntMap<K>
    extends Object
    An unordered map where identity comparison is used for keys and the values are ints. 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. 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
      IdentityObjectIntMap()
      Creates a new map with an initial capacity of 32 and a load factor of 0.8.
      IdentityObjectIntMap​(int initialCapacity)
      Creates a new map with a load factor of 0.8.
      IdentityObjectIntMap​(int initialCapacity, float loadFactor)
      Creates a new map with the specified initial capacity and load factor.
    • Method Summary

      All 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​(int value)
      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.
      K findKey​(int value)
      Returns the key for the specified value, or null if it is not in the map.
      int get​(K key, int defaultValue)  
      int getAndIncrement​(K key, int defaultValue, int increment)
      Returns the key's current value and increments the stored value.
      void put​(K key, int value)  
      int remove​(K key, int defaultValue)  
      void shrink​(int maximumCapacity)
      Reduces the size of the backing arrays to be the specified capacity or less.
      String toString()  
    • Field Detail

      • size

        public int size
    • Constructor Detail

      • IdentityObjectIntMap

        public IdentityObjectIntMap()
        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.
      • IdentityObjectIntMap

        public IdentityObjectIntMap​(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.
      • IdentityObjectIntMap

        public IdentityObjectIntMap​(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.
    • Method Detail

      • put

        public void put​(K key,
                        int value)
      • get

        public int get​(K key,
                       int defaultValue)
        Parameters:
        defaultValue - Returned if the key was not associated with a value.
      • getAndIncrement

        public int getAndIncrement​(K key,
                                   int defaultValue,
                                   int increment)
        Returns the key's current value and increments the stored value. If the key is not in the map, defaultValue + increment is put into the map.
      • remove

        public int remove​(K key,
                          int defaultValue)
      • 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

        public boolean containsValue​(int value)
        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.
      • containsKey

        public boolean containsKey​(K key)
      • findKey

        public K findKey​(int value)
        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.
      • 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.