Package com.esotericsoftware.kryo.util

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.
Author:
Nathan Sweet

  • 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>
     
    static class 
    ObjectMap.Values<V>
     

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    int
    size
     

  • 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.

  • Method Summary

    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(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(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.
    ObjectMap.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(ObjectMap<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.
    String
    toString()
     
    ObjectMap.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 Details

    • size

      public int size

  • 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.

    • putAll

      public void putAll(ObjectMap<K,V> map)

    • 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(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(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 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)