Package it.unimi.dsi.fastutil.objects

Class Object2ReferenceLinkedOpenCustomHashMap<K,V>

java.lang.Object
it.unimi.dsi.fastutil.objects.AbstractObject2ReferenceFunction<K,V>
it.unimi.dsi.fastutil.objects.AbstractObject2ReferenceMap<K,V>
it.unimi.dsi.fastutil.objects.AbstractObject2ReferenceSortedMap<K,V>
it.unimi.dsi.fastutil.objects.Object2ReferenceLinkedOpenCustomHashMap<K,V>
All Implemented Interfaces:
Function<K,V>, Hash, Object2ReferenceFunction<K,V>, Object2ReferenceMap<K,V>, Object2ReferenceSortedMap<K,V>, Serializable, Cloneable, Function<K,V>, Map<K,V>, SequencedMap<K,V>, SortedMap<K,V>
public class Object2ReferenceLinkedOpenCustomHashMap<K,V> extends AbstractObject2ReferenceSortedMap<K,V> implements Serializable, Cloneable, Hash
A type-specific linked hash map with with a fast, small-footprint implementation.

Instances of this class use a hash table to represent a map. The table is filled up to a specified load factor, and then doubled in size to accommodate new entries. If the table is emptied below one fourth of the load factor, it is halved in size; however, the table is never reduced to a size smaller than that at creation time: this approach makes it possible to create maps with a large capacity in which insertions and deletions do not cause immediately rehashing. Moreover, halving is not performed when deleting entries from an iterator, as it would interfere with the iteration process.

Note that clear() does not modify the hash table size. Rather, a family of trimming methods lets you control the size of the table; this is particularly useful if you reuse instances of this class.

Entries returned by the type-specific Object2ReferenceMap.entrySet() method implement the suitable type-specific Pair interface; only values are mutable.

Iterators generated by this map will enumerate pairs in the same order in which they have been added to the map (addition of pairs whose key is already present in the map does not change the iteration order). Note that this order has nothing in common with the natural order of the keys. The order is kept by means of a doubly linked list, represented via an array of longs parallel to the table.

This class implements the interface of a sorted map, so to allow easy access of the iteration order: for instance, you can get the first key in iteration order with firstKey() without having to create an iterator; however, this class partially violates the SortedMap contract because all submap methods throw an exception and comparator() returns always null.

Additional methods, such as getAndMoveToFirst(), make it easy to use instances of this class as a cache (e.g., with LRU policy).

The iterators provided by the views of this class using are type-specific list iterators, and can be started at any element which is a key of the map, or a NoSuchElementException exception will be thrown. If, however, the provided element is not the first or last key in the map, the first access to the list index will require linear time, as in the worst case the entire key set must be scanned in iteration order to retrieve the positional index of the starting key. If you use just the methods of a type-specific BidirectionalIterator, however, all operations will be performed in constant time.

See Also:

  • Constructor Details

    • Object2ReferenceLinkedOpenCustomHashMap

      public Object2ReferenceLinkedOpenCustomHashMap(int expected, float f, Hash.Strategy<? super K> strategy)
      Creates a new hash map.

      The actual table size will be the least power of two greater than expected/f.

      Parameters:
      expected - the expected number of elements in the hash map.
      f - the load factor.
      strategy - the strategy.

    • Object2ReferenceLinkedOpenCustomHashMap

      public Object2ReferenceLinkedOpenCustomHashMap(int expected, Hash.Strategy<? super K> strategy)
      Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor.
      Parameters:
      expected - the expected number of elements in the hash map.
      strategy - the strategy.

    • Object2ReferenceLinkedOpenCustomHashMap

      public Object2ReferenceLinkedOpenCustomHashMap(Hash.Strategy<? super K> strategy)
      Creates a new hash map with initial expected Hash.DEFAULT_INITIAL_SIZE entries and Hash.DEFAULT_LOAD_FACTOR as load factor.
      Parameters:
      strategy - the strategy.

    • Object2ReferenceLinkedOpenCustomHashMap

      public Object2ReferenceLinkedOpenCustomHashMap(Map<? extends K,? extends V> m, float f, Hash.Strategy<? super K> strategy)
      Creates a new hash map copying a given one.
      Parameters:
      m - a Map to be copied into the new hash map.
      f - the load factor.
      strategy - the strategy.

    • Object2ReferenceLinkedOpenCustomHashMap

      public Object2ReferenceLinkedOpenCustomHashMap(Map<? extends K,? extends V> m, Hash.Strategy<? super K> strategy)
      Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given one.
      Parameters:
      m - a Map to be copied into the new hash map.
      strategy - the strategy.

    • Object2ReferenceLinkedOpenCustomHashMap

      public Object2ReferenceLinkedOpenCustomHashMap(Object2ReferenceMap<K,V> m, float f, Hash.Strategy<? super K> strategy)
      Creates a new hash map copying a given type-specific one.
      Parameters:
      m - a type-specific map to be copied into the new hash map.
      f - the load factor.
      strategy - the strategy.

    • Object2ReferenceLinkedOpenCustomHashMap

      public Object2ReferenceLinkedOpenCustomHashMap(Object2ReferenceMap<K,V> m, Hash.Strategy<? super K> strategy)
      Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific one.
      Parameters:
      m - a type-specific map to be copied into the new hash map.
      strategy - the strategy.

    • Object2ReferenceLinkedOpenCustomHashMap

      public Object2ReferenceLinkedOpenCustomHashMap(K[] k, V[] v, float f, Hash.Strategy<? super K> strategy)
      Creates a new hash map using the elements of two parallel arrays.
      Parameters:
      k - the array of keys of the new hash map.
      v - the array of corresponding values in the new hash map.
      f - the load factor.
      strategy - the strategy.
      Throws:
      IllegalArgumentException - if k and v have different lengths.

    • Object2ReferenceLinkedOpenCustomHashMap

      public Object2ReferenceLinkedOpenCustomHashMap(K[] k, V[] v, Hash.Strategy<? super K> strategy)
      Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor using the elements of two parallel arrays.
      Parameters:
      k - the array of keys of the new hash map.
      v - the array of corresponding values in the new hash map.
      strategy - the strategy.
      Throws:
      IllegalArgumentException - if k and v have different lengths.

  • Method Details

    • strategy

      public Hash.Strategy<? super K> strategy()
      Returns the hashing strategy.
      Returns:
      the hashing strategy of this custom hash map.

    • ensureCapacity

      public void ensureCapacity(int capacity)
      Ensures that this map can hold a certain number of keys without rehashing.
      Parameters:
      capacity - a number of keys; there will be no rehashing unless the map size exceeds this number.

    • putAll

      public void putAll(Map<? extends K,? extends V> m)
      Description copied from class: AbstractObject2ReferenceMap
      Specified by:
      putAll in interface Map<K,V>
      Overrides:
      putAll in class AbstractObject2ReferenceMap<K,V>

    • put

      public V put(K k, V v)
      Description copied from interface: Object2ReferenceMap
      Adds a pair to the map (optional operation).

      This default implementation just delegates to the corresponding function method.

      Specified by:
      put in interface Function<K,V>
      Specified by:
      put in interface Map<K,V>
      Specified by:
      put in interface Object2ReferenceFunction<K,V>
      Specified by:
      put in interface Object2ReferenceMap<K,V>
      Parameters:
      k - the key.
      v - the value.
      Returns:
      the old value, or the default return value if no value was present for the given key.
      See Also:

    • remove

      public V remove(Object k)
      Description copied from interface: Object2ReferenceMap
      Removes the mapping with the given key (optional operation).

      This default implementation just delegates to the corresponding type-specific–function method.

      Specified by:
      remove in interface Function<K,V>
      Specified by:
      remove in interface Map<K,V>
      Specified by:
      remove in interface Object2ReferenceFunction<K,V>
      Specified by:
      remove in interface Object2ReferenceMap<K,V>
      Parameters:
      k - the key.
      Returns:
      the old value, or the default return value if no value was present for the given key.
      See Also:

    • removeFirst

      public V removeFirst()
      Removes the mapping associated with the first key in iteration order.
      Returns:
      the value previously associated with the first key in iteration order.
      Throws:
      NoSuchElementException - is this map is empty.

    • removeLast

      public V removeLast()
      Removes the mapping associated with the last key in iteration order.
      Returns:
      the value previously associated with the last key in iteration order.
      Throws:
      NoSuchElementException - is this map is empty.

    • getAndMoveToFirst

      public V getAndMoveToFirst(K k)
      Returns the value to which the given key is mapped; if the key is present, it is moved to the first position of the iteration order.
      Parameters:
      k - the key.
      Returns:
      the corresponding value, or the default return value if no value was present for the given key.

    • getAndMoveToLast

      public V getAndMoveToLast(K k)
      Returns the value to which the given key is mapped; if the key is present, it is moved to the last position of the iteration order.
      Parameters:
      k - the key.
      Returns:
      the corresponding value, or the default return value if no value was present for the given key.

    • putAndMoveToFirst

      public V putAndMoveToFirst(K k, V v)
      Adds a pair to the map; if the key is already present, it is moved to the first position of the iteration order.
      Parameters:
      k - the key.
      v - the value.
      Returns:
      the old value, or the default return value if no value was present for the given key.

    • putAndMoveToLast

      public V putAndMoveToLast(K k, V v)
      Adds a pair to the map; if the key is already present, it is moved to the last position of the iteration order.
      Parameters:
      k - the key.
      v - the value.
      Returns:
      the old value, or the default return value if no value was present for the given key.

    • get

      public V get(Object k)
      Description copied from interface: Object2ReferenceFunction
      Returns the value to which the given key is mapped.
      Specified by:
      get in interface Function<K,V>
      Specified by:
      get in interface Map<K,V>
      Specified by:
      get in interface Object2ReferenceFunction<K,V>
      Parameters:
      k - the key.
      Returns:
      the corresponding value, or the default return value if no value was present for the given key.
      See Also:

    • containsKey

      public boolean containsKey(Object k)
      Description copied from class: AbstractObject2ReferenceMap
      Returns true if this function contains a mapping for the specified key.
      Specified by:
      containsKey in interface Function<K,V>
      Specified by:
      containsKey in interface Map<K,V>
      Specified by:
      containsKey in interface Object2ReferenceMap<K,V>
      Overrides:
      containsKey in class AbstractObject2ReferenceMap<K,V>
      Parameters:
      k - the key.
      Returns:
      true if this function associates a value to key.
      See Also:

    • containsValue

      public boolean containsValue(Object v)
      Description copied from class: AbstractObject2ReferenceMap
      Specified by:
      containsValue in interface Map<K,V>
      Overrides:
      containsValue in class AbstractObject2ReferenceMap<K,V>

    • getOrDefault

      public V getOrDefault(Object k, V defaultValue)
      Returns the value to which the specified key is mapped, or the defaultValue if this map contains no mapping for the key.
      Specified by:
      getOrDefault in interface Function<K,V>
      Specified by:
      getOrDefault in interface Map<K,V>
      Specified by:
      getOrDefault in interface Object2ReferenceFunction<K,V>
      Specified by:
      getOrDefault in interface Object2ReferenceMap<K,V>
      Parameters:
      k - the key.
      defaultValue - the default mapping of the key.
      Returns:
      the value to which the specified key is mapped, or the defaultValue if this map contains no mapping for the key.
      See Also:

    • putIfAbsent

      public V putIfAbsent(K k, V v)
      If the specified key is not already associated with a value, associates it with the given value and returns the default return value, else returns the current value.
      Specified by:
      putIfAbsent in interface Map<K,V>
      Specified by:
      putIfAbsent in interface Object2ReferenceMap<K,V>
      Parameters:
      k - key with which the specified value is to be associated.
      v - value to be associated with the specified key.
      Returns:
      the previous value associated with the specified key, or the default return value if there was no mapping for the key.
      See Also:

    • remove

      public boolean remove(Object k, Object v)
      Removes the entry for the specified key only if it is currently mapped to the specified value.
      Specified by:
      remove in interface Map<K,V>
      Specified by:
      remove in interface Object2ReferenceMap<K,V>
      Parameters:
      k - key with which the specified value is associated.
      v - value expected to be associated with the specified key.
      Returns:
      true if the value was removed.
      See Also:

    • replace

      public boolean replace(K k, V oldValue, V v)
      Replaces the entry for the specified key only if currently mapped to the specified value.
      Specified by:
      replace in interface Map<K,V>
      Specified by:
      replace in interface Object2ReferenceMap<K,V>
      Parameters:
      k - key with which the specified value is associated.
      oldValue - value expected to be associated with the specified key.
      v - value to be associated with the specified key.
      Returns:
      true if the value was replaced.
      See Also:

    • replace

      public V replace(K k, V v)
      Replaces the entry for the specified key only if it is currently mapped to some value.
      Specified by:
      replace in interface Map<K,V>
      Specified by:
      replace in interface Object2ReferenceMap<K,V>
      Parameters:
      k - key with which the specified value is associated.
      v - value to be associated with the specified key.
      Returns:
      the previous value associated with the specified key, or the default return value if there was no mapping for the key.
      See Also:

    • computeIfAbsent

      public V computeIfAbsent(K key, Object2ReferenceFunction<? super K,? extends V> mappingFunction)
      If the specified key is not already associated with a value, attempts to compute its value using the given mapping function and enters it into this map, unless the key is not present in the given mapping function.

      This version of computeIfAbsent() uses a type-specific version of fastutil's Function. Since Function has a containsKey() method, it is possible to avoid adding a key by having containsKey() return false for that key.

      Specified by:
      computeIfAbsent in interface Object2ReferenceMap<K,V>
      Parameters:
      key - key with which the specified value is to be associated.
      mappingFunction - the function to compute a value.
      Returns:
      the current (existing or computed) value associated with the specified key.
      See Also:

    • computeIfPresent

      public V computeIfPresent(K k, BiFunction<? super K,? super V,? extends V> remappingFunction)
      If the value for the specified key is present, attempts to compute a new mapping given the key and its current mapped value.
      Specified by:
      computeIfPresent in interface Map<K,V>
      Specified by:
      computeIfPresent in interface Object2ReferenceMap<K,V>
      Parameters:
      k - key with which the specified value is to be associated.
      remappingFunction - the function to compute a value.
      Returns:
      the new value associated with the specified key, or the default return value if none.
      See Also:

    • compute

      public V compute(K k, BiFunction<? super K,? super V,? extends V> remappingFunction)
      Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping).

      If the function returns null, the mapping is removed (or remains absent if initially absent). If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.

      Specified by:
      compute in interface Map<K,V>
      Specified by:
      compute in interface Object2ReferenceMap<K,V>
      Parameters:
      k - key with which the specified value is to be associated.
      remappingFunction - the function to compute a value.
      Returns:
      the new value associated with the specified key, or the default return value if none.
      See Also:

    • merge

      public V merge(K k, V v, BiFunction<? super V,? super V,? extends V> remappingFunction)
      If the specified key is not already associated with a value, associates it with the given value. Otherwise, replaces the associated value with the results of the given remapping function, or removes if the result is null.
      Specified by:
      merge in interface Map<K,V>
      Specified by:
      merge in interface Object2ReferenceMap<K,V>
      Parameters:
      k - key with which the resulting value is to be associated.
      v - the value to be merged with the existing value associated with the key or, if no existing value is associated with the key, to be associated with the key.
      remappingFunction - the function to recompute a value if present.
      Returns:
      the new value associated with the specified key, or the default return value if no value is associated with the key.
      See Also:

    • clear

      public void clear()
      Description copied from interface: Object2ReferenceMap
      Removes all of the mappings from this map (optional operation). The map will be empty after this call returns.
      Specified by:
      clear in interface Function<K,V>
      Specified by:
      clear in interface Map<K,V>
      Specified by:
      clear in interface Object2ReferenceMap<K,V>
      See Also:

    • size

      public int size()
      Description copied from interface: Object2ReferenceMap
      Returns the number of key/value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.
      Specified by:
      size in interface Function<K,V>
      Specified by:
      size in interface Map<K,V>
      Specified by:
      size in interface Object2ReferenceMap<K,V>
      Returns:
      the number of key-value mappings in this map.
      See Also:

    • isEmpty

      public boolean isEmpty()
      Specified by:
      isEmpty in interface Map<K,V>
      Overrides:
      isEmpty in class AbstractObject2ReferenceMap<K,V>

    • firstKey

      public K firstKey()
      Returns the first key of this map in iteration order.
      Specified by:
      firstKey in interface SortedMap<K,V>
      Returns:
      the first key in iteration order.

    • lastKey

      public K lastKey()
      Returns the last key of this map in iteration order.
      Specified by:
      lastKey in interface SortedMap<K,V>
      Returns:
      the last key in iteration order.

    • tailMap

      public Object2ReferenceSortedMap<K,V> tailMap(K from)
      Returns a view of the portion of this sorted map whose keys are greater than or equal to fromKey.
      Specified by:
      tailMap in interface Object2ReferenceSortedMap<K,V>
      Specified by:
      tailMap in interface SortedMap<K,V>
      See Also:
      Implementation Specification:
      This implementation just throws an UnsupportedOperationException.

    • headMap

      public Object2ReferenceSortedMap<K,V> headMap(K to)
      Returns a view of the portion of this sorted map whose keys are strictly less than toKey.
      Specified by:
      headMap in interface Object2ReferenceSortedMap<K,V>
      Specified by:
      headMap in interface SortedMap<K,V>
      See Also:
      Implementation Specification:
      This implementation just throws an UnsupportedOperationException.

    • subMap

      public Object2ReferenceSortedMap<K,V> subMap(K from, K to)
      Returns a view of the portion of this sorted map whose keys range from fromKey, inclusive, to toKey, exclusive.
      Specified by:
      subMap in interface Object2ReferenceSortedMap<K,V>
      Specified by:
      subMap in interface SortedMap<K,V>
      See Also:
      Implementation Specification:
      This implementation just throws an UnsupportedOperationException.

    • comparator

      public Comparator<? super K> comparator()
      Returns the comparator associated with this sorted set, or null if it uses its keys' natural ordering.
      Specified by:
      comparator in interface Object2ReferenceSortedMap<K,V>
      Specified by:
      comparator in interface SortedMap<K,V>
      See Also:
      Implementation Specification:
      This implementation just returns null.

    • object2ReferenceEntrySet

      public Object2ReferenceSortedMap.FastSortedEntrySet<K,V> object2ReferenceEntrySet()
      Description copied from interface: Object2ReferenceSortedMap
      Returns a type-specific sorted-set view of the mappings contained in this map.
      Specified by:
      object2ReferenceEntrySet in interface Object2ReferenceMap<K,V>
      Specified by:
      object2ReferenceEntrySet in interface Object2ReferenceSortedMap<K,V>
      Returns:
      a type-specific sorted-set view of the mappings contained in this map.
      See Also:

    • keySet

      public ObjectSortedSet<K> keySet()
      Description copied from class: AbstractObject2ReferenceSortedMap
      Returns a type-specific-set view of the keys of this map.

      The view is backed by the set returned by Map.entrySet(). Note that no attempt is made at caching the result of this method, as this would require adding some attributes that lightweight implementations would not need. Subclasses may easily override this policy by calling this method and caching the result, but implementors are encouraged to write more efficient ad-hoc implementations.

      The view is backed by the sorted set returned by Map.entrySet(). Note that no attempt is made at caching the result of this method, as this would require adding some attributes that lightweight implementations would not need. Subclasses may easily override this policy by calling this method and caching the result, but implementors are encouraged to write more efficient ad-hoc implementations.

      Specified by:
      keySet in interface Map<K,V>
      Specified by:
      keySet in interface Object2ReferenceMap<K,V>
      Specified by:
      keySet in interface Object2ReferenceSortedMap<K,V>
      Specified by:
      keySet in interface SortedMap<K,V>
      Overrides:
      keySet in class AbstractObject2ReferenceSortedMap<K,V>
      Returns:
      a sorted set view of the keys of this map; it may be safely cast to a type-specific interface.
      See Also:

    • values

      public ReferenceCollection<V> values()
      Description copied from class: AbstractObject2ReferenceSortedMap
      Returns a type-specific-set view of the values of this map.

      The view is backed by the set returned by Map.entrySet(). Note that no attempt is made at caching the result of this method, as this would require adding some attributes that lightweight implementations would not need. Subclasses may easily override this policy by calling this method and caching the result, but implementors are encouraged to write more efficient ad-hoc implementations.

      The view is backed by the sorted set returned by Map.entrySet(). Note that no attempt is made at caching the result of this method, as this would require adding some attributes that lightweight implementations would not need. Subclasses may easily override this policy by calling this method and caching the result, but implementors are encouraged to write more efficient ad-hoc implementations.

      Specified by:
      values in interface Map<K,V>
      Specified by:
      values in interface Object2ReferenceMap<K,V>
      Specified by:
      values in interface Object2ReferenceSortedMap<K,V>
      Specified by:
      values in interface SortedMap<K,V>
      Overrides:
      values in class AbstractObject2ReferenceSortedMap<K,V>
      Returns:
      a type-specific collection view of the values contained in this map.
      See Also:

    • trim

      public boolean trim()
      Rehashes the map, making the table as small as possible.

      This method rehashes the table to the smallest size satisfying the load factor. It can be used when the set will not be changed anymore, so to optimize access speed and size.

      If the table size is already the minimum possible, this method does nothing.

      Returns:
      true if there was enough memory to trim the map.
      See Also:

    • trim

      public boolean trim(int n)
      Rehashes this map if the table is too large.

      Let N be the smallest table size that can hold max(n,size()) entries, still satisfying the load factor. If the current table size is smaller than or equal to N, this method does nothing. Otherwise, it rehashes this map in a table of size N.

      This method is useful when reusing maps. Clearing a map leaves the table size untouched. If you are reusing a map many times, you can call this method with a typical size to avoid keeping around a very large table just because of a few large transient maps.

      Parameters:
      n - the threshold for the trimming.
      Returns:
      true if there was enough memory to trim the map.
      See Also:

    • clone

      public Object2ReferenceLinkedOpenCustomHashMap<K,V> clone()
      Returns a deep copy of this map.

      This method performs a deep copy of this hash map; the data stored in the map, however, is not cloned. Note that this makes a difference only for object keys.

      Returns:
      a deep copy of this map.

    • hashCode

      public int hashCode()
      Returns a hash code for this map. This method overrides the generic method provided by the superclass. Since equals() is not overriden, it is important that the value returned by this method is the same value as the one returned by the overriden method.
      Specified by:
      hashCode in interface Map<K,V>
      Overrides:
      hashCode in class AbstractObject2ReferenceMap<K,V>
      Returns:
      a hash code for this map.