Package it.unimi.dsi.fastutil.chars

Class Char2ObjectOpenHashMap<V>

  • All Implemented Interfaces:
    Char2ObjectFunction<V>, Char2ObjectMap<V>, Function<Character,​V>, Hash, Serializable, Cloneable, Function<Character,​V>, IntFunction<V>, Map<Character,​V>
    public class Char2ObjectOpenHashMap<V>
extends AbstractChar2ObjectMap<V>
implements Serializable, Cloneable, Hash
    A type-specific hash map 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.

    See Also:
    Hash, HashCommon, Serialized Form

    • Constructor Detail

      • Char2ObjectOpenHashMap

        public Char2ObjectOpenHashMap​(int expected,
                              float f)
        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.

      • Char2ObjectOpenHashMap

        public Char2ObjectOpenHashMap​(int expected)
        Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor.
        Parameters:
        expected - the expected number of elements in the hash map.

      • Char2ObjectOpenHashMap

        public Char2ObjectOpenHashMap​(Map<? extends Character,​? extends V> m,
                              float f)
        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.

      • Char2ObjectOpenHashMap

        public Char2ObjectOpenHashMap​(Map<? extends Character,​? extends V> m)
        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.

      • Char2ObjectOpenHashMap

        public Char2ObjectOpenHashMap​(Char2ObjectMap<V> m,
                              float f)
        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.

      • Char2ObjectOpenHashMap

        public Char2ObjectOpenHashMap​(Char2ObjectMap<V> m)
        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.

      • Char2ObjectOpenHashMap

        public Char2ObjectOpenHashMap​(char[] k,
                              V[] v,
                              float f)
        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.
        Throws:
        IllegalArgumentException - if k and v have different lengths.

      • Char2ObjectOpenHashMap

        public Char2ObjectOpenHashMap​(char[] k,
                              V[] v)
        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.
        Throws:
        IllegalArgumentException - if k and v have different lengths.

    • Method Detail

      • getOrDefault

        public V getOrDefault​(char 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 Char2ObjectMap<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:
        Map.getOrDefault(Object, Object)

      • putIfAbsent

        public V putIfAbsent​(char 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 Char2ObjectMap<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:
        Map.putIfAbsent(Object, Object)

      • remove

        public boolean remove​(char 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 Char2ObjectMap<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:
        Map.remove(Object, Object)

      • replace

        public boolean replace​(char 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 Char2ObjectMap<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:
        Map.replace(Object, Object, Object)

      • replace

        public V replace​(char k,
                 V v)
        Replaces the entry for the specified key only if it is currently mapped to some value.
        Specified by:
        replace in interface Char2ObjectMap<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:
        Map.replace(Object, Object)

      • computeIfAbsent

        public V computeIfAbsent​(char k,
                         IntFunction<? 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.

        Note that contrarily to the default computeIfAbsent(), it is not possible to not add a value for a given key, since the mappingFunction cannot return null. If such a behavior is needed, please use the corresponding nullable version.

        Specified by:
        computeIfAbsent in interface Char2ObjectMap<V>
        Parameters:
        k - 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:
        Map.computeIfAbsent(Object, java.util.function.Function)

      • compute

        public V compute​(char k,
                 BiFunction<? super Character,​? 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 Char2ObjectMap<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:
        Map.compute(Object, java.util.function.BiFunction)

      • merge

        public V merge​(char k,
               V v,
               BiFunction<? super V,​? super V,​? extends V> remappingFunction)
        If the specified key is not already associated with a value or is associated with null, associates it with the given non-null 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 Char2ObjectMap<V>
        Parameters:
        k - key with which the resulting value is to be associated.
        v - the non-null 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:
        Map.merge(Object, Object, java.util.function.BiFunction)

      • char2ObjectEntrySet

        public Char2ObjectMap.FastEntrySet<V> char2ObjectEntrySet()
        Description copied from interface: Char2ObjectMap
        Returns a type-specific set view of the mappings contained in this map.

        This method is necessary because there is no inheritance along type parameters: it is thus impossible to strengthen Map.entrySet() so that it returns an ObjectSet of type-specific entries (the latter makes it possible to access keys and values with type-specific methods).

        Specified by:
        char2ObjectEntrySet in interface Char2ObjectMap<V>
        Returns:
        a type-specific set view of the mappings contained in this map.
        See Also:
        Map.entrySet()

      • keySet

        public CharSet keySet()
        Description copied from class: AbstractChar2ObjectMap
        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.

        Specified by:
        keySet in interface Char2ObjectMap<V>
        Specified by:
        keySet in interface Map<Character,​V>
        Overrides:
        keySet in class AbstractChar2ObjectMap<V>
        Returns:
        a set view of the keys of this map; it may be safely cast to a type-specific interface.
        See Also:
        Map.keySet()

      • values

        public ObjectCollection<V> values()
        Description copied from class: AbstractChar2ObjectMap
        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.

        Specified by:
        values in interface Char2ObjectMap<V>
        Specified by:
        values in interface Map<Character,​V>
        Overrides:
        values in class AbstractChar2ObjectMap<V>
        Returns:
        a set view of the values of this map; it may be safely cast to a type-specific interface.
        See Also:
        Map.values()

      • 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(int)

      • 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:
        trim()

      • clone

        public Char2ObjectOpenHashMap<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<Character,​V>
        Overrides:
        hashCode in class AbstractChar2ObjectMap<V>
        Returns:
        a hash code for this map.