Class IdentityHashMap

    • Constructor Detail

      • IdentityHashMap

        public IdentityHashMap​(int initialCapacity,
                               float loadFactor)
        Constructs a new, empty map with the specified initial capacity and the specified load factor.
        Parameters:
        initialCapacity - the initial capacity of the IdentityHashMap.
        loadFactor - the load factor of the IdentityHashMap
        Throws:
        IllegalArgumentException - if the initial capacity is less than zero, or if the load factor is nonpositive.
      • IdentityHashMap

        public IdentityHashMap​(int initialCapacity)
        Constructs a new, empty map with the specified initial capacity and default load factor, which is 0.75.
        Parameters:
        initialCapacity - the initial capacity of the IdentityHashMap.
        Throws:
        IllegalArgumentException - if the initial capacity is less than zero.
      • IdentityHashMap

        public IdentityHashMap()
        Constructs a new, empty map with a default capacity and load factor, which is 0.75.
      • IdentityHashMap

        public IdentityHashMap​(Map t)
        Constructs a new map with the same mappings as the given map. The map is created with a capacity of twice the number of mappings in the given map or 11 (whichever is greater), and a default load factor, which is 0.75.
        Parameters:
        t - the map whose mappings are to be placed in this map.
    • Method Detail

      • size

        public int size()
        Returns the number of key-value mappings in this map.
        Specified by:
        size in interface Map
        Overrides:
        size in class AbstractMap
        Returns:
        the number of key-value mappings in this map.
      • isEmpty

        public boolean isEmpty()
        Returns true if this map contains no key-value mappings.
        Specified by:
        isEmpty in interface Map
        Overrides:
        isEmpty in class AbstractMap
        Returns:
        true if this map contains no key-value mappings.
      • containsValue

        public boolean containsValue​(Object value)
        Returns true if this map maps one or more keys to the specified value.
        Specified by:
        containsValue in interface Map
        Overrides:
        containsValue in class AbstractMap
        Parameters:
        value - value whose presence in this map is to be tested.
        Returns:
        true if this map maps one or more keys to the specified value.
      • containsKey

        public boolean containsKey​(Object key)
        Returns true if this map contains a mapping for the specified key.
        Specified by:
        containsKey in interface Map
        Overrides:
        containsKey in class AbstractMap
        Parameters:
        key - key whose presence in this Map is to be tested.
        Returns:
        true if this map contains a mapping for the specified key.
      • get

        public Object get​(Object key)
        Returns the value to which this map maps the specified key. Returns null if the map contains no mapping for this key. A return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.
        Specified by:
        get in interface Map
        Overrides:
        get in class AbstractMap
        Parameters:
        key - key whose associated value is to be returned.
        Returns:
        the value to which this map maps the specified key.
      • put

        public Object put​(Object key,
                          Object value)
        Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced.
        Specified by:
        put in interface Map
        Overrides:
        put in class AbstractMap
        Parameters:
        key - key with which the specified value is to be associated.
        value - value to be associated with the specified key.
        Returns:
        previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the IdentityHashMap previously associated null with the specified key.
      • remove

        public Object remove​(Object key)
        Removes the mapping for this key from this map if present.
        Specified by:
        remove in interface Map
        Overrides:
        remove in class AbstractMap
        Parameters:
        key - key whose mapping is to be removed from the map.
        Returns:
        previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key.
      • putAll

        public void putAll​(Map t)
        Copies all of the mappings from the specified map to this one. These mappings replace any mappings that this map had for any of the keys currently in the specified Map.
        Specified by:
        putAll in interface Map
        Overrides:
        putAll in class AbstractMap
        Parameters:
        t - Mappings to be stored in this map.
      • clear

        public void clear()
        Removes all mappings from this map.
        Specified by:
        clear in interface Map
        Overrides:
        clear in class AbstractMap
      • clone

        public Object clone()
        Returns a shallow copy of this IdentityHashMap instance: the keys and values themselves are not cloned.
        Overrides:
        clone in class AbstractMap
        Returns:
        a shallow copy of this map.
      • keySet

        public Set keySet()
        Returns a set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice versa. The set supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.
        Specified by:
        keySet in interface Map
        Overrides:
        keySet in class AbstractMap
        Returns:
        a set view of the keys contained in this map.
      • values

        public Collection values()
        Returns a collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice versa. The collection supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.
        Specified by:
        values in interface Map
        Overrides:
        values in class AbstractMap
        Returns:
        a collection view of the values contained in this map.
      • entrySet

        public Set entrySet()
        Returns a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry. The collection is backed by the map, so changes to the map are reflected in the collection, and vice versa. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.
        Specified by:
        entrySet in interface Map
        Specified by:
        entrySet in class AbstractMap
        Returns:
        a collection view of the mappings contained in this map.
        See Also:
        Map.Entry