Package org.apache.commons.collections4.map

Class AbstractHashedMap<K,​V>

  • Type Parameters:
    K - the type of the keys in this map
    V - the type of the values in this map
    All Implemented Interfaces:
    java.util.Map<K,​V>, Get<K,​V>, IterableGet<K,​V>, IterableMap<K,​V>, Put<K,​V>
    Direct Known Subclasses:
    AbstractLinkedMap, AbstractReferenceMap, CaseInsensitiveMap, HashedMap
    public class AbstractHashedMap<K,​V>
extends java.util.AbstractMap<K,​V>
implements IterableMap<K,​V>
    An abstract implementation of a hash-based map which provides numerous points for subclasses to override.

    This class implements all the features necessary for a subclass hash-based map. Key-value entries are stored in instances of the HashEntry class, which can be overridden and replaced. The iterators can similarly be replaced, without the need to replace the KeySet, EntrySet and Values view classes.

    Overridable methods are provided to change the default hashing behaviour, and to change how entries are added to and removed from the map. Hopefully, all you need for unusual subclasses is here.

    NOTE: From Commons Collections 3.1 this class extends AbstractMap. This is to provide backwards compatibility for ReferenceMap between v3.0 and v3.1. This extends clause will be removed in v5.0.

    Since:
    3.0

    • Nested Class Summary

      • Nested classes/interfaces inherited from class java.util.AbstractMap

        java.util.AbstractMap.SimpleEntry<K extends java.lang.Object,​V extends java.lang.Object>, java.util.AbstractMap.SimpleImmutableEntry<K extends java.lang.Object,​V extends java.lang.Object>

      • Nested classes/interfaces inherited from interface java.util.Map

        java.util.Map.Entry<K extends java.lang.Object,​V extends java.lang.Object>

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()
      Clears the map, resetting the size to zero and nullifying references to avoid garbage collection issues.
      boolean containsKey​(java.lang.Object key)
      Checks whether the map contains the specified key.
      boolean containsValue​(java.lang.Object value)
      Checks whether the map contains the specified value.
      java.util.Set<java.util.Map.Entry<K,​V>> entrySet()
      Gets the entrySet view of the map.
      boolean equals​(java.lang.Object obj)
      Compares this map with another.
      V get​(java.lang.Object key)
      Gets the value mapped to the key specified.
      int hashCode()
      Gets the standard Map hashCode.
      boolean isEmpty()
      Checks whether the map is currently empty.
      java.util.Set<K> keySet()
      Gets the keySet view of the map.
      MapIterator<K,​V> mapIterator()
      Gets an iterator over the map.
      V put​(K key, V value)
      Puts a key-value mapping into this map.
      void putAll​(java.util.Map<? extends K,​? extends V> map)
      Puts all the values from the specified map into this map.
      V remove​(java.lang.Object key)
      Removes the specified mapping from this map.
      int size()
      Gets the size of the map.
      java.lang.String toString()
      Gets the map as a String.
      java.util.Collection<V> values()
      Gets the values view of the map.

      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.Map

        compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

    • Method Detail

      • get

        public V get​(java.lang.Object key)
        Gets the value mapped to the key specified.
        Specified by:
        get in interface Get<K,​V>
        Specified by:
        get in interface java.util.Map<K,​V>
        Overrides:
        get in class java.util.AbstractMap<K,​V>
        Parameters:
        key - the key
        Returns:
        the mapped value, null if no match
        See Also:
        Map.get(Object)

      • size

        public int size()
        Gets the size of the map.
        Specified by:
        size in interface Get<K,​V>
        Specified by:
        size in interface java.util.Map<K,​V>
        Overrides:
        size in class java.util.AbstractMap<K,​V>
        Returns:
        the size
        See Also:
        Map.size()

      • isEmpty

        public boolean isEmpty()
        Checks whether the map is currently empty.
        Specified by:
        isEmpty in interface Get<K,​V>
        Specified by:
        isEmpty in interface java.util.Map<K,​V>
        Overrides:
        isEmpty in class java.util.AbstractMap<K,​V>
        Returns:
        true if the map is currently size zero
        See Also:
        Map.isEmpty()

      • containsKey

        public boolean containsKey​(java.lang.Object key)
        Checks whether the map contains the specified key.
        Specified by:
        containsKey in interface Get<K,​V>
        Specified by:
        containsKey in interface java.util.Map<K,​V>
        Overrides:
        containsKey in class java.util.AbstractMap<K,​V>
        Parameters:
        key - the key to search for
        Returns:
        true if the map contains the key
        See Also:
        Map.containsKey(Object)

      • containsValue

        public boolean containsValue​(java.lang.Object value)
        Checks whether the map contains the specified value.
        Specified by:
        containsValue in interface Get<K,​V>
        Specified by:
        containsValue in interface java.util.Map<K,​V>
        Overrides:
        containsValue in class java.util.AbstractMap<K,​V>
        Parameters:
        value - the value to search for
        Returns:
        true if the map contains the value
        See Also:
        Map.containsValue(Object)

      • put

        public V put​(K key,
             V value)
        Puts a key-value mapping into this map.
        Specified by:
        put in interface java.util.Map<K,​V>
        Specified by:
        put in interface Put<K,​V>
        Overrides:
        put in class java.util.AbstractMap<K,​V>
        Parameters:
        key - the key to add
        value - the value to add
        Returns:
        the value previously mapped to this key, null if none
        See Also:
        Map.put(Object, Object)

      • putAll

        public void putAll​(java.util.Map<? extends K,​? extends V> map)
        Puts all the values from the specified map into this map.

        This implementation iterates around the specified map and uses put(Object, Object).

        Specified by:
        putAll in interface java.util.Map<K,​V>
        Specified by:
        putAll in interface Put<K,​V>
        Overrides:
        putAll in class java.util.AbstractMap<K,​V>
        Parameters:
        map - the map to add
        Throws:
        java.lang.NullPointerException - if the map is null
        See Also:
        Map.putAll(Map)

      • remove

        public V remove​(java.lang.Object key)
        Removes the specified mapping from this map.
        Specified by:
        remove in interface Get<K,​V>
        Specified by:
        remove in interface java.util.Map<K,​V>
        Overrides:
        remove in class java.util.AbstractMap<K,​V>
        Parameters:
        key - the mapping to remove
        Returns:
        the value mapped to the removed key, null if key not in map
        See Also:
        Map.remove(Object)

      • clear

        public void clear()
        Clears the map, resetting the size to zero and nullifying references to avoid garbage collection issues.
        Specified by:
        clear in interface java.util.Map<K,​V>
        Specified by:
        clear in interface Put<K,​V>
        Overrides:
        clear in class java.util.AbstractMap<K,​V>
        See Also:
        Map.clear()

      • mapIterator

        public MapIterator<K,​V> mapIterator()
        Gets an iterator over the map. Changes made to the iterator affect this map.

        A MapIterator returns the keys in the map. It also provides convenient methods to get the key and value, and set the value. It avoids the need to create an entrySet/keySet/values object. It also avoids creating the Map.Entry object.

        Specified by:
        mapIterator in interface IterableGet<K,​V>
        Returns:
        the map iterator

      • entrySet

        public java.util.Set<java.util.Map.Entry<K,​V>> entrySet()
        Gets the entrySet view of the map. Changes made to the view affect this map. To simply iterate through the entries, use mapIterator().
        Specified by:
        entrySet in interface Get<K,​V>
        Specified by:
        entrySet in interface java.util.Map<K,​V>
        Specified by:
        entrySet in class java.util.AbstractMap<K,​V>
        Returns:
        the entrySet view
        See Also:
        Map.entrySet()

      • keySet

        public java.util.Set<K> keySet()
        Gets the keySet view of the map. Changes made to the view affect this map. To simply iterate through the keys, use mapIterator().
        Specified by:
        keySet in interface Get<K,​V>
        Specified by:
        keySet in interface java.util.Map<K,​V>
        Overrides:
        keySet in class java.util.AbstractMap<K,​V>
        Returns:
        the keySet view
        See Also:
        Map.keySet()

      • values

        public java.util.Collection<V> values()
        Gets the values view of the map. Changes made to the view affect this map. To simply iterate through the values, use mapIterator().
        Specified by:
        values in interface Get<K,​V>
        Specified by:
        values in interface java.util.Map<K,​V>
        Overrides:
        values in class java.util.AbstractMap<K,​V>
        Returns:
        the values view
        See Also:
        Map.values()

      • equals

        public boolean equals​(java.lang.Object obj)
        Compares this map with another.
        Specified by:
        equals in interface java.util.Map<K,​V>
        Overrides:
        equals in class java.util.AbstractMap<K,​V>
        Parameters:
        obj - the object to compare to
        Returns:
        true if equal

      • hashCode

        public int hashCode()
        Gets the standard Map hashCode.
        Specified by:
        hashCode in interface java.util.Map<K,​V>
        Overrides:
        hashCode in class java.util.AbstractMap<K,​V>
        Returns:
        the hash code defined in the Map interface

      • toString

        public java.lang.String toString()
        Gets the map as a String.
        Overrides:
        toString in class java.util.AbstractMap<K,​V>
        Returns:
        a string version of the map