Class TreeBidiMap<K extends Comparable<K>, V extends Comparable<V>>

java.lang.Object
org.apache.commons.collections4.bidimap.TreeBidiMap<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:
Serializable, Map<K,V>, BidiMap<K,V>, Get<K,V>, IterableGet<K,V>, IterableMap<K,V>, OrderedBidiMap<K,V>, OrderedMap<K,V>, Put<K,V>
public class TreeBidiMap<K extends Comparable<K>, V extends Comparable<V>> extends Object implements OrderedBidiMap<K,V>, Serializable
Red-Black tree-based implementation of BidiMap where all objects added implement the Comparable interface.

This class guarantees that the map will be in both ascending key order and ascending value order, sorted according to the natural order for the key's and value's classes.

This Map is intended for applications that need to be able to look up a key-value pairing by either key or value, and need to do so with equal efficiency.

While that goal could be accomplished by taking a pair of TreeMaps and redirecting requests to the appropriate TreeMap (e.g., containsKey would be directed to the TreeMap that maps values to keys, containsValue would be directed to the TreeMap that maps keys to values), there are problems with that implementation. If the data contained in the TreeMaps is large, the cost of redundant storage becomes significant. The DualTreeBidiMap and DualHashBidiMap implementations use this approach.

This solution keeps minimizes the data storage by holding data only once. The red-black algorithm is based on TreeMap, but has been modified to simultaneously map a tree node by key and by value. This doubles the cost of put operations (but so does using two TreeMaps), and nearly doubles the cost of remove operations (there is a savings in that the lookup of the node to be removed only has to be performed once). And since only one node contains the key and value, storage is significantly less than that required by two TreeMaps.

The Map.Entry instances returned by the appropriate methods will not allow setValue() and will throw an UnsupportedOperationException on attempts to call that method.

Since:
3.0 (previously DoubleOrderedMap v2.0)
See Also:

  • Field Details

  • Constructor Details

    • TreeBidiMap

      public TreeBidiMap()
      Constructs a new empty TreeBidiMap.

    • TreeBidiMap

      public TreeBidiMap(Map<? extends K, ? extends V> map)
      Constructs a new TreeBidiMap by copying an existing Map.
      Parameters:
      map - the map to copy
      Throws:
      ClassCastException - if the keys/values in the map are not Comparable or are not mutually comparable
      NullPointerException - if any key or value in the map is null

  • Method Details

    • size

      public int size()
      Returns the number of key-value mappings in this map.
      Specified by:
      size in interface Get<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      size in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Returns:
      the number of key-value mappings in this map
      See Also:

    • isEmpty

      public boolean isEmpty()
      Checks whether the map is empty or not.
      Specified by:
      isEmpty in interface Get<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      isEmpty in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Returns:
      true if the map is empty
      See Also:

    • containsKey

      public boolean containsKey(Object key)
      Checks whether this map contains the a mapping for the specified key.

      The key must implement Comparable.

      Specified by:
      containsKey in interface Get<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      containsKey in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Parameters:
      key - key whose presence in this map is to be tested
      Returns:
      true if this map contains a mapping for the specified key
      Throws:
      ClassCastException - if the key is of an inappropriate type
      NullPointerException - if the key is null
      See Also:

    • containsValue

      public boolean containsValue(Object value)
      Checks whether this map contains the a mapping for the specified value.

      The value must implement Comparable.

      Specified by:
      containsValue in interface Get<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      containsValue in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Parameters:
      value - value whose presence in this map is to be tested
      Returns:
      true if this map contains a mapping for the specified value
      Throws:
      ClassCastException - if the value is of an inappropriate type
      NullPointerException - if the value is null
      See Also:

    • get

      public V get(Object key)
      Gets the value to which this map maps the specified key. Returns null if the map contains no mapping for this key.

      The key must implement Comparable.

      Specified by:
      get in interface Get<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      get in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Parameters:
      key - key whose associated value is to be returned
      Returns:
      the value to which this map maps the specified key, or null if the map contains no mapping for this key
      Throws:
      ClassCastException - if the key is of an inappropriate type
      NullPointerException - if the key is null
      See Also:

    • put

      public V put(K key, V value)
      Puts the key-value pair into the map, replacing any previous pair.

      When adding a key-value pair, the value may already exist in the map against a different key. That mapping is removed, to ensure that the value only occurs once in the inverse map. 

       BidiMap map1 = new TreeBidiMap();
 map.put("A","B");  // contains A mapped to B, as per Map
 map.put("A","C");  // contains A mapped to C, as per Map

 BidiMap map2 = new TreeBidiMap();
 map.put("A","B");  // contains A mapped to B, as per Map
 map.put("C","B");  // contains C mapped to B, key A is removed

      Both key and value must implement Comparable.

      Specified by:
      put in interface BidiMap<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      put in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      put in interface Put<K extends Comparable<K>, V extends Comparable<V>>
      Parameters:
      key - key with which the specified value is to be associated
      value - value to be associated with the specified key
      Returns:
      the previous value for the key
      Throws:
      ClassCastException - if the key is of an inappropriate type
      NullPointerException - if the key is null
      See Also:

    • putAll

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

      All keys and values must implement Comparable.

      Specified by:
      putAll in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      putAll in interface Put<K extends Comparable<K>, V extends Comparable<V>>
      Parameters:
      map - the map to copy from
      See Also:

    • remove

      public V remove(Object key)
      Removes the mapping for this key from this map if present.

      The key must implement Comparable.

      Specified by:
      remove in interface Get<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      remove in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      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.
      Throws:
      ClassCastException - if the key is of an inappropriate type
      NullPointerException - if the key is null
      See Also:

    • clear

      public void clear()
      Removes all mappings from this map.
      Specified by:
      clear in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      clear in interface Put<K extends Comparable<K>, V extends Comparable<V>>
      See Also:

    • getKey

      public K getKey(Object value)
      Returns the key to which this map maps the specified value. Returns null if the map contains no mapping for this value.

      The value must implement Comparable.

      Specified by:
      getKey in interface BidiMap<K extends Comparable<K>, V extends Comparable<V>>
      Parameters:
      value - value whose associated key is to be returned.
      Returns:
      the key to which this map maps the specified value, or null if the map contains no mapping for this value.
      Throws:
      ClassCastException - if the value is of an inappropriate type
      NullPointerException - if the value is null

    • removeValue

      public K removeValue(Object value)
      Removes the mapping for this value from this map if present.

      The value must implement Comparable.

      Specified by:
      removeValue in interface BidiMap<K extends Comparable<K>, V extends Comparable<V>>
      Parameters:
      value - value whose mapping is to be removed from the map
      Returns:
      previous key associated with specified value, or null if there was no mapping for value.
      Throws:
      ClassCastException - if the value is of an inappropriate type
      NullPointerException - if the value is null

    • firstKey

      public K firstKey()
      Gets the first (lowest) key currently in this map.
      Specified by:
      firstKey in interface OrderedMap<K extends Comparable<K>, V extends Comparable<V>>
      Returns:
      the first (lowest) key currently in this sorted map
      Throws:
      NoSuchElementException - if this map is empty

    • lastKey

      public K lastKey()
      Gets the last (highest) key currently in this map.
      Specified by:
      lastKey in interface OrderedMap<K extends Comparable<K>, V extends Comparable<V>>
      Returns:
      the last (highest) key currently in this sorted map
      Throws:
      NoSuchElementException - if this map is empty

    • nextKey

      public K nextKey(K key)
      Gets the next key after the one specified.

      The key must implement Comparable.

      Specified by:
      nextKey in interface OrderedMap<K extends Comparable<K>, V extends Comparable<V>>
      Parameters:
      key - the key to search for next from
      Returns:
      the next key, null if no match or at end

    • previousKey

      public K previousKey(K key)
      Gets the previous key before the one specified.

      The key must implement Comparable.

      Specified by:
      previousKey in interface OrderedMap<K extends Comparable<K>, V extends Comparable<V>>
      Parameters:
      key - the key to search for previous from
      Returns:
      the previous key, null if no match or at start

    • keySet

      public Set<K> keySet()
      Returns a set view of the keys contained in this map in key order.

      The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress, the results of the iteration are undefined.

      The set supports element removal, which removes the corresponding mapping from the map. It does not support the add or addAll operations.

      Specified by:
      keySet in interface Get<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      keySet in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Returns:
      a set view of the keys contained in this map.
      See Also:

    • values

      public Set<V> values()
      Returns a set view of the values contained in this map in key order. The returned object can be cast to a Set.

      The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress, the results of the iteration are undefined.

      The set supports element removal, which removes the corresponding mapping from the map. It does not support the add or addAll operations.

      Specified by:
      values in interface BidiMap<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      values in interface Get<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      values in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Returns:
      a set view of the values contained in this map.
      See Also:

    • entrySet

      public Set<Map.Entry<K,V>> entrySet()
      Returns a set view of the entries contained in this map in key order. For simple iteration through the map, the MapIterator is quicker.

      The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress, the results of the iteration are undefined.

      The set supports element removal, which removes the corresponding mapping from the map. It does not support the add or addAll operations. The returned MapEntry objects do not support setValue.

      Specified by:
      entrySet in interface Get<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      entrySet in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Returns:
      a set view of the values contained in this map.
      See Also:

    • mapIterator

      public OrderedMapIterator<K,V> mapIterator()
      Description copied from interface: IterableGet
      Obtains a MapIterator over the map.

      A map iterator is an efficient way of iterating over maps. There is no need to access the entry set or use Map Entry objects. 

      IterableMap<String,Integer> map = new HashedMap<String,Integer>();
MapIterator<String,Integer> it = map.mapIterator();
while (it.hasNext()) {
  String key = it.next();
  Integer value = it.getValue();
  it.setValue(value + 1);
}
      Specified by:
      mapIterator in interface IterableGet<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      mapIterator in interface OrderedMap<K extends Comparable<K>, V extends Comparable<V>>
      Returns:
      a map iterator

    • inverseBidiMap

      public OrderedBidiMap<V,K> inverseBidiMap()
      Gets the inverse map for comparison.
      Specified by:
      inverseBidiMap in interface BidiMap<K extends Comparable<K>, V extends Comparable<V>>
      Specified by:
      inverseBidiMap in interface OrderedBidiMap<K extends Comparable<K>, V extends Comparable<V>>
      Returns:
      the inverse map

    • equals

      public boolean equals(Object obj)
      Compares for equals as per the API.
      Specified by:
      equals in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Overrides:
      equals in class Object
      Parameters:
      obj - the object to compare to
      Returns:
      true if equal

    • hashCode

      public int hashCode()
      Gets the hash code value for this map as per the API.
      Specified by:
      hashCode in interface Map<K extends Comparable<K>, V extends Comparable<V>>
      Overrides:
      hashCode in class Object
      Returns:
      the hash code value for this map

    • toString

      public String toString()
      Returns a string version of this Map in standard format.
      Overrides:
      toString in class Object
      Returns:
      a standard format string version of the map

    • doPut

      private void doPut(K key, V value)
      Put logic.
      Parameters:
      key - the key, always the main map key
      value - the value, always the main map value

    • doRemoveKey

      private V doRemoveKey(Object key)

    • doRemoveValue

      private K doRemoveValue(Object value)

    • lookup

      private <T extends Comparable<T>> TreeBidiMap.Node<K,V> lookup(Object data, TreeBidiMap.DataElement dataElement)
      do the actual lookup of a piece of data
      Parameters:
      data - the key or value to be looked up
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.
      Returns:
      the desired Node, or null if there is no mapping of the specified data

    • lookupKey

      private TreeBidiMap.Node<K,V> lookupKey(Object key)

    • lookupValue

      private TreeBidiMap.Node<K,V> lookupValue(Object value)

    • nextGreater

      private TreeBidiMap.Node<K,V> nextGreater(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      get the next larger node from the specified node
      Parameters:
      node - the node to be searched from
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.
      Returns:
      the specified node

    • nextSmaller

      private TreeBidiMap.Node<K,V> nextSmaller(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      get the next larger node from the specified node
      Parameters:
      node - the node to be searched from
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.
      Returns:
      the specified node

    • compare

      private static <T extends Comparable<T>> int compare(T o1, T o2)
      Compare two objects
      Parameters:
      o1 - the first object
      o2 - the second object
      Returns:
      negative value if o1 < o2; 0 if o1 == o2; positive value if o1 > o2

    • leastNode

      private TreeBidiMap.Node<K,V> leastNode(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      Find the least node from a given node.
      Parameters:
      node - the node from which we will start searching
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.
      Returns:
      the smallest node, from the specified node, in the specified mapping

    • greatestNode

      private TreeBidiMap.Node<K,V> greatestNode(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      Find the greatest node from a given node.
      Parameters:
      node - the node from which we will start searching
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.
      Returns:
      the greatest node, from the specified node

    • copyColor

      private void copyColor(TreeBidiMap.Node<K,V> from, TreeBidiMap.Node<K,V> to, TreeBidiMap.DataElement dataElement)
      copy the color from one node to another, dealing with the fact that one or both nodes may, in fact, be null
      Parameters:
      from - the node whose color we're copying; may be null
      to - the node whose color we're changing; may be null
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • isRed

      private static boolean isRed(TreeBidiMap.Node<?,?> node, TreeBidiMap.DataElement dataElement)
      is the specified node red? if the node does not exist, no, it's black, thank you
      Parameters:
      node - the node (may be null) in question
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • isBlack

      private static boolean isBlack(TreeBidiMap.Node<?,?> node, TreeBidiMap.DataElement dataElement)
      is the specified black red? if the node does not exist, sure, it's black, thank you
      Parameters:
      node - the node (may be null) in question
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • makeRed

      private static void makeRed(TreeBidiMap.Node<?,?> node, TreeBidiMap.DataElement dataElement)
      force a node (if it exists) red
      Parameters:
      node - the node (may be null) in question
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • makeBlack

      private static void makeBlack(TreeBidiMap.Node<?,?> node, TreeBidiMap.DataElement dataElement)
      force a node (if it exists) black
      Parameters:
      node - the node (may be null) in question
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • getGrandParent

      private TreeBidiMap.Node<K,V> getGrandParent(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      get a node's grandparent. mind you, the node, its parent, or its grandparent may not exist. no problem
      Parameters:
      node - the node (may be null) in question
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • getParent

      private TreeBidiMap.Node<K,V> getParent(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      get a node's parent. mind you, the node, or its parent, may not exist. no problem
      Parameters:
      node - the node (may be null) in question
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • getRightChild

      private TreeBidiMap.Node<K,V> getRightChild(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      get a node's right child. mind you, the node may not exist. no problem
      Parameters:
      node - the node (may be null) in question
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • getLeftChild

      private TreeBidiMap.Node<K,V> getLeftChild(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      get a node's left child. mind you, the node may not exist. no problem
      Parameters:
      node - the node (may be null) in question
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • rotateLeft

      private void rotateLeft(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      do a rotate left. standard fare in the world of balanced trees
      Parameters:
      node - the node to be rotated
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • rotateRight

      private void rotateRight(TreeBidiMap.Node<K,V> node, TreeBidiMap.DataElement dataElement)
      do a rotate right. standard fare in the world of balanced trees
      Parameters:
      node - the node to be rotated
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.

    • doRedBlackInsert

      private void doRedBlackInsert(TreeBidiMap.Node<K,V> insertedNode, TreeBidiMap.DataElement dataElement)
      complicated red-black insert stuff. Based on Sun's TreeMap implementation, though it's barely recognizable any more
      Parameters:
      insertedNode - the node to be inserted
      dataElement - the KEY or VALUE int

    • doRedBlackDelete

      private void doRedBlackDelete(TreeBidiMap.Node<K,V> deletedNode)
      complicated red-black delete stuff. Based on Sun's TreeMap implementation, though it's barely recognizable any more
      Parameters:
      deletedNode - the node to be deleted

    • doRedBlackDeleteFixup

      private void doRedBlackDeleteFixup(TreeBidiMap.Node<K,V> replacementNode, TreeBidiMap.DataElement dataElement)
      complicated red-black delete stuff. Based on Sun's TreeMap implementation, though it's barely recognizable any more. This rebalances the tree (somewhat, as red-black trees are not perfectly balanced -- perfect balancing takes longer)
      Parameters:
      replacementNode - the node being replaced
      dataElement - the KEY or VALUE int

    • swapPosition

      private void swapPosition(TreeBidiMap.Node<K,V> x, TreeBidiMap.Node<K,V> y, TreeBidiMap.DataElement dataElement)
      swap two nodes (except for their content), taking care of special cases where one is the other's parent ... hey, it happens.
      Parameters:
      x - one node
      y - another node
      dataElement - the KEY or VALUE int

    • checkNonNullComparable

      private static void checkNonNullComparable(Object o, TreeBidiMap.DataElement dataElement)
      check if an object is fit to be proper input ... has to be Comparable and non-null
      Parameters:
      o - the object being checked
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.
      Throws:
      NullPointerException - if o is null
      ClassCastException - if o is not Comparable

    • checkKey

      private static void checkKey(Object key)
      check a key for validity (non-null and implements Comparable)
      Parameters:
      key - the key to be checked
      Throws:
      NullPointerException - if key is null
      ClassCastException - if key is not Comparable

    • checkValue

      private static void checkValue(Object value)
      check a value for validity (non-null and implements Comparable)
      Parameters:
      value - the value to be checked
      Throws:
      NullPointerException - if value is null
      ClassCastException - if value is not Comparable

    • checkKeyAndValue

      private static void checkKeyAndValue(Object key, Object value)
      check a key and a value for validity (non-null and implements Comparable)
      Parameters:
      key - the key to be checked
      value - the value to be checked
      Throws:
      NullPointerException - if key or value is null
      ClassCastException - if key or value is not Comparable

    • modify

      private void modify()
      increment the modification count -- used to check for concurrent modification of the map through the map and through an Iterator from one of its Set or Collection views

    • grow

      private void grow()
      bump up the size and note that the map has changed

    • shrink

      private void shrink()
      decrement the size and note that the map has changed

    • insertValue

      private void insertValue(TreeBidiMap.Node<K,V> newNode) throws IllegalArgumentException
      insert a node by its value
      Parameters:
      newNode - the node to be inserted
      Throws:
      IllegalArgumentException - if the node already exists in the value mapping

    • doEquals

      private boolean doEquals(Object obj, TreeBidiMap.DataElement dataElement)
      Compares for equals as per the API.
      Parameters:
      obj - the object to compare to
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.
      Returns:
      true if equal

    • doHashCode

      private int doHashCode(TreeBidiMap.DataElement dataElement)
      Gets the hash code value for this map as per the API.
      Parameters:
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.
      Returns:
      the hash code value for this map

    • doToString

      private String doToString(TreeBidiMap.DataElement dataElement)
      Gets the string form of this map as per AbstractMap.
      Parameters:
      dataElement - either TreeBidiMap.DataElement.KEY key} or the value.
      Returns:
      the string form of this map

    • getMapIterator

      private MapIterator<?,?> getMapIterator(TreeBidiMap.DataElement dataElement)

    • readObject

      private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException
      Reads the content of the stream.
      Parameters:
      stream - the input stream
      Throws:
      IOException - if an error occurs while reading from the stream
      ClassNotFoundException - if an object read from the stream can not be loaded

    • writeObject

      private void writeObject(ObjectOutputStream stream) throws IOException
      Writes the content to the stream for serialization.
      Parameters:
      stream - the output stream
      Throws:
      IOException - if an error occurs while writing to the stream