Package org.apache.commons.collections

Class SequencedHashMap

java.lang.Object
org.apache.commons.collections.SequencedHashMap
All Implemented Interfaces:
Externalizable, Serializable, Cloneable, Map
Direct Known Subclasses:
LRUMap
public class SequencedHashMap extends Object implements Map, Cloneable, Externalizable
Deprecated.
Replaced by LinkedMap and ListOrderedMap in map subpackage. Due to be removed in v4.0.
A map of objects whose mapping entries are sequenced based on the order in which they were added. This data structure has fast O(1) search time, deletion time, and insertion time.

Although this map is sequenced, it cannot implement List because of incompatible interface definitions. The remove methods in List and Map have different return values (see: List.remove(Object) and Map.remove(Object)).

This class is not thread safe. When a thread safe implementation is required, use Collections.synchronizedMap(Map) as it is documented, or use explicit synchronization controls.

Since:
Commons Collections 2.0
Version:
$Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
See Also:

  • Field Details

    • sentinel

      private SequencedHashMap.Entry sentinel
      Deprecated.
      Sentinel used to hold the head and tail of the list of entries.

    • entries

      private HashMap entries
      Deprecated.
      Map of keys to entries

    • modCount

      private transient long modCount
      Deprecated.
      Holds the number of modifications that have occurred to the map, excluding modifications made through a collection view's iterator (e.g. entrySet().iterator().remove()). This is used to create a fail-fast behavior with the iterators.

    • KEY

      private static final int KEY
      Deprecated.
      See Also:

    • VALUE

      private static final int VALUE
      Deprecated.
      See Also:

    • ENTRY

      private static final int ENTRY
      Deprecated.
      See Also:

    • REMOVED_MASK

      private static final int REMOVED_MASK
      Deprecated.
      See Also:

    • serialVersionUID

      private static final long serialVersionUID
      Deprecated.
      See Also:

  • Constructor Details

    • SequencedHashMap

      public SequencedHashMap()
      Deprecated.
      Construct a new sequenced hash map with default initial size and load factor.

    • SequencedHashMap

      public SequencedHashMap(int initialSize)
      Deprecated.
      Construct a new sequenced hash map with the specified initial size and default load factor.
      Parameters:
      initialSize - the initial size for the hash table
      See Also:

    • SequencedHashMap

      public SequencedHashMap(int initialSize, float loadFactor)
      Deprecated.
      Construct a new sequenced hash map with the specified initial size and load factor.
      Parameters:
      initialSize - the initial size for the hash table
      loadFactor - the load factor for the hash table.
      See Also:

    • SequencedHashMap

      public SequencedHashMap(Map m)
      Deprecated.
      Construct a new sequenced hash map and add all the elements in the specified map. The order in which the mappings in the specified map are added is defined by putAll(Map).

  • Method Details

    • createSentinel

      private static final SequencedHashMap.Entry createSentinel()
      Deprecated.
      Construct an empty sentinel used to hold the head (sentinel.next) and the tail (sentinel.prev) of the list. The sentinel has a null key and value.

    • removeEntry

      private void removeEntry(SequencedHashMap.Entry entry)
      Deprecated.
      Removes an internal entry from the linked list. This does not remove it from the underlying map.

    • insertEntry

      private void insertEntry(SequencedHashMap.Entry entry)
      Deprecated.
      Inserts a new internal entry to the tail of the linked list. This does not add the entry to the underlying map.

    • size

      public int size()
      Deprecated.
      Implements Map.size().
      Specified by:
      size in interface Map

    • isEmpty

      public boolean isEmpty()
      Deprecated.
      Implements Map.isEmpty().
      Specified by:
      isEmpty in interface Map

    • containsKey

      public boolean containsKey(Object key)
      Deprecated.
      Implements Map.containsKey(Object).
      Specified by:
      containsKey in interface Map

    • containsValue

      public boolean containsValue(Object value)
      Deprecated.
      Implements Map.containsValue(Object).
      Specified by:
      containsValue in interface Map

    • get

      public Object get(Object o)
      Deprecated.
      Implements Map.get(Object).
      Specified by:
      get in interface Map

    • getFirst

      public Map.Entry getFirst()
      Deprecated.
      Return the entry for the "oldest" mapping. That is, return the Map.Entry for the key-value pair that was first put into the map when compared to all the other pairings in the map. This behavior is equivalent to using entrySet().iterator().next(), but this method provides an optimized implementation.
      Returns:
      The first entry in the sequence, or null if the map is empty.

    • getFirstKey

      public Object getFirstKey()
      Deprecated.
      Return the key for the "oldest" mapping. That is, return the key for the mapping that was first put into the map when compared to all the other objects in the map. This behavior is equivalent to using getFirst().getKey(), but this method provides a slightly optimized implementation.
      Returns:
      The first key in the sequence, or null if the map is empty.

    • getFirstValue

      public Object getFirstValue()
      Deprecated.
      Return the value for the "oldest" mapping. That is, return the value for the mapping that was first put into the map when compared to all the other objects in the map. This behavior is equivalent to using getFirst().getValue(), but this method provides a slightly optimized implementation.
      Returns:
      The first value in the sequence, or null if the map is empty.

    • getLast

      public Map.Entry getLast()
      Deprecated.
      Return the entry for the "newest" mapping. That is, return the Map.Entry for the key-value pair that was first put into the map when compared to all the other pairings in the map. The behavior is equivalent to: 
          Object obj = null;
    Iterator iter = entrySet().iterator();
    while(iter.hasNext()) {
      obj = iter.next();
    }
    return (Map.Entry)obj;
      However, the implementation of this method ensures an O(1) lookup of the last key rather than O(n).
      Returns:
      The last entry in the sequence, or null if the map is empty.

    • getLastKey

      public Object getLastKey()
      Deprecated.
      Return the key for the "newest" mapping. That is, return the key for the mapping that was last put into the map when compared to all the other objects in the map. This behavior is equivalent to using getLast().getKey(), but this method provides a slightly optimized implementation.
      Returns:
      The last key in the sequence, or null if the map is empty.

    • getLastValue

      public Object getLastValue()
      Deprecated.
      Return the value for the "newest" mapping. That is, return the value for the mapping that was last put into the map when compared to all the other objects in the map. This behavior is equivalent to using getLast().getValue(), but this method provides a slightly optimized implementation.
      Returns:
      The last value in the sequence, or null if the map is empty.

    • put

      public Object put(Object key, Object value)
      Deprecated.
      Implements Map.put(Object, Object).
      Specified by:
      put in interface Map

    • remove

      public Object remove(Object key)
      Deprecated.
      Implements Map.remove(Object).
      Specified by:
      remove in interface Map

    • removeImpl

      private SequencedHashMap.Entry removeImpl(Object key)
      Deprecated.
      Fully remove an entry from the map, returning the old entry or null if there was no such entry with the specified key.

    • putAll

      public void putAll(Map t)
      Deprecated.
      Adds all the mappings in the specified map to this map, replacing any mappings that already exist (as per Map.putAll(Map)). The order in which the entries are added is determined by the iterator returned from Map.entrySet() for the specified map.
      Specified by:
      putAll in interface Map
      Parameters:
      t - the mappings that should be added to this map.
      Throws:
      NullPointerException - if t is null

    • clear

      public void clear()
      Deprecated.
      Implements Map.clear().
      Specified by:
      clear in interface Map

    • equals

      public boolean equals(Object obj)
      Deprecated.
      Implements Map.equals(Object).
      Specified by:
      equals in interface Map
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Deprecated.
      Implements Map.hashCode().
      Specified by:
      hashCode in interface Map
      Overrides:
      hashCode in class Object

    • toString

      public String toString()
      Deprecated.
      Provides a string representation of the entries within the map. The format of the returned string may change with different releases, so this method is suitable for debugging purposes only. If a specific format is required, use entrySet().iterator() and iterate over the entries in the map formatting them as appropriate.
      Overrides:
      toString in class Object

    • keySet

      public Set keySet()
      Deprecated.
      Implements Map.keySet().
      Specified by:
      keySet in interface Map

    • values

      public Collection values()
      Deprecated.
      Implements Map.values().
      Specified by:
      values in interface Map

    • entrySet

      public Set entrySet()
      Deprecated.
      Implements Map.entrySet().
      Specified by:
      entrySet in interface Map

    • clone

      public Object clone() throws CloneNotSupportedException
      Deprecated.
      Creates a shallow copy of this object, preserving the internal structure by copying only references. The keys and values themselves are not clone()'d. The cloned object maintains the same sequence.
      Overrides:
      clone in class Object
      Returns:
      A clone of this instance.
      Throws:
      CloneNotSupportedException - if clone is not supported by a subclass.

    • getEntry

      private Map.Entry getEntry(int index)
      Deprecated.
      Returns the Map.Entry at the specified index
      Throws:
      ArrayIndexOutOfBoundsException - if the specified index is < 0 or > the size of the map.

    • get

      public Object get(int index)
      Deprecated.
      Gets the key at the specified index.
      Parameters:
      index - the index to retrieve
      Returns:
      the key at the specified index, or null
      Throws:
      ArrayIndexOutOfBoundsException - if the index is < 0 or > the size of the map.

    • getValue

      public Object getValue(int index)
      Deprecated.
      Gets the value at the specified index.
      Parameters:
      index - the index to retrieve
      Returns:
      the value at the specified index, or null
      Throws:
      ArrayIndexOutOfBoundsException - if the index is < 0 or > the size of the map.

    • indexOf

      public int indexOf(Object key)
      Deprecated.
      Gets the index of the specified key.
      Parameters:
      key - the key to find the index of
      Returns:
      the index, or -1 if not found

    • iterator

      public Iterator iterator()
      Deprecated.
      Gets an iterator over the keys.
      Returns:
      an iterator over the keys

    • lastIndexOf

      public int lastIndexOf(Object key)
      Deprecated.
      Gets the last index of the specified key.
      Parameters:
      key - the key to find the index of
      Returns:
      the index, or -1 if not found

    • sequence

      public List sequence()
      Deprecated.
      Returns a List view of the keys rather than a set view. The returned list is unmodifiable. This is required because changes to the values of the list (using ListIterator.set(Object)) will effectively remove the value from the list and reinsert that value at the end of the list, which is an unexpected side effect of changing the value of a list. This occurs because changing the key, changes when the mapping is added to the map and thus where it appears in the list.

      An alternative to this method is to use keySet()

      Returns:
      The ordered list of keys.
      See Also:

    • remove

      public Object remove(int index)
      Deprecated.
      Removes the element at the specified index.
      Parameters:
      index - The index of the object to remove.
      Returns:
      The previous value corresponding the key, or null if none existed.
      Throws:
      ArrayIndexOutOfBoundsException - if the index is < 0 or > the size of the map.

    • readExternal

      public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
      Deprecated.
      Deserializes this map from the given stream.
      Specified by:
      readExternal in interface Externalizable
      Parameters:
      in - the stream to deserialize from
      Throws:
      IOException - if the stream raises it
      ClassNotFoundException - if the stream raises it

    • writeExternal

      public void writeExternal(ObjectOutput out) throws IOException
      Deprecated.
      Serializes this map to the given stream.
      Specified by:
      writeExternal in interface Externalizable
      Parameters:
      out - the stream to serialize to
      Throws:
      IOException - if the stream raises it