Package org.apache.commons.collections.map

Class ListOrderedMap

  • All Implemented Interfaces:
    java.io.Serializable, java.util.Map, IterableMap, OrderedMap
    public class ListOrderedMap
extends AbstractMapDecorator
implements OrderedMap, java.io.Serializable
    Decorates a Map to ensure that the order of addition is retained using a List to maintain order.

    The order will be used via the iterators and toArray methods on the views. The order is also returned by the MapIterator. The orderedMapIterator() method accesses an iterator that can iterate both forwards and backwards through the map. In addition, non-interface methods are provided to access the map by index.

    If an object is added to the Map for a second time, it will remain in the original position in the iteration.

    Note that ListOrderedMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. The simplest approach is to wrap this map using Collections.synchronizedMap(Map). This class may throw exceptions when accessed by concurrent threads without synchronization.

    This class is Serializable from Commons Collections 3.1.

    Since:
    Commons Collections 3.0
    See Also:
    Serialized Form

    • Nested Class Summary

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

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

    • Constructor Summary

      Constructors 
      Constructor Description
      ListOrderedMap()
      Constructs a new empty ListOrderedMap that decorates a HashMap.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.util.List asList()
      Gets an unmodifiable List view of the keys which changes as the map changes.
      void clear()  
      static OrderedMap decorate​(java.util.Map map)
      Factory method to create an ordered map.
      java.util.Set entrySet()
      Gets a view over the entries in the map.
      java.lang.Object firstKey()
      Gets the first key in this map by insert order.
      java.lang.Object get​(int index)
      Gets the key at the specified index.
      java.lang.Object getValue​(int index)
      Gets the value at the specified index.
      int indexOf​(java.lang.Object key)
      Gets the index of the specified key.
      java.util.List keyList()
      Gets a view over the keys in the map as a List.
      java.util.Set keySet()
      Gets a view over the keys in the map.
      java.lang.Object lastKey()
      Gets the last key in this map by insert order.
      MapIterator mapIterator()
      Obtains a MapIterator over the map.
      java.lang.Object nextKey​(java.lang.Object key)
      Gets the next key to the one specified using insert order.
      OrderedMapIterator orderedMapIterator()
      Obtains an OrderedMapIterator over the map.
      java.lang.Object previousKey​(java.lang.Object key)
      Gets the previous key to the one specified using insert order.
      java.lang.Object put​(int index, java.lang.Object key, java.lang.Object value)
      Puts a key-value mapping into the map at the specified index.
      java.lang.Object put​(java.lang.Object key, java.lang.Object value)  
      void putAll​(java.util.Map map)  
      java.lang.Object remove​(int index)
      Removes the element at the specified index.
      java.lang.Object remove​(java.lang.Object key)  
      java.lang.Object setValue​(int index, java.lang.Object value)
      Sets the value at the specified index.
      java.lang.String toString()
      Returns the Map as a string.
      java.util.List valueList()
      Gets a view over the values in the map as a List.
      java.util.Collection values()
      Gets a view over the values in 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, containsKey, containsValue, equals, forEach, get, getOrDefault, hashCode, isEmpty, merge, putIfAbsent, remove, replace, replace, replaceAll, size

    • Constructor Detail

      • ListOrderedMap

        public ListOrderedMap()
        Constructs a new empty ListOrderedMap that decorates a HashMap.
        Since:
        Commons Collections 3.1

    • Method Detail

      • decorate

        public static OrderedMap decorate​(java.util.Map map)
        Factory method to create an ordered map.

        An ArrayList is used to retain order.

        Parameters:
        map - the map to decorate, must not be null
        Throws:
        java.lang.IllegalArgumentException - if map is null

      • mapIterator

        public MapIterator mapIterator()
        Description copied from interface: IterableMap
        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 cast to Map Entry objects. 

         IterableMap map = new HashedMap();
 MapIterator it = map.mapIterator();
 while (it.hasNext()) {
   Object key = it.next();
   Object value = it.getValue();
   it.setValue("newValue");
 }
        Specified by:
        mapIterator in interface IterableMap
        Returns:
        a map iterator

      • orderedMapIterator

        public OrderedMapIterator orderedMapIterator()
        Description copied from interface: OrderedMap
        Obtains an OrderedMapIterator over the map.

        A ordered map iterator is an efficient way of iterating over maps in both directions. 

         BidiMap map = new TreeBidiMap();
 MapIterator it = map.mapIterator();
 while (it.hasNext()) {
   Object key = it.next();
   Object value = it.getValue();
   it.setValue("newValue");
   Object previousKey = it.previous();
 }
        Specified by:
        orderedMapIterator in interface OrderedMap
        Returns:
        a map iterator

      • firstKey

        public java.lang.Object firstKey()
        Gets the first key in this map by insert order.
        Specified by:
        firstKey in interface OrderedMap
        Returns:
        the first key currently in this map
        Throws:
        java.util.NoSuchElementException - if this map is empty

      • lastKey

        public java.lang.Object lastKey()
        Gets the last key in this map by insert order.
        Specified by:
        lastKey in interface OrderedMap
        Returns:
        the last key currently in this map
        Throws:
        java.util.NoSuchElementException - if this map is empty

      • nextKey

        public java.lang.Object nextKey​(java.lang.Object key)
        Gets the next key to the one specified using insert order. This method performs a list search to find the key and is O(n).
        Specified by:
        nextKey in interface OrderedMap
        Parameters:
        key - the key to find previous for
        Returns:
        the next key, null if no match or at start

      • previousKey

        public java.lang.Object previousKey​(java.lang.Object key)
        Gets the previous key to the one specified using insert order. This method performs a list search to find the key and is O(n).
        Specified by:
        previousKey in interface OrderedMap
        Parameters:
        key - the key to find previous for
        Returns:
        the previous key, null if no match or at start

      • put

        public java.lang.Object put​(java.lang.Object key,
                            java.lang.Object value)
        Specified by:
        put in interface java.util.Map
        Overrides:
        put in class AbstractMapDecorator

      • putAll

        public void putAll​(java.util.Map map)
        Specified by:
        putAll in interface java.util.Map
        Overrides:
        putAll in class AbstractMapDecorator

      • remove

        public java.lang.Object remove​(java.lang.Object key)
        Specified by:
        remove in interface java.util.Map
        Overrides:
        remove in class AbstractMapDecorator

      • clear

        public void clear()
        Specified by:
        clear in interface java.util.Map
        Overrides:
        clear in class AbstractMapDecorator

      • keySet

        public java.util.Set keySet()
        Gets a view over the keys in the map.

        The Collection will be ordered by object insertion into the map.

        Specified by:
        keySet in interface java.util.Map
        Overrides:
        keySet in class AbstractMapDecorator
        Returns:
        the fully modifiable collection view over the keys
        See Also:
        keyList()

      • keyList

        public java.util.List keyList()
        Gets a view over the keys in the map as a List.

        The List will be ordered by object insertion into the map. The List is unmodifiable.

        Returns:
        the unmodifiable list view over the keys
        Since:
        Commons Collections 3.2
        See Also:
        keySet()

      • values

        public java.util.Collection values()
        Gets a view over the values in the map.

        The Collection will be ordered by object insertion into the map.

        From Commons Collections 3.2, this Collection can be cast to a list, see valueList()

        Specified by:
        values in interface java.util.Map
        Overrides:
        values in class AbstractMapDecorator
        Returns:
        the fully modifiable collection view over the values
        See Also:
        valueList()

      • valueList

        public java.util.List valueList()
        Gets a view over the values in the map as a List.

        The List will be ordered by object insertion into the map. The List supports remove and set, but does not support add.

        Returns:
        the partially modifiable list view over the values
        Since:
        Commons Collections 3.2
        See Also:
        values()

      • entrySet

        public java.util.Set entrySet()
        Gets a view over the entries in the map.

        The Set will be ordered by object insertion into the map.

        Specified by:
        entrySet in interface java.util.Map
        Overrides:
        entrySet in class AbstractMapDecorator
        Returns:
        the fully modifiable set view over the entries

      • toString

        public java.lang.String toString()
        Returns the Map as a string.
        Overrides:
        toString in class AbstractMapDecorator
        Returns:
        the Map as a String

      • get

        public java.lang.Object get​(int index)
        Gets the key at the specified index.
        Parameters:
        index - the index to retrieve
        Returns:
        the key at the specified index
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is invalid

      • getValue

        public java.lang.Object getValue​(int index)
        Gets the value at the specified index.
        Parameters:
        index - the index to retrieve
        Returns:
        the key at the specified index
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is invalid

      • indexOf

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

      • setValue

        public java.lang.Object setValue​(int index,
                                 java.lang.Object value)
        Sets the value at the specified index.
        Parameters:
        index - the index of the value to set
        Returns:
        the previous value at that index
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is invalid
        Since:
        Commons Collections 3.2

      • put

        public java.lang.Object put​(int index,
                            java.lang.Object key,
                            java.lang.Object value)
        Puts a key-value mapping into the map at the specified index.

        If the map already contains the key, then the original mapping is removed and the new mapping added at the specified index. The remove may change the effect of the index. The index is always calculated relative to the original state of the map.

        Thus the steps are: (1) remove the existing key-value mapping, then (2) insert the new key-value mapping at the position it would have been inserted had the remove not ocurred.

        Parameters:
        index - the index at which the mapping should be inserted
        key - the key
        value - the value
        Returns:
        the value previously mapped to the key
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is out of range
        Since:
        Commons Collections 3.2

      • remove

        public java.lang.Object remove​(int index)
        Removes the element at the specified index.
        Parameters:
        index - the index of the object to remove
        Returns:
        the removed value, or null if none existed
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is invalid

      • asList

        public java.util.List asList()
        Gets an unmodifiable List view of the keys which changes as the map changes.

        The returned list is unmodifiable 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 the better named keyList() or keySet().

        Returns:
        The ordered list of keys.
        See Also:
        keyList(), keySet()