Package org.apache.commons.collections4.map

Class LazySortedMap<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>, SortedMap<K,​V>, Get<K,​V>, IterableGet<K,​V>, IterableMap<K,​V>, Put<K,​V>
    public class LazySortedMap<K,​V>
extends LazyMap<K,​V>
implements SortedMap<K,​V>
    Decorates another SortedMap to create objects in the map on demand.

    When the LazyMap.get(Object) method is called with a key that does not exist in the map, the factory is used to create the object. The created object will be added to the map using the requested key.

    For instance: 

     Factory<Date> factory = new Factory<Date>() {
     public Date create() {
         return new Date();
     }
 }
 SortedMap<String, Date> lazy =
     LazySortedMap.lazySortedMap(new HashMap<String, Date>(), factory);
 Date date = lazy.get("NOW");
    After the above code is executed, date will refer to a new Date instance. Furthermore, that Date instance is mapped to the "NOW" key in the map.

    Note that LazySortedMap 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.synchronizedSortedMap(java.util.SortedMap<K, V>). This class may throw exceptions when accessed by concurrent threads without synchronization.

    This class is Serializable from Commons Collections 3.1.

    Since:
    3.0
    See Also:
    Serialized Form

    • Constructor Detail

      • LazySortedMap

        protected LazySortedMap​(SortedMap<K,​V> map,
                        Factory<? extends V> factory)
        Constructor that wraps (not copies).
        Parameters:
        map - the map to decorate, must not be null
        factory - the factory to use, must not be null
        Throws:
        NullPointerException - if map or factory is null

      • LazySortedMap

        protected LazySortedMap​(SortedMap<K,​V> map,
                        Transformer<? super K,​? extends V> factory)
        Constructor that wraps (not copies).
        Parameters:
        map - the map to decorate, must not be null
        factory - the factory to use, must not be null
        Throws:
        NullPointerException - if map or factory is null

    • Method Detail

      • lazySortedMap

        public static <K,​V> LazySortedMap<K,​V> lazySortedMap​(SortedMap<K,​V> map,
                                                                 Factory<? extends V> factory)
        Factory method to create a lazily instantiated sorted map.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to decorate, must not be null
        factory - the factory to use, must not be null
        Returns:
        a new lazy sorted map
        Throws:
        NullPointerException - if map or factory is null
        Since:
        4.0

      • lazySortedMap

        public static <K,​V> LazySortedMap<K,​V> lazySortedMap​(SortedMap<K,​V> map,
                                                                 Transformer<? super K,​? extends V> factory)
        Factory method to create a lazily instantiated sorted map.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to decorate, must not be null
        factory - the factory to use, must not be null
        Returns:
        a new lazy sorted map
        Throws:
        NullPointerException - if map or factory is null
        Since:
        4.0

      • getSortedMap

        protected SortedMap<K,​V> getSortedMap()
        Gets the map being decorated.
        Returns:
        the decorated map