org.apache.commons.collections4.splitmap

Class TransformedSplitMap<J,K,U,V>

  • All Implemented Interfaces:
    Serializable, Get<K,V>, IterableGet<K,V>, Put<J,U> 

    public class TransformedSplitMap<J,K,U,V>
extends AbstractIterableGetMapDecorator<K,V>
implements Put<J,U>, Serializable
    Decorates another Map to transform objects that are added.

    The Map put methods and Map.Entry setValue method are affected by this class. Thus objects must be removed or searched for using their transformed form. For example, if the transformation converts Strings to Integers, you must use the Integer form to remove objects.

    Note that TransformedMap 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.

    The "put" and "get" type constraints of this class are mutually independent; contrast with TransformedMap which, by virtue of its implementing Map<K, V>, must be constructed in such a way that its read and write parameters are generalized to a common (super-)type. In practice this would often mean >Object, Object>, defeating much of the usefulness of having parameterized types.

    On the downside, this class is not drop-in compatible with Map but is intended to be worked with either directly or by Put and Get generalizations.

    Since:
    4.0
    See Also:
    SplitMapUtils.readableMap(org.apache.commons.collections4.Get), SplitMapUtils.writableMap(Put), Serialized Form

    • Constructor Detail

      • TransformedSplitMap

        protected TransformedSplitMap(Map<K,V> map,
                              Transformer<? super J,? extends K> keyTransformer,
                              Transformer<? super U,? extends V> valueTransformer)
        Constructor that wraps (not copies).

        If there are any elements already in the collection being decorated, they are NOT transformed.

        Parameters:
        map - the map to decorate, must not be null
        keyTransformer - the transformer to use for key conversion, must not be null
        valueTransformer - the transformer to use for value conversion, must not be null
        Throws:
        NullPointerException - if map or either of the transformers is null

    • Method Detail

      • transformingMap

        public static <J,K,U,V> TransformedSplitMap<J,K,U,V> transformingMap(Map<K,V> map,
                                                                     Transformer<? super J,? extends K> keyTransformer,
                                                                     Transformer<? super U,? extends V> valueTransformer)
        Factory method to create a transforming map.

        If there are any elements already in the map being decorated, they are NOT transformed.

        Type Parameters:
        J - the input key type
        K - the output key type
        U - the input value type
        V - the output value type
        Parameters:
        map - the map to decorate, must not be null
        keyTransformer - the transformer to use for key conversion, must not be null
        valueTransformer - the transformer to use for value conversion, must not be null
        Returns:
        a new transformed map
        Throws:
        NullPointerException - if map or either of the transformers is null

      • transformKey

        protected K transformKey(J object)
        Transforms a key.

        The transformer itself may throw an exception if necessary.

        Parameters:
        object - the object to transform
        Returns:
        the transformed object

      • transformValue

        protected V transformValue(U object)
        Transforms a value.

        The transformer itself may throw an exception if necessary.

        Parameters:
        object - the object to transform
        Returns:
        the transformed object

      • transformMap

        protected Map<K,V> transformMap(Map<? extends J,? extends U> map)
        Transforms a map.

        The transformer itself may throw an exception if necessary.

        Parameters:
        map - the map to transform
        Returns:
        the transformed object

      • checkSetValue

        protected V checkSetValue(U value)
        Override to transform the value when using setValue.
        Parameters:
        value - the value to transform
        Returns:
        the transformed value

      • put

        public V put(J key,
             U value)
        Description copied from interface: Put
        Note that the return type is Object, rather than V as in the Map interface. See the class Javadoc for further info.
        Specified by:
        put in interface  Put<J,U>
        See Also:
        Map.put(Object, Object)