# Class TransformedSplitMap<J,K,U,V>

java.lang.Object
org.apache.commons.collections4.splitmap.AbstractIterableGetMapDecorator<K,V>
org.apache.commons.collections4.splitmap.TransformedSplitMap<J,K,U,V>

Type Parameters:
  `J` - the type of the keys to put in this map
  `K` - the type of the keys to get in this map
  `U` - the type of the values to put in this map
  `V` - the type of the values to get in this map

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 `&gt;Object, Object&gt;`, 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 Summary

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

- ## Method Summary

  Modifier and Type
  Method
  Description
  `protected V`
  `checkSetValue(U value)`
  Override to transform the value when using `setValue`.
  `void`
  `clear()`
  Removes all of the mappings from this map.
  `V`
  `put(J key, U value)`
  Associates the specified value with the specified key in this map.
  `void`
  `putAll(Map<? extends J,? extends U> mapToCopy)`
  Copies all of the mappings from the specified map to this map.
  `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.
  `protected K`
  `transformKey(J object)`
  Transforms a key.
  `protected Map<K,V>`
  `transformMap(Map<? extends J,? extends U> map)`
  Transforms a map.
  `protected V`
  `transformValue(U object)`
  Transforms a value.

  ### Methods inherited from class org.apache.commons.collections4.splitmap.AbstractIterableGetMapDecorator

  `containsKey, containsValue, decorated, entrySet, equals, get, hashCode, isEmpty, keySet, mapIterator, remove, size, toString, values`

  ### Methods inherited from class java.lang.Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### 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 Details

  - ### 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

  - ### checkSetValue

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

  - ### clear

    public void clear()
    Description copied from interface: `Put`
    Removes all of the mappings from this map.
    Specified by:
      `clear` in interface `Put<J,K>`
    See Also:
      - `Map.clear()`

  - ### put

    public V put(J key, U value)
    Description copied from interface: `Put`
    Associates the specified value with the specified key in this map.

    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,K>`
    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 associated with `key`, or `null` if there was no mapping for `key`. (A `null` return can also indicate that the map previously associated `null` with `key`, if the implementation supports `null` values.)
    See Also:
      - `Map.put(Object, Object)`

  - ### putAll

    public void putAll(Map<? extends J,? extends U> mapToCopy)
    Description copied from interface: `Put`
    Copies all of the mappings from the specified map to this map.
    Specified by:
      `putAll` in interface `Put<J,K>`
    Parameters:
      `mapToCopy` - mappings to be stored in this map
    See Also:
      - `Map.putAll(Map)`

  - ### 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

  - ### 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

  - ### 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