Package org.apache.commons.collections4.splitmap

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 >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 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()
V	put(J key, U value)	Note that the return type is Object, rather than V as in the Map interface.
void	putAll(Map<? extends J,? extends U> mapToCopy)
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()

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

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)

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