Package org.apache.commons.collections4.map

Class TransformedMap<K,V>

java.lang.Object

org.apache.commons.collections4.map.AbstractIterableMap<K,V>

org.apache.commons.collections4.map.AbstractMapDecorator<K,V>

org.apache.commons.collections4.map.AbstractInputCheckedMapDecorator<K,V>

org.apache.commons.collections4.map.TransformedMap<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>, Get<K,V>, IterableGet<K,V>, IterableMap<K,V>, Put<K,V>

Direct Known Subclasses:

TransformedSortedMap

public class TransformedMap<K,V>
extends AbstractInputCheckedMapDecorator<K,V>
implements 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.

This class is Serializable from Commons Collections 3.1.

Since:

3.0

See Also:

• TransformedSplitMap
• Serialized Form

Nested Class Summary

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

Map.Entry<K,V>

Field Summary

Fields

Modifier and Type	Field	Description
protected final Transformer<? super K,? extends K>	keyTransformer	The transformer to use for the key
private static final long	serialVersionUID	Serialization version
protected final Transformer<? super V,? extends V>	valueTransformer	The transformer to use for the value

Fields inherited from class org.apache.commons.collections4.map.AbstractMapDecorator

map

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
protected V	checkSetValue(V value)	Override to transform the value when using setValue.
protected boolean	isSetValueChecking()	Override to only return true when there is a value transformer.
V	put(K key, V value)	Note that the return type is Object, rather than V as in the Map interface.
void	putAll(Map<? extends K,? extends V> mapToCopy)
private void	readObject(ObjectInputStream in)	Read the map in using a custom routine.
static <K, V> TransformedMap<K,V>	transformedMap(Map<K,V> map, Transformer<? super K,? extends K> keyTransformer, Transformer<? super V,? extends V> valueTransformer)	Factory method to create a transforming map that will transform existing contents of the specified map.
static <K, V> TransformedMap<K,V>	transformingMap(Map<K,V> map, Transformer<? super K,? extends K> keyTransformer, Transformer<? super V,? extends V> valueTransformer)	Factory method to create a transforming map.
protected K	transformKey(K object)	Transforms a key.
protected Map<K,V>	transformMap(Map<? extends K,? extends V> map)	Transforms a map.
protected V	transformValue(V object)	Transforms a value.
private void	writeObject(ObjectOutputStream out)	Write the map out using a custom routine.

Methods inherited from class org.apache.commons.collections4.map.AbstractInputCheckedMapDecorator

entrySet

Methods inherited from class org.apache.commons.collections4.map.AbstractMapDecorator

clear, containsKey, containsValue, decorated, equals, get, hashCode, isEmpty, keySet, remove, size, toString, values

Methods inherited from class org.apache.commons.collections4.map.AbstractIterableMap

mapIterator

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Field Details

serialVersionUID

private static final long serialVersionUID

Serialization version

See Also:

• Constant Field Values

keyTransformer

protected final Transformer<? super K,? extends K> keyTransformer

The transformer to use for the key

valueTransformer

protected final Transformer<? super V,? extends V> valueTransformer

The transformer to use for the value

Constructor Details

TransformedMap

protected TransformedMap(Map<K,V> map,
 Transformer<? super K,? extends K> keyTransformer,
 Transformer<? super V,? 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, null means no conversion

valueTransformer - the transformer to use for value conversion, null means no conversion

Throws:

NullPointerException - if map is null

Method Details

transformingMap

public static <K,
V> TransformedMap<K,V> transformingMap(Map<K,V> map,
 Transformer<? super K,? extends K> keyTransformer,
 Transformer<? super V,? 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. Contrast this with transformedMap(Map, Transformer, Transformer).

Type Parameters:

K - the key type

V - the value type

Parameters:

map - the map to decorate, must not be null

keyTransformer - the transformer to use for key conversion, null means no transformation

valueTransformer - the transformer to use for value conversion, null means no transformation

Returns:

a new transformed map

Throws:

NullPointerException - if map is null

Since:

4.0

transformedMap

public static <K,
V> TransformedMap<K,V> transformedMap(Map<K,V> map,
 Transformer<? super K,? extends K> keyTransformer,
 Transformer<? super V,? extends V> valueTransformer)

Factory method to create a transforming map that will transform existing contents of the specified map.

If there are any elements already in the map being decorated, they will be transformed by this method. Contrast this with transformingMap(Map, Transformer, Transformer).

Type Parameters:

K - the key type

V - the value type

Parameters:

map - the map to decorate, must not be null

keyTransformer - the transformer to use for key conversion, null means no transformation

valueTransformer - the transformer to use for value conversion, null means no transformation

Returns:

a new transformed map

Throws:

NullPointerException - if map is null

Since:

4.0

writeObject

private void writeObject(ObjectOutputStream out)
                  throws IOException

Write the map out using a custom routine.

Parameters:

out - the output stream

Throws:

IOException - if an error occurs while writing to the stream

Since:

3.1

readObject

private void readObject(ObjectInputStream in)
                 throws IOException,
ClassNotFoundException

Read the map in using a custom routine.

Parameters:

in - the input stream

Throws:

IOException - if an error occurs while reading from the stream

ClassNotFoundException - if an object read from the stream can not be loaded

Since:

3.1

transformKey

protected K transformKey(K 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(V 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 K,? extends V> 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(V value)

Override to transform the value when using setValue.

Specified by:

checkSetValue in class AbstractInputCheckedMapDecorator<K,V>

Parameters:

value - the value to transform

Returns:

the transformed value

Since:

3.1

isSetValueChecking

protected boolean isSetValueChecking()

Override to only return true when there is a value transformer.

Overrides:

isSetValueChecking in class AbstractInputCheckedMapDecorator<K,V>

Returns:

true if a value transformer is in use

Since:

3.1

put

public V put(K key,
 V 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 Map<K,V>

Specified by:

put in interface Put<K,V>

Overrides:

put in class AbstractMapDecorator<K,V>

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 K,? extends V> mapToCopy)

Specified by:

putAll in interface Map<K,V>

Specified by:

putAll in interface Put<K,V>

Overrides:

putAll in class AbstractMapDecorator<K,V>

Parameters:

mapToCopy - mappings to be stored in this map

See Also:

• Map.putAll(Map)