Package org.apache.sis.util.collection

Class DerivedMap<SK,SV,K,V>

java.lang.Object

java.util.AbstractMap<K,V>

org.apache.sis.util.collection.DerivedMap<SK,SV,K,V>

Type Parameters:

SK - the type of keys in the storage map.

SV - the type of values in the storage map.

K - the type of keys in this map.

V - the type of values in this map.

All Implemented Interfaces:

Serializable, Function<Map.Entry<SK,SV>,Map.Entry<K,V>>, Map<K,V>, ObjectConverter<Map.Entry<SK,SV>,Map.Entry<K,V>>

Direct Known Subclasses:

DerivedMap.InvertibleKey, DerivedMap.InvertibleValue

class DerivedMap<SK,SV,K,V>
extends AbstractMap<K,V>
implements ObjectConverter<Map.Entry<SK,SV>,Map.Entry<K,V>>, Serializable

A map whose keys and values are derived on-the-fly from another map. Conversions are performed when needed by the following methods:

• The iterators over the key set or entry set obtain the derived keys using the keyConverter.
• The iterators over the values or entry set obtain the derived values using the valueConverter.
• Queries (get, containsKey) and write operations (put, remove) obtain the storage values using the inverse of the above converters.

Constraints

• This map does not support null keys, since null is used as a sentinel value when no mapping from storage to this exists.
• Instances of this class are serializable if their underlying storage map is serializable.
• This class is not thread-safe.

Performance considerations

This class does not cache any value, since the storage map is presumed modifiable. If the storage map is known to be immutable, then sub-classes may consider to cache some values, especially the result of the size() method.

Since:

0.3

Version:

0.3

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static final class	DerivedMap.Invertible<SK,SV,K,V>	A DerivedMap used when both the keyConverter and valueConverter are invertible.
private static class	DerivedMap.InvertibleKey<SK,SV,K,V>	A DerivedMap used when the keyConverter is invertible.
private static final class	DerivedMap.InvertibleValue<SK,SV,K,V>	A DerivedMap used when the valueConverter is invertible.

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K extends Object,V extends Object>, AbstractMap.SimpleImmutableEntry<K extends Object,V extends Object>

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

Map.Entry<K extends Object,V extends Object>

Field Summary

Fields

Modifier and Type	Field	Description
private Set<Map.Entry<K,V>>	entrySet	Entry set.
protected final ObjectConverter<SK,K>	keyConverter	The converter from the storage to the derived keys.
private Set<K>	keySet	Key set.
private static final long	serialVersionUID	Serial number for inter-operability with different versions.
protected final Map<SK,SV>	storage	The storage map whose keys are derived from.
protected final ObjectConverter<SV,V>	valueConverter	The converter from the storage to the derived values.

Constructor Summary

Constructors

Modifier	Constructor	Description
private	DerivedMap(Map<SK,SV> storage, ObjectConverter<SK,K> keyConverter, ObjectConverter<SV,V> valueConverter)	Creates a new derived map from the specified storage map.

Method Summary

Modifier and Type	Method	Description
final Map.Entry<K,V>	apply(Map.Entry<SK,SV> entry)	Converts the given entry.
(package private) static <SK, SV, K, V> Map<K,V>	create(Map<SK,SV> storage, ObjectConverter<SK,K> keyConverter, ObjectConverter<SV,V> valueConverter)	Creates a new derived map from the specified storage map.
final Set<Map.Entry<K,V>>	entrySet()	Returns a set view of the mappings contained in this map.
final Class<Map.Entry<SK,SV>>	getSourceClass()	Returns the source class of the map entry converter.
final Class<Map.Entry<K,V>>	getTargetClass()	Returns the target class of the map entry converter.
ObjectConverter<Map.Entry<K,V>,Map.Entry<SK,SV>>	inverse()	To be defined in the DerivedMap.Invertible sub-class only.
boolean	isEmpty()	Returns true if this map contains no key-value mappings.
final Set<K>	keySet()	Returns a set view of the keys contained in this map.
final Set<FunctionProperty>	properties()	Returns the properties of the entry converter, as the union of some properties of the key and value converters.
(package private) final V	put(K original, SK key, SV value)	Implementation of the put(Object,Object) method storing the given converted entry to the storage map.
V	put(K key, V value)	Associates the specified value with the specified key in this map.
int	size()	Returns the number of entries in this map.

Methods inherited from class java.util.AbstractMap

clear, clone, containsKey, containsValue, equals, get, hashCode, putAll, remove, toString, values

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.function.Function

andThen, compose

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

Serial number for inter-operability with different versions.

See Also:

• Constant Field Values

storage

protected final Map<SK,SV> storage

The storage map whose keys are derived from.

keyConverter

protected final ObjectConverter<SK,K> keyConverter

The converter from the storage to the derived keys.

valueConverter

protected final ObjectConverter<SV,V> valueConverter

The converter from the storage to the derived values.

keySet

private transient Set<K> keySet

Key set. Will be constructed only when first needed.

See Also:

• keySet()

entrySet

private transient Set<Map.Entry<K,V>> entrySet

Entry set. Will be constructed only when first needed.

See Also:

• entrySet()

Constructor Details

DerivedMap

private DerivedMap(Map<SK,SV> storage,
 ObjectConverter<SK,K> keyConverter,
 ObjectConverter<SV,V> valueConverter)

Creates a new derived map from the specified storage map.

Parameters:

storage - the map which actually store the entries.

keyConverter - the converter for the keys.

valueConverter - the converter for the values.

Method Details

create

static <SK,
SV,
K,
V> Map<K,V> create(Map<SK,SV> storage,
 ObjectConverter<SK,K> keyConverter,
 ObjectConverter<SV,V> valueConverter)

Creates a new derived map from the specified storage map.

Parameters:

storage - the map which actually store the entries.

keyConverter - the converter for the keys.

valueConverter - the converter for the values.

size

public int size()

Returns the number of entries in this map.

Specified by:

size in interface Map<SK,SV>

Overrides:

size in class AbstractMap<K,V>

Returns:

the number of entries in this map.

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Specified by:

isEmpty in interface Map<SK,SV>

Overrides:

isEmpty in class AbstractMap<K,V>

Returns:

true if this map contains no key-value mappings.

put

public V put(K key,
 V value)
      throws UnsupportedOperationException

Associates the specified value with the specified key in this map.

Specified by:

put in interface Map<SK,SV>

Overrides:

put in class AbstractMap<K,V>

Parameters:

key - key with which the specified value is to be associated.

value - value to be associated with the specified key.

Returns:

previous value associated with specified key, or null if there was no mapping for key.

Throws:

UnsupportedOperationException - if the converters are not invertible, or the storage map doesn't supports the put operation.

put

final V put(K original,
 SK key,
 SV value)

Implementation of the put(Object,Object) method storing the given converted entry to the storage map. The original key is used only for formatting an error message in case of failure.

keySet

public final Set<K> keySet()

Returns a set view of the keys contained in this map.

Specified by:

keySet in interface Map<SK,SV>

Overrides:

keySet in class AbstractMap<K,V>

Returns:

a view of the keys in this map.

entrySet

public final Set<Map.Entry<K,V>> entrySet()

Returns a set view of the mappings contained in this map.

Specified by:

entrySet in interface Map<SK,SV>

Specified by:

entrySet in class AbstractMap<K,V>

Returns:

a view of the entries in this map.

properties

public final Set<FunctionProperty> properties()

Returns the properties of the entry converter, as the union of some properties of the key and value converters.

Specified by:

properties in interface ObjectConverter<SK,SV>

Returns:

the manners in which source values are mapped to target values. May be an empty set, but never null.

getSourceClass

public final Class<Map.Entry<SK,SV>> getSourceClass()

Returns the source class of the map entry converter. Defined because the interface requires so but not used.

Specified by:

getSourceClass in interface ObjectConverter<SK,SV>

Returns:

the type of objects to convert.

getTargetClass

public final Class<Map.Entry<K,V>> getTargetClass()

Returns the target class of the map entry converter. Defined because the interface requires so but not used.

Specified by:

getTargetClass in interface ObjectConverter<SK,SV>

Returns:

the type of converted objects.

apply

public final Map.Entry<K,V> apply(Map.Entry<SK,SV> entry)

Converts the given entry.

Specified by:

apply in interface Function<SK,SV>

Specified by:

apply in interface ObjectConverter<SK,SV>

Parameters:

entry - an entry with the key and value from the storage.

Returns:

an entry with the key and value converted to types declared by this map, or null if the key is unconvertible.

inverse

public ObjectConverter<Map.Entry<K,V>,Map.Entry<SK,SV>> inverse()
                                                         throws UnsupportedOperationException

To be defined in the DerivedMap.Invertible sub-class only.

Specified by:

inverse in interface ObjectConverter<SK,SV>

Returns:

a converter for converting instances of T back to instances of S.

Throws:

UnsupportedOperationException - if this converter is not invertible.

See Also:

• FunctionProperty.INVERTIBLE