org.tenidwa.collections.utils

Class ContentMap<K,C,V>

java.lang.Object

org.tenidwa.collections.utils.ContentMap<K,C,V>

Type Parameters:

K - Key type

C - Some content obtainable from K

V - Value type

All Implemented Interfaces:

Map<K,V>

public final class ContentMap<K,C,V>
extends Object
implements Map<K,V>

Map that uses function of K as keys instead of K.

Its purpose is to allow mapping from keys that don't support Object.equals(Object). When using the usual Map that has an interface as a key type, there is no sane way to treat instances of different types as equal, because then we'd have to:

• re-implement Object.equals(Object) in every type (which would be a lot of duplicated code);
• or extend every implementation of the interface with an abstract class that implements Object.equals(Object) using methods of that interface (which would still be duplicating code, not per interface implementation but per interface).

"Content" in "ContentMap" means "something equatable that is obtained with public methods of interface K"

For example, if PersonWithoutEquals and PersonFromStream don't implement equals but have method Person#name() that returns String, we could map Persons to something else like this:

     Map map =
         new ContentMap(Person::name);
     map.put(new PersonWithoutEquals("Jeff"), 1);
     map.get(new PersonFromStream(streamWithNameJeff)); // 1
 

This map has deterministic ordering.

This map doesn't support methods Map.keySet() and Map.entrySet() because it doesn't store the keys of type K, it just uses those to obtain the "hidden" keys of type C.

Since:

0.6.0

Version:

$Id$

Author:

Georgy Vlasov (suseika@tendiwa.org)

Nested Class Summary

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

Map.Entry<K,V>

Constructor Summary

Constructors

Constructor and Description
ContentMap(Map<K,V> base, java.util.function.Function<K,C> function) Ctor.

Method Summary

Modifier and Type	Method and Description
void	clear() Deprecated.
boolean	containsKey(Object o)
boolean	containsValue(Object o)
Set<Map.Entry<K,V>>	entrySet() Deprecated.
V	get(Object o)
boolean	isEmpty()
Set<K>	keySet() Deprecated.
V	put(K k, V v) Deprecated.
void	putAll(Map<? extends K,? extends V> map) Deprecated.
V	remove(Object o) Deprecated.
int	size()
Collection<V>	values()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Map

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

Constructor Detail

ContentMap

public ContentMap(Map<K,V> base,
                  java.util.function.Function<K,C> function)

Ctor.

Parameters:

base - Base map.

function - Function to get content of a key.

Method Detail

size

public int size()

Specified by:

size in interface Map<K,V>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map<K,V>

containsKey

public boolean containsKey(Object o)

Specified by:

containsKey in interface Map<K,V>

containsValue

public boolean containsValue(Object o)

Specified by:

containsValue in interface Map<K,V>

get

public V get(Object o)

Specified by:

get in interface Map<K,V>

put

@Deprecated
public V put(K k,
                         V v)

Deprecated.

Specified by:

put in interface Map<K,V>

remove

@Deprecated
public V remove(Object o)

Deprecated.

Specified by:

remove in interface Map<K,V>

putAll

@Deprecated
public void putAll(Map<? extends K,? extends V> map)

Deprecated.

Specified by:

putAll in interface Map<K,V>

clear

@Deprecated
public void clear()

Deprecated.

Specified by:

clear in interface Map<K,V>

keySet

@Deprecated
public Set<K> keySet()

Deprecated.

Specified by:

keySet in interface Map<K,V>

values

public Collection<V> values()

Specified by:

values in interface Map<K,V>

entrySet

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

Deprecated.

Specified by:

entrySet in interface Map<K,V>