org.organicdesign.fp

Class FunctionUtils.UnmodifiableMap<K,V>

java.lang.Object

org.organicdesign.fp.FunctionUtils.UnmodifiableMap<K,V>

All Implemented Interfaces:

Serializable, Iterable<UnmodMap.UnEntry<K,V>>, Map<K,V>, Sized, UnmodIterable<UnmodMap.UnEntry<K,V>>, UnmodMap<K,V>, Transformable<UnmodMap.UnEntry<K,V>>

Enclosing class:

FunctionUtils

public static class FunctionUtils.UnmodifiableMap<K,V>
extends Object
implements UnmodMap<K,V>, Serializable

Wraps a map. The result will be serializable to the extent that the wrapped map is. You probably want to use this by calling FunctionUtils.unmodMap(Map).

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.organicdesign.fp.collections.UnmodMap

UnmodMap.AbstractUnmodMap<K,V>, UnmodMap.UnEntry<K,V>

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

Map.Entry<K,V>

Nested classes/interfaces inherited from interface org.organicdesign.fp.collections.UnmodIterable

UnmodIterable.AbstractUnmodIterable<T>

Method Summary

Modifier and Type	Method and Description
boolean	containsKey(Object key)
boolean	containsValue(Object value) Most maps are not designed for this - the default implementation has O(n) performance.
UnmodSet<Map.Entry<K,V>>	entrySet() Returns a view of the mappings contained in this map.
boolean	equals(Object o)
V	get(Object key)
int	hashCode()
boolean	isEmpty()
UnmodIterator<UnmodMap.UnEntry<K,V>>	iterator() A one-time use, mutable, not-thread-safe way to get each value of the underling collection in turn.
UnmodSet<K>	keySet() Returns a view of the keys contained in this map.
int	size() Returns the number of items in this iterable.
String	toString()
UnmodCollection<V>	values() Deprecated.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.organicdesign.fp.collections.UnmodMap

clear, compute, computeIfAbsent, computeIfPresent, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll

Methods inherited from interface java.util.Map

forEach, getOrDefault

Methods inherited from interface org.organicdesign.fp.collections.UnmodIterable

concat, drop, filter, flatMap, foldLeft, foldLeft, hash, hashCode, head, map, precat, take, takeWhile, toString

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Methods inherited from interface org.organicdesign.fp.xform.Transformable

toImList, toImMap, toImSet, toImSortedMap, toImSortedSet, toMutableList, toMutableMap, toMutableSet, toMutableSortedMap, toMutableSortedSet

Method Detail

iterator

public UnmodIterator<UnmodMap.UnEntry<K,V>> iterator()

A one-time use, mutable, not-thread-safe way to get each value of the underling collection in turn. I experimented with various thread-safe alternatives, but the JVM is optimized around iterators so this is the lowest common denominator of collection iteration, even though iterators are inherently mutable.

Specified by:

iterator in interface Iterable<UnmodMap.UnEntry<K,V>>

Specified by:

iterator in interface UnmodIterable<UnmodMap.UnEntry<K,V>>

entrySet

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

Description copied from interface: UnmodMap

Returns a view of the mappings contained in this map. The set will contain UnmodMap.UnEntry items, but that return signature is illegal in Java, so you'll just have to remember. An UnmodMap is iterable, so this method is probably not nearly as useful as it once was.

Specified by:

entrySet in interface Map<K,V>

Specified by:

entrySet in interface UnmodMap<K,V>

size

public int size()

Description copied from interface: Sized

Returns the number of items in this iterable.

Specified by:

size in interface Map<K,V>

Specified by:

size in interface Sized

isEmpty

public boolean isEmpty()

Description copied from interface: UnmodMap

Specified by:

isEmpty in interface Map<K,V>

Specified by:

isEmpty in interface UnmodMap<K,V>

containsKey

public boolean containsKey(Object key)

Specified by:

containsKey in interface Map<K,V>

containsValue

public boolean containsValue(Object value)

Description copied from interface: UnmodMap

Most maps are not designed for this - the default implementation has O(n) performance.

Specified by:

containsValue in interface Map<K,V>

Specified by:

containsValue in interface UnmodMap<K,V>

get

public V get(Object key)

Specified by:

get in interface Map<K,V>

keySet

public UnmodSet<K> keySet()

Description copied from interface: UnmodMap

Returns a view of the keys contained in this map. An UnmodMap is iterable, so this method is probably not nearly as useful as it once was.

Specified by:

keySet in interface Map<K,V>

Specified by:

keySet in interface UnmodMap<K,V>

values

@Deprecated
public UnmodCollection<V> values()

Deprecated.

Description copied from interface: UnmodMap

This method has been deprecated because it is impossible to implement equals() or hashCode() on the resulting collection, and calling this method is probably at least a missed opportunity, if not an outright error. Use an UnmodMap as an UnmodIterable<UnmodMap.UnEntry> instead. If you don't care about eliminating duplicate values, and want a compatible return type call:

myMap.map((UnEntry<K,V> entry) -> entry.getValue())
             .toImSet();

If you want to keep a count of duplicates, try something like this, but it has a different signature:

ImMap<V,Integer> valueCounts = myMap.foldLeft(PersistentHashMap.empty(),
                     (ImMap<V,Integer> accum, UnEntry<K,V> origEntry) -> {
                             V inVal = origEntry.getValue();
                             return accum.assoc(inVal,
                                                accum.getOrElse(inVal, 0) + 1);
                         });

You really shouldn't turn values() into a List, because a List has order and an unsorted Map is unordered by key, and especially unordered by value. On a SortedMap, List is the proper return type. java.util.HashMap.values() returns an instance of java.util.HashMap.Values which does *not* have equals() or hashCode() defined. This is because List.equals() and Set.equals() return not-equal when compared to a Collection. There is no good way to implement a reflexive equals with both of those because they are just too different. Ultimately, Collection just isn't specific enough to instantiate, but we do it anyway here for backward compatibility. We don't implement equals() or hashCode() either because the result could have duplicates. If the Map isn't sorted, the result could have random ordering.

Specified by:

values in interface Map<K,V>

Specified by:

values in interface UnmodMap<K,V>

hashCode

public int hashCode()

Specified by:

hashCode in interface Map<K,V>

Overrides:

hashCode in class Object

equals

public boolean equals(Object o)

Specified by:

equals in interface Map<K,V>

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object