Class DerivedKeyHashMap<K,V>
- java.lang.Object
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- com.github.andrewoma.dexx.collection.internal.base.AbstractTraversable<E>
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- com.github.andrewoma.dexx.collection.internal.base.AbstractIterable<Pair<K,V>>
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- com.github.andrewoma.dexx.collection.internal.base.AbstractMap<K,V>
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- com.github.andrewoma.dexx.collection.DerivedKeyHashMap<K,V>
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- All Implemented Interfaces:
Iterable<Pair<K,V>>
,Map<K,V>
,Traversable<Pair<K,V>>
,java.lang.Iterable<Pair<K,V>>
public class DerivedKeyHashMap<K,V> extends AbstractMap<K,V>
DerivedKeyHashMap
is aHashMap
variant where the key for theMap
is derived from the value stored.By deriving the key it is possible to reduce the memory overhead per node in the map (assuming the key is a primitive field in the value object). e.g.
static class Value { int key; int value; } DerivedKeyHashMap<Integer, Value> map = new DerivedKeyHashMap<Integer, Value>( new KeyFunction<Integer, Value>() { public Integer key(Value value) { return value.key; } }); Value value = new Value(); value.key = 1; value.value = 100; map = map.put(value.key, value);
It uses significantly less memory than Scala's implementation as the leaf nodes are the values themselves (not objects containing keys, values and hashes).
As the key is derived from the value,
DerivedKeyHashMap
does not supportnull
values.
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Field Summary
Fields Modifier and Type Field Description private CompactHashMap<K,V>
compactHashMap
private KeyFunction<K,V>
keyFunction
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Constructor Summary
Constructors Modifier Constructor Description DerivedKeyHashMap(@NotNull KeyFunction<K,V> keyFunction)
private
DerivedKeyHashMap(KeyFunction<K,V> keyFunction, CompactHashMap<K,V> compactHashMap)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
containsKey(K key)
Returns true if this map contains the specified key.static <K,V>
@NotNull BuilderFactory<Pair<K,V>,DerivedKeyHashMap<K,V>>factory(KeyFunction<K,V> keyFunction)
<U> void
forEach(@NotNull Function<Pair<K,V>,U> f)
All collection methods can be built upon thisforEach
definition.V
get(K key)
Returns the value associated with the key ornull
if the no value exists with the key specified.@NotNull java.util.Iterator<Pair<K,V>>
iterator()
@NotNull DerivedKeyHashMap<K,V>
put(K key, V value)
Returns a map with the value specified associated to the key specified.@NotNull DerivedKeyHashMap<K,V>
remove(K key)
Returns a map with the value associated with the key removed if it exists.int
size()
Returns the size of the collection.-
Methods inherited from class com.github.andrewoma.dexx.collection.internal.base.AbstractMap
asMap, equals, hashCode, keys, values
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Methods inherited from class com.github.andrewoma.dexx.collection.internal.base.AbstractTraversable
isEmpty, makeString, makeString, to, toArray, toArray, toIndexedList, toSet, toSortedSet, toString
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface com.github.andrewoma.dexx.collection.Traversable
isEmpty, makeString, makeString, to, toArray, toArray, toIndexedList, toSet, toSortedSet
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Field Detail
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keyFunction
private final KeyFunction<K,V> keyFunction
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compactHashMap
private final CompactHashMap<K,V> compactHashMap
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Constructor Detail
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DerivedKeyHashMap
public DerivedKeyHashMap(@NotNull @NotNull KeyFunction<K,V> keyFunction)
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DerivedKeyHashMap
private DerivedKeyHashMap(KeyFunction<K,V> keyFunction, CompactHashMap<K,V> compactHashMap)
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Method Detail
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factory
@NotNull public static <K,V> @NotNull BuilderFactory<Pair<K,V>,DerivedKeyHashMap<K,V>> factory(KeyFunction<K,V> keyFunction)
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containsKey
public boolean containsKey(@NotNull K key)
Description copied from interface:Map
Returns true if this map contains the specified key.
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put
@NotNull public @NotNull DerivedKeyHashMap<K,V> put(@NotNull K key, V value)
Description copied from interface:Map
Returns a map with the value specified associated to the key specified.If value already exists for the key, it will be replaced.
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get
@Nullable public V get(@NotNull K key)
Description copied from interface:Map
Returns the value associated with the key ornull
if the no value exists with the key specified.
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remove
@NotNull public @NotNull DerivedKeyHashMap<K,V> remove(@NotNull K key)
Description copied from interface:Map
Returns a map with the value associated with the key removed if it exists.
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size
public int size()
Description copied from interface:Traversable
Returns the size of the collection.Warning: infinite collections are possible, as are collections that require traversal to calculate the size.
- Specified by:
size
in interfaceTraversable<K>
- Overrides:
size
in classAbstractTraversable<Pair<K,V>>
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forEach
public <U> void forEach(@NotNull @NotNull Function<Pair<K,V>,U> f)
Description copied from interface:Traversable
All collection methods can be built upon thisforEach
definition.- Specified by:
forEach
in interfaceTraversable<K>
- Overrides:
forEach
in classAbstractIterable<Pair<K,V>>
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