it.unimi.dsi.fastutil.objects.Object2ObjectMap Maven / Gradle / Ivy
Show all versions of fastutil-core Show documentation
/*
* Copyright (C) 2002-2022 Sebastiano Vigna
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package it.unimi.dsi.fastutil.objects;
import java.util.function.Consumer;
import java.util.Map;
/** A type-specific {@link Map}; provides some additional methods that use polymorphism to avoid (un)boxing, and handling of a default return value.
*
* Besides extending the corresponding type-specific {@linkplain it.unimi.dsi.fastutil.Function function}, this interface strengthens {@link Map#entrySet()},
* {@link #keySet()} and {@link #values()}. Moreover, a number of methods, such as {@link #size()}, {@link #defaultReturnValue()}, etc., are un-defaulted
* as their function default do not make sense for a map.
* Maps returning entry sets of type {@link FastEntrySet} support also fast iteration.
*
*
A submap or subset may or may not have an
* independent default return value (which however must be initialized to the
* default return value of the originator).
*
* @see Map
*/
public interface Object2ObjectMap extends Object2ObjectFunction , Map {
/** An entry set providing fast iteration.
*
* In some cases (e.g., hash-based classes) iteration over an entry set requires the creation
* of a large number of {@link java.util.Map.Entry} objects. Some {@code fastutil}
* maps might return {@linkplain Map#entrySet() entry set} objects of type {@code FastEntrySet}: in this case, {@link #fastIterator() fastIterator()}
* will return an iterator that is guaranteed not to create a large number of objects, possibly
* by returning always the same entry (of course, mutated), and {@link #fastForEach(Consumer)} will apply
* the provided consumer to all elements of the entry set, which might be represented
* always by the same entry (of course, mutated).
*/
interface FastEntrySet extends ObjectSet > {
/** Returns a fast iterator over this entry set; the iterator might return always the same entry instance, suitably mutated.
*
* @return a fast iterator over this entry set; the iterator might return always the same {@link java.util.Map.Entry} instance, suitably mutated.
*/
ObjectIterator > fastIterator();
/** Iterates quickly over this entry set; the iteration might happen always on the same entry instance, suitably mutated.
*
* This default implementation just delegates to {@link #forEach(Consumer)}.
*
* @param consumer a consumer that will by applied to the entries of this set; the entries might be represented
* by the same entry instance, suitably mutated.
* @since 8.1.0
*/
default void fastForEach(final Consumer > consumer) {
forEach(consumer);
}
}
/**
* Returns the number of key/value mappings in this map. If the
* map contains more than {@link Integer#MAX_VALUE} elements, returns {@link Integer#MAX_VALUE}.
*
* @return the number of key-value mappings in this map.
* @see it.unimi.dsi.fastutil.Size64
*/
@Override
int size();
/** Removes all of the mappings from this map (optional operation).
* The map will be empty after this call returns.
*
* @throws UnsupportedOperationException if the {@link #clear()} operation is not supported by this map
*/
@Override
default void clear() { throw new UnsupportedOperationException(); }
/** Sets the default return value (optional operation).
*
* This value must be returned by type-specific versions of {@code get()},
* {@code put()} and {@code remove()} to denote that the map does not contain
* the specified key. It must be {@code null} by default.
*
*
Warning: Changing this to a non-null value can have
* unforeseen consequences. Especially, it breaks compatibility with the
* specifications of Java's {@link java.util.Map} interface. It has to be
* used with great care and thorough study of all method comments is
* recommended.
*
* @param rv the new default return value.
* @see #defaultReturnValue()
*/
@Override
void defaultReturnValue(V rv);
/** Gets the default return value.
*
* @return the current default return value.
*/
@Override
V defaultReturnValue();
/** Returns a type-specific set view of the mappings contained in this map.
*
*
This method is necessary because there is no inheritance along
* type parameters: it is thus impossible to strengthen {@link Map#entrySet()}
* so that it returns an {@link it.unimi.dsi.fastutil.objects.ObjectSet}
* of type-specific entries (the latter makes it possible to
* access keys and values with type-specific methods).
*
* @return a type-specific set view of the mappings contained in this map.
* @see Map#entrySet()
*/
ObjectSet > object2ObjectEntrySet();
/** Returns a set view of the mappings contained in this map.
* @apiNote Note that this specification strengthens the one given in {@link Map#entrySet()}.
*
* @return a set view of the mappings contained in this map.
* @see Map#entrySet()
*/
@Override
@SuppressWarnings({ "unchecked", "rawtypes" })
default ObjectSet> entrySet() {
return (ObjectSet)object2ObjectEntrySet();
}
/** {@inheritDoc}
* This default implementation just delegates to the corresponding function method.
*/
@Override
default V put(final K key, final V value) {
return Object2ObjectFunction.super.put(key, value);
}
/** {@inheritDoc}
*
This default implementation just delegates to the corresponding type-specific–{@linkplain it.unimi.dsi.fastutil.Function function} method.
*/
@Override
default V remove(final Object key) {
return Object2ObjectFunction.super.remove(key);
}
/** {@inheritDoc}
* @apiNote Note that this specification strengthens the one given in {@link Map#keySet()}.
* @return a set view of the keys contained in this map.
* @see Map#keySet()
*/
@Override
ObjectSet keySet();
/** {@inheritDoc}
* @apiNote Note that this specification strengthens the one given in {@link Map#values()}.
* @return a set view of the values contained in this map.
* @see Map#values()
*/
@Override
ObjectCollection values();
/** Returns true if this function contains a mapping for the specified key.
*
* @param key the key.
* @return true if this function associates a value to {@code key}.
* @see Map#containsKey(Object)
*/
@Override
boolean containsKey(Object key);
// Defaultable methods
@Override
default void forEach(final java.util.function.BiConsumer consumer) {
final ObjectSet > entrySet = object2ObjectEntrySet();
final Consumer > wrappingConsumer = (entry) -> consumer.accept((entry.getKey()), (entry.getValue()));
if (entrySet instanceof FastEntrySet) {
((FastEntrySet )entrySet).fastForEach(wrappingConsumer);
} else {
entrySet.forEach(wrappingConsumer);
}
}
/** Returns the value to which the specified key is mapped, or the {@code defaultValue} if this
* map contains no mapping for the key.
*
* @param key the key.
* @param defaultValue the default mapping of the key.
*
* @return the value to which the specified key is mapped, or the {@code defaultValue} if this map contains no mapping for the key.
*
* @see java.util.Map#getOrDefault(Object, Object)
* @since 8.0.0
*/
@Override
default V getOrDefault(final Object key, final V defaultValue) {
final V v;
return ((v = get(key)) != defaultReturnValue() || containsKey(key)) ? v : defaultValue;
}
/** If the specified key is not already associated with a value, associates it with the given
* value and returns the {@linkplain #defaultReturnValue() default return value}, else returns
* the current value.
*
* @param key key with which the specified value is to be associated.
* @param value value to be associated with the specified key.
*
* @return the previous value associated with the specified key, or the {@linkplain #defaultReturnValue() default return value} if there was no mapping for the key.
*
* @see java.util.Map#putIfAbsent(Object, Object)
* @since 8.0.0
*/
default V putIfAbsent(final K key, final V value) {
final V v = get(key), drv = defaultReturnValue();
if (v != drv || containsKey(key)) return v;
put(key, value);
return drv;
}
/** Removes the entry for the specified key only if it is currently mapped to the specified value.
*
* @param key key with which the specified value is associated.
* @param value value expected to be associated with the specified key.
*
* @return {@code true} if the value was removed.
*
* @see java.util.Map#remove(Object, Object)
* @since 8.0.0
*/
default boolean remove(final Object key, final Object value) {
final V curValue = get(key);
if (!java.util.Objects.equals(curValue, value) || (curValue == defaultReturnValue() && !containsKey(key))) return false;
remove(key);
return true;
}
/** Replaces the entry for the specified key only if currently mapped to the specified value.
*
* @param key key with which the specified value is associated.
* @param oldValue value expected to be associated with the specified key.
* @param newValue value to be associated with the specified key.
*
* @return {@code true} if the value was replaced.
*
* @see java.util.Map#replace(Object, Object, Object)
* @since 8.0.0
*/
default boolean replace(final K key, final V oldValue, final V newValue) {
final V curValue = get(key);
if (!java.util.Objects.equals(curValue, oldValue) || (curValue == defaultReturnValue() && !containsKey(key))) return false;
put(key, newValue);
return true;
}
/** Replaces the entry for the specified key only if it is currently mapped to some value.
*
* @param key key with which the specified value is associated.
* @param value value to be associated with the specified key.
*
* @return the previous value associated with the specified key, or the {@linkplain #defaultReturnValue() default return value} if there was no mapping for the key.
*
* @see java.util.Map#replace(Object, Object)
* @since 8.0.0
*/
default V replace(final K key, final V value) { return containsKey(key) ? put(key, value) : defaultReturnValue(); }
/** If the specified key is not already associated with a value, attempts to compute its value
* using the given mapping function and enters it into this map, unless the key is not present
* in the given mapping function.
*
* This version of {@linkplain java.util.Map#computeIfAbsent(Object, java.util.function.Function) computeIfAbsent()}
* uses a type-specific version of {@code fastutil}'s {@link it.unimi.dsi.fastutil.Function Function}.
* Since {@link it.unimi.dsi.fastutil.Function Function} has a {@link it.unimi.dsi.fastutil.Function#containsKey(Object) containsKey()}
* method, it is possible to avoid adding a key by having {@code containsKey()} return {@code false} for that key.
*
* @apiNote all {@code computeIfAbsent()} methods have a different logic based on the argument;
* no delegation is performed, contrarily to other superficially similar
* methods such as {@link java.util.Iterator#forEachRemaining} or {@link java.util.List#replaceAll}.
*
* @param key key with which the specified value is to be associated.
* @param mappingFunction the function to compute a value.
*
* @return the current (existing or computed) value associated with the specified key.
*
* @see java.util.Map#computeIfAbsent(Object, java.util.function.Function)
* @since 8.0.0
*/
default V computeIfAbsent(final K key, final Object2ObjectFunction mappingFunction) {
java.util.Objects.requireNonNull(mappingFunction);
final V v = get(key), drv = defaultReturnValue();
if (v != drv || containsKey(key)) return v;
if (!mappingFunction.containsKey(key)) return drv;
V newValue = mappingFunction.get(key);
put(key, newValue);
return newValue;
}
/**
* @deprecated Please use {@code computeIfAbsent()} instead.
*/
@Deprecated
default V computeObjectIfAbsentPartial(final K key, final Object2ObjectFunction mappingFunction) {
return computeIfAbsent(key, mappingFunction);
}
/** If the value for the specified key is present, attempts to compute a new mapping given the key and its current mapped value.
*
* @apiNote The JDK specification for this method equates not being associated with a value with being associated with {code null}.
* This is not the case for this method.
*
* @param key key with which the specified value is to be associated.
* @param remappingFunction the function to compute a value.
*
* @return the new value associated with the specified key, or the {@linkplain #defaultReturnValue() default return value} if none.
*
* @see java.util.Map#computeIfPresent(Object, java.util.function.BiFunction)
* @since 8.0.0
*/
default V computeIfPresent(final K key, final java.util.function.BiFunction remappingFunction) {
java.util.Objects.requireNonNull(remappingFunction);
final V oldValue = get(key), drv = defaultReturnValue();
if (oldValue == drv && !containsKey(key)) return drv;
final V newValue = remappingFunction.apply((key), (oldValue));
if (newValue == null) { remove(key); return drv; }
put(key, newValue);
return newValue;
}
/** Attempts to compute a mapping for the specified key and its current mapped value (or {@code null} if there is no current mapping).
*
*
If the function returns {@code null}, the mapping is removed (or remains absent if initially absent).
* If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.
*
* @param key key with which the specified value is to be associated.
* @param remappingFunction the function to compute a value.
*
* @return the new value associated with the specified key, or the {@linkplain #defaultReturnValue() default return value} if none.
*
* @see java.util.Map#compute(Object, java.util.function.BiFunction)
* @since 8.0.0
*/
default V compute(final K key, final java.util.function.BiFunction remappingFunction) {
java.util.Objects.requireNonNull(remappingFunction);
final V oldValue = get(key), drv = defaultReturnValue();
final boolean contained = oldValue != drv || containsKey(key);
final V newValue = remappingFunction.apply((key), contained ? (oldValue) : null);
if (newValue == null) {
if (contained) remove(key);
return drv;
}
put(key, newValue);
return newValue;
}
/**
* If the specified key is not already associated with a value, associates it with the given {@code value}.
* Otherwise, replaces the associated value with the results of the given remapping function, or removes if the result is {@code null}.
*
* @apiNote The JDK specification for this method equates not being associated with a value with being associated with {code null}.
* This is not the case for this method.
*
* @param key key with which the resulting value is to be associated.
* @param value the value to be merged with the existing value associated with the key or, if no existing value is associated with the key, to be associated with the key.
* @param remappingFunction the function to recompute a value if present.
*
* @return the new value associated with the specified key, or the {@linkplain #defaultReturnValue() default return value} if no value is associated with the key.
*
* @see java.util.Map#merge(Object, Object, java.util.function.BiFunction)
* @since 8.0.0
*/
default V merge(final K key, final V value, final java.util.function.BiFunction remappingFunction) {
java.util.Objects.requireNonNull(remappingFunction);
java.util.Objects.requireNonNull(value);
final V oldValue = get(key), drv = defaultReturnValue();
final V newValue;
if (oldValue != drv || containsKey(key)) {
final V mergedValue = remappingFunction.apply((oldValue), (value));
if (mergedValue == null) { remove(key); return drv; }
newValue = (mergedValue);
} else {
newValue = value;
}
put(key, newValue);
return newValue;
}
/** A type-specific {@link java.util.Map.Entry}; provides some additional methods
* that use polymorphism to avoid (un)boxing.
*
* @see java.util.Map.Entry
*/
interface Entry extends Map.Entry {
}
}