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/*
* 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 {
}
}