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/*
* Copyright (C) 2002-2023 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.Spliterator;
import java.util.Set;
import static it.unimi.dsi.fastutil.Size64.sizeOf;
/**
* A type-specific {@link Set}; provides some additional methods that use polymorphism to avoid
* (un)boxing.
*
*
* Additionally, this interface strengthens (again) {@link #iterator()}.
*
* @see Set
*/
public interface ObjectSet extends ObjectCollection, Set {
/**
* Returns a type-specific iterator on the elements of this set.
*
* @apiNote This specification strengthens the one given in {@link java.lang.Iterable#iterator()},
* which was already strengthened in the corresponding type-specific class, but was
* weakened by the fact that this interface extends {@link Set}.
*
* Also, this is generally the only {@code iterator} method subclasses should override.
*
* @return a type-specific iterator on the elements of this set.
*/
@Override
ObjectIterator iterator();
/**
* Returns a type-specific spliterator on the elements of this set.
*
*
* Set spliterators must report at least {@link Spliterator#DISTINCT}.
*
*
* See {@link java.util.Set#spliterator()} for more documentation on the requirements of the
* returned spliterator.
*
* @apiNote This specification strengthens the one given in
* {@link java.util.Collection#spliterator()}, which was already strengthened in the
* corresponding type-specific class, but was weakened by the fact that this interface
* extends {@link Set}.
*
* Also, this is generally the only {@code spliterator} method subclasses should override.
*
* @implSpec The default implementation returns a late-binding spliterator (see {@link Spliterator}
* for documentation on what binding policies mean) that wraps this instance's type
* specific {@link #iterator}.
*
* Additionally, it reports {@link Spliterator#SIZED} and {@link Spliterator#DISTINCT}.
*
* @implNote As this default implementation wraps the iterator, and {@link java.util.Iterator} is an
* inherently linear API, the returned spliterator will yield limited performance gains
* when run in parallel contexts, as the returned spliterator's
* {@link Spliterator#trySplit() trySplit()} will have linear runtime.
*
* @return {@inheritDoc}
* @since 8.5.0
*/
@Override
default ObjectSpliterator spliterator() {
return ObjectSpliterators.asSpliterator(iterator(), sizeOf(this), ObjectSpliterators.SET_SPLITERATOR_CHARACTERISTICS);
}
/**
* Returns an immutable empty set.
*
* @return an immutable empty set.
*/
@SuppressWarnings("unchecked")
public static ObjectSet of() {
return ObjectSets.UNMODIFIABLE_EMPTY_SET;
}
/**
* Returns an immutable set with the element given.
*
* @param e an element.
* @return an immutable set containing {@code e}.
*/
public static ObjectSet of(K e) {
return ObjectSets.singleton(e);
}
/**
* Returns an immutable set with the elements given.
*
* @param e0 the first element.
* @param e1 the second element.
* @return an immutable set containing {@code e0} and {@code e1}.
* @throws IllegalArgumentException if there were duplicate entries.
*/
public static ObjectSet of(K e0, K e1) {
ObjectArraySet innerSet = new ObjectArraySet<>(2);
innerSet.add(e0);
if (!innerSet.add(e1)) {
throw new IllegalArgumentException("Duplicate element: " + e1);
}
return ObjectSets.unmodifiable(innerSet);
}
/**
* Returns an immutable set with the elements given.
*
* @param e0 the first element.
* @param e1 the second element.
* @param e2 the third element.
* @return an immutable set containing {@code e0}, {@code e1}, and {@code e2}.
* @throws IllegalArgumentException if there were duplicate entries.
*/
public static ObjectSet of(K e0, K e1, K e2) {
ObjectArraySet innerSet = new ObjectArraySet<>(3);
innerSet.add(e0);
if (!innerSet.add(e1)) {
throw new IllegalArgumentException("Duplicate element: " + e1);
}
if (!innerSet.add(e2)) {
throw new IllegalArgumentException("Duplicate element: " + e2);
}
return ObjectSets.unmodifiable(innerSet);
}
/**
* Returns an immutable list with the elements given.
*
* @param a the list of elements that will be in the final set.
* @return an immutable set containing the elements in {@code a}.
* @throws IllegalArgumentException if there are any duplicate entries.
*/
@SafeVarargs
public static ObjectSet of(K... a) {
switch (a.length) {
case 0:
return of();
case 1:
return of(a[0]);
case 2:
return of(a[0], a[1]);
case 3:
return of(a[0], a[1], a[2]);
default:
// fall through
}
// Will copy, but that is the only way we assure immutability.
ObjectSet innerSet = a.length <= ObjectSets.ARRAY_SET_CUTOFF ? new ObjectArraySet<>(a.length) : new ObjectOpenHashSet<>(a.length);
for (K element : a) {
if (!innerSet.add(element)) {
throw new IllegalArgumentException("Duplicate element: " + element);
}
}
return ObjectSets.unmodifiable(innerSet);
}
}