001/*
002 * Copyright (C) 2009 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.collect.testing;
018
019import static java.util.Arrays.asList;
020
021import com.google.common.annotations.GwtCompatible;
022import java.util.ArrayList;
023import java.util.Collection;
024import java.util.List;
025import java.util.Set;
026import org.jspecify.annotations.NonNull;
027import org.jspecify.annotations.NullMarked;
028import org.jspecify.annotations.Nullable;
029
030/**
031 * A simplistic set which implements the bare minimum so that it can be used in tests without
032 * relying on any specific Set implementations. Slow. Explicitly allows null elements so that they
033 * can be used in the testers.
034 *
035 * @author Regina O'Dell
036 */
037@GwtCompatible
038@NullMarked
039public final class MinimalSet<E extends @Nullable Object> extends MinimalCollection<E>
040    implements Set<E> {
041
042  @SuppressWarnings("unchecked") // empty Object[] as E[]
043  public static <E extends @Nullable Object> MinimalSet<E> of(E... contents) {
044    return ofClassAndContents(Object.class, (E[]) new Object[0], asList(contents));
045  }
046
047  @SuppressWarnings("unchecked") // empty Object[] as E[]
048  public static <E extends @Nullable Object> MinimalSet<E> from(Collection<? extends E> contents) {
049    return ofClassAndContents(Object.class, (E[]) new Object[0], contents);
050  }
051
052  public static <E extends @Nullable Object> MinimalSet<E> ofClassAndContents(
053      Class<? super @NonNull E> type, E[] emptyArrayForContents, Iterable<? extends E> contents) {
054    List<E> setContents = new ArrayList<>();
055    for (E e : contents) {
056      if (!setContents.contains(e)) {
057        setContents.add(e);
058      }
059    }
060    return new MinimalSet<>(type, setContents.toArray(emptyArrayForContents));
061  }
062
063  private MinimalSet(Class<? super @NonNull E> type, E... contents) {
064    super(type, true, contents);
065  }
066
067  /*
068   * equals() and hashCode() are more specific in the Set contract.
069   */
070
071  @Override
072  public boolean equals(@Nullable Object object) {
073    if (object instanceof Set) {
074      Set<?> that = (Set<?>) object;
075      return (this.size() == that.size()) && this.containsAll(that);
076    }
077    return false;
078  }
079
080  @Override
081  public int hashCode() {
082    int hashCodeSum = 0;
083    for (Object o : this) {
084      hashCodeSum += (o == null) ? 0 : o.hashCode();
085    }
086    return hashCodeSum;
087  }
088}