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 class MinimalSet<E extends @Nullable Object> extends MinimalCollection<E> implements Set<E> {
040
041  @SuppressWarnings("unchecked") // empty Object[] as E[]
042  public static <E extends @Nullable Object> MinimalSet<E> of(E... contents) {
043    return ofClassAndContents(Object.class, (E[]) new Object[0], asList(contents));
044  }
045
046  @SuppressWarnings("unchecked") // empty Object[] as E[]
047  public static <E extends @Nullable Object> MinimalSet<E> from(Collection<? extends E> contents) {
048    return ofClassAndContents(Object.class, (E[]) new Object[0], contents);
049  }
050
051  public static <E extends @Nullable Object> MinimalSet<E> ofClassAndContents(
052      Class<? super @NonNull E> type, E[] emptyArrayForContents, Iterable<? extends E> contents) {
053    List<E> setContents = new ArrayList<>();
054    for (E e : contents) {
055      if (!setContents.contains(e)) {
056        setContents.add(e);
057      }
058    }
059    return new MinimalSet<>(type, setContents.toArray(emptyArrayForContents));
060  }
061
062  private MinimalSet(Class<? super @NonNull E> type, E... contents) {
063    super(type, true, contents);
064  }
065
066  /*
067   * equals() and hashCode() are more specific in the Set contract.
068   */
069
070  @Override
071  public boolean equals(@Nullable Object object) {
072    if (object instanceof Set) {
073      Set<?> that = (Set<?>) object;
074      return (this.size() == that.size()) && this.containsAll(that);
075    }
076    return false;
077  }
078
079  @Override
080  public int hashCode() {
081    int hashCodeSum = 0;
082    for (Object o : this) {
083      hashCodeSum += (o == null) ? 0 : o.hashCode();
084    }
085    return hashCodeSum;
086  }
087}