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1   /*
2    * Copyright (C) 2009 The Guava Authors
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    * http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package com.google.common.collect.testing;
18  
19  import com.google.common.annotations.GwtCompatible;
20  import java.util.ArrayList;
21  import java.util.Arrays;
22  import java.util.Collection;
23  import java.util.List;
24  import java.util.Set;
25  
26  /**
27   * A simplistic set which implements the bare minimum so that it can be used in
28   * tests without relying on any specific Set implementations. Slow. Explicitly
29   * allows null elements so that they can be used in the testers.
30   *
31   * @author Regina O'Dell
32   */
33  @GwtCompatible
34  public class MinimalSet<E> extends MinimalCollection<E> implements Set<E> {
35  
36    @SuppressWarnings("unchecked") // empty Object[] as E[]
37    public static <E> MinimalSet<E> of(E... contents) {
38      return ofClassAndContents(Object.class, (E[]) new Object[0], Arrays.asList(contents));
39    }
40  
41    @SuppressWarnings("unchecked") // empty Object[] as E[]
42    public static <E> MinimalSet<E> from(Collection<? extends E> contents) {
43      return ofClassAndContents(Object.class, (E[]) new Object[0], contents);
44    }
45  
46    public static <E> MinimalSet<E> ofClassAndContents(
47        Class<? super E> type, E[] emptyArrayForContents, Iterable<? extends E> contents) {
48      List<E> setContents = new ArrayList<E>();
49      for (E e : contents) {
50        if (!setContents.contains(e)) {
51          setContents.add(e);
52        }
53      }
54      return new MinimalSet<E>(type, setContents.toArray(emptyArrayForContents));
55    }
56  
57    private MinimalSet(Class<? super E> type, E... contents) {
58      super(type, true, contents);
59    }
60  
61    /*
62     * equals() and hashCode() are more specific in the Set contract.
63     */
64  
65    @Override
66    public boolean equals(Object object) {
67      if (object instanceof Set) {
68        Set<?> that = (Set<?>) object;
69        return (this.size() == that.size()) && this.containsAll(that);
70      }
71      return false;
72    }
73  
74    @Override
75    public int hashCode() {
76      int hashCodeSum = 0;
77      for (Object o : this) {
78        hashCodeSum += (o == null) ? 0 : o.hashCode();
79      }
80      return hashCodeSum;
81    }
82  }