1/*
2 * Copyright (C) 2007 The Android Open Source Project
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
17package com.google.android.collect;
18
19import android.util.ArraySet;
20
21import java.util.Collections;
22import java.util.EnumSet;
23import java.util.HashSet;
24import java.util.SortedSet;
25import java.util.TreeSet;
26
27/**
28 * Provides static methods for creating mutable {@code Set} instances easily and
29 * other static methods for working with Sets.
30 *
31 */
32public class Sets {
33
34    /**
35     * Creates an empty {@code HashSet} instance.
36     *
37     * <p><b>Note:</b> if {@code E} is an {@link Enum} type, use {@link
38     * EnumSet#noneOf} instead.
39     *
40     * <p><b>Note:</b> if you only need an <i>immutable</i> empty Set,
41     * use {@link Collections#emptySet} instead.
42     *
43     * @return a newly-created, initially-empty {@code HashSet}
44     */
45    public static <K> HashSet<K> newHashSet() {
46        return new HashSet<K>();
47    }
48
49    /**
50     * Creates a {@code HashSet} instance containing the given elements.
51     *
52     * <p><b>Note:</b> due to a bug in javac 1.5.0_06, we cannot support the
53     * following:
54     *
55     * <p>{@code Set<Base> set = Sets.newHashSet(sub1, sub2);}
56     *
57     * <p>where {@code sub1} and {@code sub2} are references to subtypes of {@code
58     * Base}, not of {@code Base} itself. To get around this, you must use:
59     *
60     * <p>{@code Set<Base> set = Sets.<Base>newHashSet(sub1, sub2);}
61     *
62     * @param elements the elements that the set should contain
63     * @return a newly-created {@code HashSet} containing those elements (minus
64     *     duplicates)
65     */
66    public static <E> HashSet<E> newHashSet(E... elements) {
67        int capacity = elements.length * 4 / 3 + 1;
68        HashSet<E> set = new HashSet<E>(capacity);
69        Collections.addAll(set, elements);
70        return set;
71    }
72
73    /**
74     * Creates an empty {@code SortedSet} instance.
75     *
76     * @return a newly-created, initially-empty {@code SortedSet}.
77     */
78    public static <E> SortedSet<E> newSortedSet() {
79        return new TreeSet<E>();
80    }
81
82    /**
83     * Creates a {@code SortedSet} instance containing the given elements.
84     *
85     * @param elements the elements that the set should contain
86     * @return a newly-created {@code SortedSet} containing those elements (minus
87     *     duplicates)
88     */
89    public static <E> SortedSet<E> newSortedSet(E... elements) {
90        SortedSet<E> set = new TreeSet<E>();
91        Collections.addAll(set, elements);
92        return set;
93    }
94
95    /**
96     * Creates a {@code ArraySet} instance.
97     */
98    public static <E> ArraySet<E> newArraySet() {
99        return new ArraySet<E>();
100    }
101
102    /**
103     * Creates a {@code ArraySet} instance containing the given elements.
104     */
105    public static <E> ArraySet<E> newArraySet(E... elements) {
106        int capacity = elements.length * 4 / 3 + 1;
107        ArraySet<E> set = new ArraySet<E>(capacity);
108        Collections.addAll(set, elements);
109        return set;
110    }
111}
112