1/*
2 * Copyright (C) 2017 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.android.server.backup.utils;
18
19import android.util.SparseArray;
20
21import java.util.HashSet;
22
23/**
24 * Helper functions for manipulating instances of {@link SparseArray}.
25 */
26public final class SparseArrayUtils {
27    // Statics only
28    private SparseArrayUtils() {}
29
30    /**
31     * Given a {@link SparseArray<HashSet>}, returns a new {@link HashSet} containing every element
32     * from every set in the array.
33     *
34     * @param sets The array of sets from which to take the union.
35     * @param <V> The type of element contained in the set.
36     * @return The complete set.
37     */
38    public static<V> HashSet<V> union(SparseArray<HashSet<V>> sets) {
39        HashSet<V> unionSet = new HashSet<>();
40        int n = sets.size();
41        for (int i = 0; i < n; i++) {
42            HashSet<V> ithSet = sets.valueAt(i);
43            if (ithSet != null) {
44                unionSet.addAll(ithSet);
45            }
46        }
47        return unionSet;
48    }
49}
50