1 /*
2  * Copyright (C) 2012 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 
17 package com.android.inputmethod.latin.common;
18 
19 import com.android.inputmethod.annotations.UsedForTesting;
20 
21 import java.util.ArrayList;
22 import java.util.Collection;
23 import java.util.Map;
24 
25 import javax.annotation.Nonnull;
26 import javax.annotation.Nullable;
27 
28 /**
29  * Utility methods for working with collections.
30  */
31 public final class CollectionUtils {
CollectionUtils()32     private CollectionUtils() {
33         // This utility class is not publicly instantiable.
34     }
35 
36     /**
37      * Converts a sub-range of the given array to an ArrayList of the appropriate type.
38      * @param array Array to be converted.
39      * @param start First index inclusive to be converted.
40      * @param end Last index exclusive to be converted.
41      * @throws IllegalArgumentException if start or end are out of range or start > end.
42      */
43     @Nonnull
arrayAsList(@onnull final E[] array, final int start, final int end)44     public static <E> ArrayList<E> arrayAsList(@Nonnull final E[] array, final int start,
45             final int end) {
46         if (start < 0 || start > end || end > array.length) {
47             throw new IllegalArgumentException("Invalid start: " + start + " end: " + end
48                     + " with array.length: " + array.length);
49         }
50 
51         final ArrayList<E> list = new ArrayList<>(end - start);
52         for (int i = start; i < end; i++) {
53             list.add(array[i]);
54         }
55         return list;
56     }
57 
58     /**
59      * Tests whether c contains no elements, true if c is null or c is empty.
60      * @param c Collection to test.
61      * @return Whether c contains no elements.
62      */
63     @UsedForTesting
isNullOrEmpty(@ullable final Collection c)64     public static boolean isNullOrEmpty(@Nullable final Collection c) {
65         return c == null || c.isEmpty();
66     }
67 
68     /**
69      * Tests whether map contains no elements, true if map is null or map is empty.
70      * @param map Map to test.
71      * @return Whether map contains no elements.
72      */
73     @UsedForTesting
isNullOrEmpty(@ullable final Map map)74     public static boolean isNullOrEmpty(@Nullable final Map map) {
75         return map == null || map.isEmpty();
76     }
77 }
78