1 /*
2  * Copyright (C) 2016 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 androidx.room.util;
18 
19 import android.util.Log;
20 
21 import androidx.annotation.Nullable;
22 import androidx.annotation.RestrictTo;
23 
24 import java.util.ArrayList;
25 import java.util.List;
26 import java.util.StringTokenizer;
27 
28 /**
29  * @hide
30  *
31  * String utilities for Room
32  */
33 @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
34 public class StringUtil {
35 
36     @SuppressWarnings("unused")
37     public static final String[] EMPTY_STRING_ARRAY = new String[0];
38     /**
39      * Returns a new StringBuilder to be used while producing SQL queries.
40      *
41      * @return A new or recycled StringBuilder
42      */
newStringBuilder()43     public static StringBuilder newStringBuilder() {
44         // TODO pool:
45         return new StringBuilder();
46     }
47 
48     /**
49      * Adds bind variable placeholders (?) to the given string. Each placeholder is separated
50      * by a comma.
51      *
52      * @param builder The StringBuilder for the query
53      * @param count Number of placeholders
54      */
appendPlaceholders(StringBuilder builder, int count)55     public static void appendPlaceholders(StringBuilder builder, int count) {
56         for (int i = 0; i < count; i++) {
57             builder.append("?");
58             if (i < count - 1) {
59                 builder.append(",");
60             }
61         }
62     }
63     /**
64      * Splits a comma separated list of integers to integer list.
65      * <p>
66      * If an input is malformed, it is omitted from the result.
67      *
68      * @param input Comma separated list of integers.
69      * @return A List containing the integers or null if the input is null.
70      */
71     @Nullable
splitToIntList(@ullable String input)72     public static List<Integer> splitToIntList(@Nullable String input) {
73         if (input == null) {
74             return null;
75         }
76         List<Integer> result = new ArrayList<>();
77         StringTokenizer tokenizer = new StringTokenizer(input, ",");
78         while (tokenizer.hasMoreElements()) {
79             final String item = tokenizer.nextToken();
80             try {
81                 result.add(Integer.parseInt(item));
82             } catch (NumberFormatException ex) {
83                 Log.e("ROOM", "Malformed integer list", ex);
84             }
85         }
86         return result;
87     }
88 
89     /**
90      * Joins the given list of integers into a comma separated list.
91      *
92      * @param input The list of integers.
93      * @return Comma separated string composed of integers in the list. If the list is null, return
94      * value is null.
95      */
96     @Nullable
joinIntoString(@ullable List<Integer> input)97     public static String joinIntoString(@Nullable List<Integer> input) {
98         if (input == null) {
99             return null;
100         }
101 
102         final int size = input.size();
103         if (size == 0) {
104             return "";
105         }
106         StringBuilder sb = new StringBuilder();
107         for (int i = 0; i < size; i++) {
108             sb.append(Integer.toString(input.get(i)));
109             if (i < size - 1) {
110                 sb.append(",");
111             }
112         }
113         return sb.toString();
114     }
115 
StringUtil()116     private StringUtil() {
117     }
118 }
119