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      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      */
     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      */
     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
     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
     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 
    116     private StringUtil() {
    117     }
    118 }
    119