001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.lang3;
018
019 /**
020 * <p>Operations on {@code CharSet} instances.</p>
021 *
022 * <p>This class handles {@code null} input gracefully.
023 * An exception will not be thrown for a {@code null} input.
024 * Each method documents its behaviour in more detail.</p>
025 *
026 * <p>#ThreadSafe#</p>
027 * @see CharSet
028 * @since 1.0
029 * @version $Id: CharSetUtils.java 1144916 2011-07-10 17:50:21Z ggregory $
030 */
031 public class CharSetUtils {
032
033 /**
034 * <p>CharSetUtils instances should NOT be constructed in standard programming.
035 * Instead, the class should be used as {@code CharSetUtils.evaluateSet(null);}.</p>
036 *
037 * <p>This constructor is public to permit tools that require a JavaBean instance
038 * to operate.</p>
039 */
040 public CharSetUtils() {
041 super();
042 }
043
044 // Squeeze
045 //-----------------------------------------------------------------------
046 /**
047 * <p>Squeezes any repetitions of a character that is mentioned in the
048 * supplied set.</p>
049 *
050 * <pre>
051 * CharSetUtils.squeeze(null, *) = null
052 * CharSetUtils.squeeze("", *) = ""
053 * CharSetUtils.squeeze(*, null) = *
054 * CharSetUtils.squeeze(*, "") = *
055 * CharSetUtils.squeeze("hello", "k-p") = "helo"
056 * CharSetUtils.squeeze("hello", "a-e") = "hello"
057 * </pre>
058 *
059 * @see CharSet#getInstance(java.lang.String...) for set-syntax.
060 * @param str the string to squeeze, may be null
061 * @param set the character set to use for manipulation, may be null
062 * @return the modified String, {@code null} if null string input
063 */
064 public static String squeeze(String str, String... set) {
065 if (StringUtils.isEmpty(str) || deepEmpty(set)) {
066 return str;
067 }
068 CharSet chars = CharSet.getInstance(set);
069 StringBuilder buffer = new StringBuilder(str.length());
070 char[] chrs = str.toCharArray();
071 int sz = chrs.length;
072 char lastChar = ' ';
073 char ch = ' ';
074 for (int i = 0; i < sz; i++) {
075 ch = chrs[i];
076 // Compare with contains() last for performance.
077 if (ch == lastChar && i != 0 && chars.contains(ch)) {
078 continue;
079 }
080 buffer.append(ch);
081 lastChar = ch;
082 }
083 return buffer.toString();
084 }
085
086 // Count
087 //-----------------------------------------------------------------------
088 /**
089 * <p>Takes an argument in set-syntax, see evaluateSet,
090 * and returns the number of characters present in the specified string.</p>
091 *
092 * <pre>
093 * CharSetUtils.count(null, *) = 0
094 * CharSetUtils.count("", *) = 0
095 * CharSetUtils.count(*, null) = 0
096 * CharSetUtils.count(*, "") = 0
097 * CharSetUtils.count("hello", "k-p") = 3
098 * CharSetUtils.count("hello", "a-e") = 1
099 * </pre>
100 *
101 * @see CharSet#getInstance(java.lang.String...) for set-syntax.
102 * @param str String to count characters in, may be null
103 * @param set String[] set of characters to count, may be null
104 * @return the character count, zero if null string input
105 */
106 public static int count(String str, String... set) {
107 if (StringUtils.isEmpty(str) || deepEmpty(set)) {
108 return 0;
109 }
110 CharSet chars = CharSet.getInstance(set);
111 int count = 0;
112 for (char c : str.toCharArray()) {
113 if (chars.contains(c)) {
114 count++;
115 }
116 }
117 return count;
118 }
119
120 // Keep
121 //-----------------------------------------------------------------------
122 /**
123 * <p>Takes an argument in set-syntax, see evaluateSet,
124 * and keeps any of characters present in the specified string.</p>
125 *
126 * <pre>
127 * CharSetUtils.keep(null, *) = null
128 * CharSetUtils.keep("", *) = ""
129 * CharSetUtils.keep(*, null) = ""
130 * CharSetUtils.keep(*, "") = ""
131 * CharSetUtils.keep("hello", "hl") = "hll"
132 * CharSetUtils.keep("hello", "le") = "ell"
133 * </pre>
134 *
135 * @see CharSet#getInstance(java.lang.String...) for set-syntax.
136 * @param str String to keep characters from, may be null
137 * @param set String[] set of characters to keep, may be null
138 * @return the modified String, {@code null} if null string input
139 * @since 2.0
140 */
141 public static String keep(String str, String... set) {
142 if (str == null) {
143 return null;
144 }
145 if (str.length() == 0 || deepEmpty(set)) {
146 return "";
147 }
148 return modify(str, set, true);
149 }
150
151 // Delete
152 //-----------------------------------------------------------------------
153 /**
154 * <p>Takes an argument in set-syntax, see evaluateSet,
155 * and deletes any of characters present in the specified string.</p>
156 *
157 * <pre>
158 * CharSetUtils.delete(null, *) = null
159 * CharSetUtils.delete("", *) = ""
160 * CharSetUtils.delete(*, null) = *
161 * CharSetUtils.delete(*, "") = *
162 * CharSetUtils.delete("hello", "hl") = "eo"
163 * CharSetUtils.delete("hello", "le") = "ho"
164 * </pre>
165 *
166 * @see CharSet#getInstance(java.lang.String...) for set-syntax.
167 * @param str String to delete characters from, may be null
168 * @param set String[] set of characters to delete, may be null
169 * @return the modified String, {@code null} if null string input
170 */
171 public static String delete(String str, String... set) {
172 if (StringUtils.isEmpty(str) || deepEmpty(set)) {
173 return str;
174 }
175 return modify(str, set, false);
176 }
177
178 //-----------------------------------------------------------------------
179 /**
180 * Implementation of delete and keep
181 *
182 * @param str String to modify characters within
183 * @param set String[] set of characters to modify
184 * @param expect whether to evaluate on match, or non-match
185 * @return the modified String, not null
186 */
187 private static String modify(String str, String[] set, boolean expect) {
188 CharSet chars = CharSet.getInstance(set);
189 StringBuilder buffer = new StringBuilder(str.length());
190 char[] chrs = str.toCharArray();
191 int sz = chrs.length;
192 for(int i=0; i<sz; i++) {
193 if(chars.contains(chrs[i]) == expect) {
194 buffer.append(chrs[i]);
195 }
196 }
197 return buffer.toString();
198 }
199
200 /**
201 * Determines whether or not all the Strings in an array are
202 * empty or not.
203 *
204 * @param strings String[] whose elements are being checked for emptiness
205 * @return whether or not the String is empty
206 */
207 private static boolean deepEmpty(String[] strings) {
208 if (strings != null) {
209 for (String s : strings) {
210 if (StringUtils.isNotEmpty(s)) {
211 return false;
212 }
213 }
214 }
215 return true;
216 }
217 }