1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.lang3;
18
19 /**
20 * <p>Operations on {@code CharSet} instances.</p>
21 *
22 * <p>This class handles {@code null} input gracefully.
23 * An exception will not be thrown for a {@code null} input.
24 * Each method documents its behaviour in more detail.</p>
25 *
26 * <p>#ThreadSafe#</p>
27 * @see CharSet
28 * @since 1.0
29 * @version $Id: CharSetUtils.java 1436770 2013-01-22 07:09:45Z ggregory $
30 */
31 public class CharSetUtils {
32
33 /**
34 * <p>CharSetUtils instances should NOT be constructed in standard programming.
35 * Instead, the class should be used as {@code CharSetUtils.evaluateSet(null);}.</p>
36 *
37 * <p>This constructor is public to permit tools that require a JavaBean instance
38 * to operate.</p>
39 */
40 public CharSetUtils() {
41 super();
42 }
43
44 // Squeeze
45 //-----------------------------------------------------------------------
46 /**
47 * <p>Squeezes any repetitions of a character that is mentioned in the
48 * supplied set.</p>
49 *
50 * <pre>
51 * CharSetUtils.squeeze(null, *) = null
52 * CharSetUtils.squeeze("", *) = ""
53 * CharSetUtils.squeeze(*, null) = *
54 * CharSetUtils.squeeze(*, "") = *
55 * CharSetUtils.squeeze("hello", "k-p") = "helo"
56 * CharSetUtils.squeeze("hello", "a-e") = "hello"
57 * </pre>
58 *
59 * @see CharSet#getInstance(java.lang.String...) for set-syntax.
60 * @param str the string to squeeze, may be null
61 * @param set the character set to use for manipulation, may be null
62 * @return the modified String, {@code null} if null string input
63 */
64 public static String squeeze(final String str, final String... set) {
65 if (StringUtils.isEmpty(str) || deepEmpty(set)) {
66 return str;
67 }
68 final CharSet chars = CharSet.getInstance(set);
69 final StringBuilder buffer = new StringBuilder(str.length());
70 final char[] chrs = str.toCharArray();
71 final int sz = chrs.length;
72 char lastChar = ' ';
73 char ch = ' ';
74 for (int i = 0; i < sz; i++) {
75 ch = chrs[i];
76 // Compare with contains() last for performance.
77 if (ch == lastChar && i != 0 && chars.contains(ch)) {
78 continue;
79 }
80 buffer.append(ch);
81 lastChar = ch;
82 }
83 return buffer.toString();
84 }
85
86 // Count
87 //-----------------------------------------------------------------------
88 /**
89 * <p>Takes an argument in set-syntax, see evaluateSet,
90 * and returns the number of characters present in the specified string.</p>
91 *
92 * <pre>
93 * CharSetUtils.count(null, *) = 0
94 * CharSetUtils.count("", *) = 0
95 * CharSetUtils.count(*, null) = 0
96 * CharSetUtils.count(*, "") = 0
97 * CharSetUtils.count("hello", "k-p") = 3
98 * CharSetUtils.count("hello", "a-e") = 1
99 * </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(final String str, final String... set) {
107 if (StringUtils.isEmpty(str) || deepEmpty(set)) {
108 return 0;
109 }
110 final CharSet chars = CharSet.getInstance(set);
111 int count = 0;
112 for (final 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(final String str, final String... set) {
142 if (str == null) {
143 return null;
144 }
145 if (str.length() == 0 || deepEmpty(set)) {
146 return StringUtils.EMPTY;
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(final String str, final 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(final String str, final String[] set, final boolean expect) {
188 final CharSet chars = CharSet.getInstance(set);
189 final StringBuilder buffer = new StringBuilder(str.length());
190 final char[] chrs = str.toCharArray();
191 final 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(final String[] strings) {
208 if (strings != null) {
209 for (final String s : strings) {
210 if (StringUtils.isNotEmpty(s)) {
211 return false;
212 }
213 }
214 }
215 return true;
216 }
217 }