    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.lang;
    018
    019    /**
    020     * <p>Operations on char primitives and Character objects.</p>
    021     *
    022     * <p>This class tries to handle <code>null</code> input gracefully.
    023     * An exception will not be thrown for a <code>null</code> input.
    024     * Each method documents its behaviour in more detail.</p>
    025     *
    026     * @author Apache Software Foundation
    027     * @since 2.1
    028     * @version $Id: CharUtils.java 905636 2010-02-02 14:03:32Z niallp $
    029     */
    030    public class CharUtils {
    031
    032        private static final String CHAR_STRING =
    033            "\u0000\u0001\u0002\u0003\u0004\u0005\u0006\u0007" +
    034            "\b\t\n\u000b\f\r\u000e\u000f" +
    035            "\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017" +
    036            "\u0018\u0019\u001a\u001b\u001c\u001d\u001e\u001f" +
    037            "\u0020\u0021\"\u0023\u0024\u0025\u0026\u0027" +
    038            "\u0028\u0029\u002a\u002b\u002c\u002d\u002e\u002f" +
    039            "\u0030\u0031\u0032\u0033\u0034\u0035\u0036\u0037" +
    040            "\u0038\u0039\u003a\u003b\u003c\u003d\u003e\u003f" +
    041            "\u0040\u0041\u0042\u0043\u0044\u0045\u0046\u0047" +
    042            "\u0048\u0049\u004a\u004b\u004c\u004d\u004e\u004f" +
    043            "\u0050\u0051\u0052\u0053\u0054\u0055\u0056\u0057" +
    044            "\u0058\u0059\u005a\u005b\\\u005d\u005e\u005f" +
    045            "\u0060\u0061\u0062\u0063\u0064\u0065\u0066\u0067" +
    046            "\u0068\u0069\u006a\u006b\u006c\u006d\u006e\u006f" +
    047            "\u0070\u0071\u0072\u0073\u0074\u0075\u0076\u0077" +
    048            "\u0078\u0079\u007a\u007b\u007c\u007d\u007e\u007f";
    049
    050        private static final String[] CHAR_STRING_ARRAY = new String[128];
    051        private static final Character[] CHAR_ARRAY = new Character[128];
    052
    053        /**
    054         * <code>\u000a</code> linefeed LF ('\n').
    055         *
    056         * @see <a href="http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#101089">JLF: Escape Sequences
    057         *      for Character and String Literals</a>
    058         * @since 2.2
    059         */
    060        public static final char LF = '\n';
    061
    062        /**
    063         * <code>\u000d</code> carriage return CR ('\r').
    064         *
    065         * @see <a href="http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#101089">JLF: Escape Sequences
    066         *      for Character and String Literals</a>
    067         * @since 2.2
    068         */
    069        public static final char CR = '\r';
    070
    071
    072        static {
    073            for (int i = 127; i >= 0; i--) {
    074                CHAR_STRING_ARRAY[i] = CHAR_STRING.substring(i, i + 1);
    075                CHAR_ARRAY[i] = new Character((char) i);
    076            }
    077        }
    078
    079        /**
    080         * <p><code>CharUtils</code> instances should NOT be constructed in standard programming.
    081         * Instead, the class should be used as <code>CharUtils.toString('c');</code>.</p>
    082         *
    083         * <p>This constructor is public to permit tools that require a JavaBean instance
    084         * to operate.</p>
    085         */
    086        public CharUtils() {
    087          super();
    088        }
    089
    090        //-----------------------------------------------------------------------
    091        /**
    092         * <p>Converts the character to a Character.</p>
    093         *
    094         * <p>For ASCII 7 bit characters, this uses a cache that will return the
    095         * same Character object each time.</p>
    096         *
    097         * <pre>
    098         *   CharUtils.toCharacterObject(' ')  = ' '
    099         *   CharUtils.toCharacterObject('A')  = 'A'
    100         * </pre>
    101         *
    102         * @param ch  the character to convert
    103         * @return a Character of the specified character
    104         */
    105        public static Character toCharacterObject(char ch) {
    106            if (ch < CHAR_ARRAY.length) {
    107                return CHAR_ARRAY[ch];
    108            }
    109            return new Character(ch);
    110        }
    111
    112        /**
    113         * <p>Converts the String to a Character using the first character, returning
    114         * null for empty Strings.</p>
    115         *
    116         * <p>For ASCII 7 bit characters, this uses a cache that will return the
    117         * same Character object each time.</p>
    118         *
    119         * <pre>
    120         *   CharUtils.toCharacterObject(null) = null
    121         *   CharUtils.toCharacterObject("")   = null
    122         *   CharUtils.toCharacterObject("A")  = 'A'
    123         *   CharUtils.toCharacterObject("BA") = 'B'
    124         * </pre>
    125         *
    126         * @param str  the character to convert
    127         * @return the Character value of the first letter of the String
    128         */
    129        public static Character toCharacterObject(String str) {
    130            if (StringUtils.isEmpty(str)) {
    131                return null;
    132            }
    133            return toCharacterObject(str.charAt(0));
    134        }
    135
    136        //-----------------------------------------------------------------------
    137        /**
    138         * <p>Converts the Character to a char throwing an exception for <code>null</code>.</p>
    139         *
    140         * <pre>
    141         *   CharUtils.toChar(null) = IllegalArgumentException
    142         *   CharUtils.toChar(' ')  = ' '
    143         *   CharUtils.toChar('A')  = 'A'
    144         * </pre>
    145         *
    146         * @param ch  the character to convert
    147         * @return the char value of the Character
    148         * @throws IllegalArgumentException if the Character is null
    149         */
    150        public static char toChar(Character ch) {
    151            if (ch == null) {
    152                throw new IllegalArgumentException("The Character must not be null");
    153            }
    154            return ch.charValue();
    155        }
    156
    157        /**
    158         * <p>Converts the Character to a char handling <code>null</code>.</p>
    159         *
    160         * <pre>
    161         *   CharUtils.toChar(null, 'X') = 'X'
    162         *   CharUtils.toChar(' ', 'X')  = ' '
    163         *   CharUtils.toChar('A', 'X')  = 'A'
    164         * </pre>
    165         *
    166         * @param ch  the character to convert
    167         * @param defaultValue  the value to use if the  Character is null
    168         * @return the char value of the Character or the default if null
    169         */
    170        public static char toChar(Character ch, char defaultValue) {
    171            if (ch == null) {
    172                return defaultValue;
    173            }
    174            return ch.charValue();
    175        }
    176
    177        //-----------------------------------------------------------------------
    178        /**
    179         * <p>Converts the String to a char using the first character, throwing
    180         * an exception on empty Strings.</p>
    181         *
    182         * <pre>
    183         *   CharUtils.toChar(null) = IllegalArgumentException
    184         *   CharUtils.toChar("")   = IllegalArgumentException
    185         *   CharUtils.toChar("A")  = 'A'
    186         *   CharUtils.toChar("BA") = 'B'
    187         * </pre>
    188         *
    189         * @param str  the character to convert
    190         * @return the char value of the first letter of the String
    191         * @throws IllegalArgumentException if the String is empty
    192         */
    193        public static char toChar(String str) {
    194            if (StringUtils.isEmpty(str)) {
    195                throw new IllegalArgumentException("The String must not be empty");
    196            }
    197            return str.charAt(0);
    198        }
    199
    200        /**
    201         * <p>Converts the String to a char using the first character, defaulting
    202         * the value on empty Strings.</p>
    203         *
    204         * <pre>
    205         *   CharUtils.toChar(null, 'X') = 'X'
    206         *   CharUtils.toChar("", 'X')   = 'X'
    207         *   CharUtils.toChar("A", 'X')  = 'A'
    208         *   CharUtils.toChar("BA", 'X') = 'B'
    209         * </pre>
    210         *
    211         * @param str  the character to convert
    212         * @param defaultValue  the value to use if the  Character is null
    213         * @return the char value of the first letter of the String or the default if null
    214         */
    215        public static char toChar(String str, char defaultValue) {
    216            if (StringUtils.isEmpty(str)) {
    217                return defaultValue;
    218            }
    219            return str.charAt(0);
    220        }
    221
    222        //-----------------------------------------------------------------------
    223        /**
    224         * <p>Converts the character to the Integer it represents, throwing an
    225         * exception if the character is not numeric.</p>
    226         *
    227         * <p>This method coverts the char '1' to the int 1 and so on.</p>
    228         *
    229         * <pre>
    230         *   CharUtils.toIntValue('3')  = 3
    231         *   CharUtils.toIntValue('A')  = IllegalArgumentException
    232         * </pre>
    233         *
    234         * @param ch  the character to convert
    235         * @return the int value of the character
    236         * @throws IllegalArgumentException if the character is not ASCII numeric
    237         */
    238        public static int toIntValue(char ch) {
    239            if (isAsciiNumeric(ch) == false) {
    240                throw new IllegalArgumentException("The character " + ch + " is not in the range '0' - '9'");
    241            }
    242            return ch - 48;
    243        }
    244
    245        /**
    246         * <p>Converts the character to the Integer it represents, throwing an
    247         * exception if the character is not numeric.</p>
    248         *
    249         * <p>This method coverts the char '1' to the int 1 and so on.</p>
    250         *
    251         * <pre>
    252         *   CharUtils.toIntValue('3', -1)  = 3
    253         *   CharUtils.toIntValue('A', -1)  = -1
    254         * </pre>
    255         *
    256         * @param ch  the character to convert
    257         * @param defaultValue  the default value to use if the character is not numeric
    258         * @return the int value of the character
    259         */
    260        public static int toIntValue(char ch, int defaultValue) {
    261            if (isAsciiNumeric(ch) == false) {
    262                return defaultValue;
    263            }
    264            return ch - 48;
    265        }
    266
    267        /**
    268         * <p>Converts the character to the Integer it represents, throwing an
    269         * exception if the character is not numeric.</p>
    270         *
    271         * <p>This method coverts the char '1' to the int 1 and so on.</p>
    272         *
    273         * <pre>
    274         *   CharUtils.toIntValue(null) = IllegalArgumentException
    275         *   CharUtils.toIntValue('3')  = 3
    276         *   CharUtils.toIntValue('A')  = IllegalArgumentException
    277         * </pre>
    278         *
    279         * @param ch  the character to convert, not null
    280         * @return the int value of the character
    281         * @throws IllegalArgumentException if the Character is not ASCII numeric or is null
    282         */
    283        public static int toIntValue(Character ch) {
    284            if (ch == null) {
    285                throw new IllegalArgumentException("The character must not be null");
    286            }
    287            return toIntValue(ch.charValue());
    288        }
    289
    290        /**
    291         * <p>Converts the character to the Integer it represents, throwing an
    292         * exception if the character is not numeric.</p>
    293         *
    294         * <p>This method coverts the char '1' to the int 1 and so on.</p>
    295         *
    296         * <pre>
    297         *   CharUtils.toIntValue(null, -1) = -1
    298         *   CharUtils.toIntValue('3', -1)  = 3
    299         *   CharUtils.toIntValue('A', -1)  = -1
    300         * </pre>
    301         *
    302         * @param ch  the character to convert
    303         * @param defaultValue  the default value to use if the character is not numeric
    304         * @return the int value of the character
    305         */
    306        public static int toIntValue(Character ch, int defaultValue) {
    307            if (ch == null) {
    308                return defaultValue;
    309            }
    310            return toIntValue(ch.charValue(), defaultValue);
    311        }
    312
    313        //-----------------------------------------------------------------------
    314        /**
    315         * <p>Converts the character to a String that contains the one character.</p>
    316         *
    317         * <p>For ASCII 7 bit characters, this uses a cache that will return the
    318         * same String object each time.</p>
    319         *
    320         * <pre>
    321         *   CharUtils.toString(' ')  = " "
    322         *   CharUtils.toString('A')  = "A"
    323         * </pre>
    324         *
    325         * @param ch  the character to convert
    326         * @return a String containing the one specified character
    327         */
    328        public static String toString(char ch) {
    329            if (ch < 128) {
    330                return CHAR_STRING_ARRAY[ch];
    331            }
    332            return new String(new char[] {ch});
    333        }
    334
    335        /**
    336         * <p>Converts the character to a String that contains the one character.</p>
    337         *
    338         * <p>For ASCII 7 bit characters, this uses a cache that will return the
    339         * same String object each time.</p>
    340         *
    341         * <p>If <code>null</code> is passed in, <code>null</code> will be returned.</p>
    342         *
    343         * <pre>
    344         *   CharUtils.toString(null) = null
    345         *   CharUtils.toString(' ')  = " "
    346         *   CharUtils.toString('A')  = "A"
    347         * </pre>
    348         *
    349         * @param ch  the character to convert
    350         * @return a String containing the one specified character
    351         */
    352        public static String toString(Character ch) {
    353            if (ch == null) {
    354                return null;
    355            }
    356            return toString(ch.charValue());
    357        }
    358
    359        //--------------------------------------------------------------------------
    360        /**
    361         * <p>Converts the string to the unicode format '\u0020'.</p>
    362         *
    363         * <p>This format is the Java source code format.</p>
    364         *
    365         * <pre>
    366         *   CharUtils.unicodeEscaped(' ') = "\u0020"
    367         *   CharUtils.unicodeEscaped('A') = "\u0041"
    368         * </pre>
    369         *
    370         * @param ch  the character to convert
    371         * @return the escaped unicode string
    372         */
    373        public static String unicodeEscaped(char ch) {
    374            if (ch < 0x10) {
    375                return "\\u000" + Integer.toHexString(ch);
    376            } else if (ch < 0x100) {
    377                return "\\u00" + Integer.toHexString(ch);
    378            } else if (ch < 0x1000) {
    379                return "\\u0" + Integer.toHexString(ch);
    380            }
    381            return "\\u" + Integer.toHexString(ch);
    382        }
    383
    384        /**
    385         * <p>Converts the string to the unicode format '\u0020'.</p>
    386         *
    387         * <p>This format is the Java source code format.</p>
    388         *
    389         * <p>If <code>null</code> is passed in, <code>null</code> will be returned.</p>
    390         *
    391         * <pre>
    392         *   CharUtils.unicodeEscaped(null) = null
    393         *   CharUtils.unicodeEscaped(' ')  = "\u0020"
    394         *   CharUtils.unicodeEscaped('A')  = "\u0041"
    395         * </pre>
    396         *
    397         * @param ch  the character to convert, may be null
    398         * @return the escaped unicode string, null if null input
    399         */
    400        public static String unicodeEscaped(Character ch) {
    401            if (ch == null) {
    402                return null;
    403            }
    404            return unicodeEscaped(ch.charValue());
    405        }
    406
    407        //--------------------------------------------------------------------------
    408        /**
    409         * <p>Checks whether the character is ASCII 7 bit.</p>
    410         *
    411         * <pre>
    412         *   CharUtils.isAscii('a')  = true
    413         *   CharUtils.isAscii('A')  = true
    414         *   CharUtils.isAscii('3')  = true
    415         *   CharUtils.isAscii('-')  = true
    416         *   CharUtils.isAscii('\n') = true
    417         *   CharUtils.isAscii('&copy;') = false
    418         * </pre>
    419         *
    420         * @param ch  the character to check
    421         * @return true if less than 128
    422         */
    423        public static boolean isAscii(char ch) {
    424            return ch < 128;
    425        }
    426
    427        /**
    428         * <p>Checks whether the character is ASCII 7 bit printable.</p>
    429         *
    430         * <pre>
    431         *   CharUtils.isAsciiPrintable('a')  = true
    432         *   CharUtils.isAsciiPrintable('A')  = true
    433         *   CharUtils.isAsciiPrintable('3')  = true
    434         *   CharUtils.isAsciiPrintable('-')  = true
    435         *   CharUtils.isAsciiPrintable('\n') = false
    436         *   CharUtils.isAsciiPrintable('&copy;') = false
    437         * </pre>
    438         *
    439         * @param ch  the character to check
    440         * @return true if between 32 and 126 inclusive
    441         */
    442        public static boolean isAsciiPrintable(char ch) {
    443            return ch >= 32 && ch < 127;
    444        }
    445
    446        /**
    447         * <p>Checks whether the character is ASCII 7 bit control.</p>
    448         *
    449         * <pre>
    450         *   CharUtils.isAsciiControl('a')  = false
    451         *   CharUtils.isAsciiControl('A')  = false
    452         *   CharUtils.isAsciiControl('3')  = false
    453         *   CharUtils.isAsciiControl('-')  = false
    454         *   CharUtils.isAsciiControl('\n') = true
    455         *   CharUtils.isAsciiControl('&copy;') = false
    456         * </pre>
    457         *
    458         * @param ch  the character to check
    459         * @return true if less than 32 or equals 127
    460         */
    461        public static boolean isAsciiControl(char ch) {
    462            return ch < 32 || ch == 127;
    463        }
    464
    465        /**
    466         * <p>Checks whether the character is ASCII 7 bit alphabetic.</p>
    467         *
    468         * <pre>
    469         *   CharUtils.isAsciiAlpha('a')  = true
    470         *   CharUtils.isAsciiAlpha('A')  = true
    471         *   CharUtils.isAsciiAlpha('3')  = false
    472         *   CharUtils.isAsciiAlpha('-')  = false
    473         *   CharUtils.isAsciiAlpha('\n') = false
    474         *   CharUtils.isAsciiAlpha('&copy;') = false
    475         * </pre>
    476         *
    477         * @param ch  the character to check
    478         * @return true if between 65 and 90 or 97 and 122 inclusive
    479         */
    480        public static boolean isAsciiAlpha(char ch) {
    481            return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z');
    482        }
    483
    484        /**
    485         * <p>Checks whether the character is ASCII 7 bit alphabetic upper case.</p>
    486         *
    487         * <pre>
    488         *   CharUtils.isAsciiAlphaUpper('a')  = false
    489         *   CharUtils.isAsciiAlphaUpper('A')  = true
    490         *   CharUtils.isAsciiAlphaUpper('3')  = false
    491         *   CharUtils.isAsciiAlphaUpper('-')  = false
    492         *   CharUtils.isAsciiAlphaUpper('\n') = false
    493         *   CharUtils.isAsciiAlphaUpper('&copy;') = false
    494         * </pre>
    495         *
    496         * @param ch  the character to check
    497         * @return true if between 65 and 90 inclusive
    498         */
    499        public static boolean isAsciiAlphaUpper(char ch) {
    500            return ch >= 'A' && ch <= 'Z';
    501        }
    502
    503        /**
    504         * <p>Checks whether the character is ASCII 7 bit alphabetic lower case.</p>
    505         *
    506         * <pre>
    507         *   CharUtils.isAsciiAlphaLower('a')  = true
    508         *   CharUtils.isAsciiAlphaLower('A')  = false
    509         *   CharUtils.isAsciiAlphaLower('3')  = false
    510         *   CharUtils.isAsciiAlphaLower('-')  = false
    511         *   CharUtils.isAsciiAlphaLower('\n') = false
    512         *   CharUtils.isAsciiAlphaLower('&copy;') = false
    513         * </pre>
    514         *
    515         * @param ch  the character to check
    516         * @return true if between 97 and 122 inclusive
    517         */
    518        public static boolean isAsciiAlphaLower(char ch) {
    519            return ch >= 'a' && ch <= 'z';
    520        }
    521
    522        /**
    523         * <p>Checks whether the character is ASCII 7 bit numeric.</p>
    524         *
    525         * <pre>
    526         *   CharUtils.isAsciiNumeric('a')  = false
    527         *   CharUtils.isAsciiNumeric('A')  = false
    528         *   CharUtils.isAsciiNumeric('3')  = true
    529         *   CharUtils.isAsciiNumeric('-')  = false
    530         *   CharUtils.isAsciiNumeric('\n') = false
    531         *   CharUtils.isAsciiNumeric('&copy;') = false
    532         * </pre>
    533         *
    534         * @param ch  the character to check
    535         * @return true if between 48 and 57 inclusive
    536         */
    537        public static boolean isAsciiNumeric(char ch) {
    538            return ch >= '0' && ch <= '9';
    539        }
    540
    541        /**
    542         * <p>Checks whether the character is ASCII 7 bit numeric.</p>
    543         *
    544         * <pre>
    545         *   CharUtils.isAsciiAlphanumeric('a')  = true
    546         *   CharUtils.isAsciiAlphanumeric('A')  = true
    547         *   CharUtils.isAsciiAlphanumeric('3')  = true
    548         *   CharUtils.isAsciiAlphanumeric('-')  = false
    549         *   CharUtils.isAsciiAlphanumeric('\n') = false
    550         *   CharUtils.isAsciiAlphanumeric('&copy;') = false
    551         * </pre>
    552         *
    553         * @param ch  the character to check
    554         * @return true if between 48 and 57 or 65 and 90 or 97 and 122 inclusive
    555         */
    556        public static boolean isAsciiAlphanumeric(char ch) {
    557            return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9');
    558        }
    559
    560    }