    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 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     * <p>#ThreadSafe#</p>
    027     * @author Apache Software Foundation
    028     * @since 2.1
    029     * @version $Id: CharUtils.java 918868 2010-03-04 06:22:16Z bayard $
    030     */
    031    public class CharUtils {
    032
    033        private static final String CHAR_STRING =
    034            "\u0000\u0001\u0002\u0003\u0004\u0005\u0006\u0007" +
    035            "\b\t\n\u000b\f\r\u000e\u000f" +
    036            "\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017" +
    037            "\u0018\u0019\u001a\u001b\u001c\u001d\u001e\u001f" +
    038            "\u0020\u0021\"\u0023\u0024\u0025\u0026\u0027" +
    039            "\u0028\u0029\u002a\u002b\u002c\u002d\u002e\u002f" +
    040            "\u0030\u0031\u0032\u0033\u0034\u0035\u0036\u0037" +
    041            "\u0038\u0039\u003a\u003b\u003c\u003d\u003e\u003f" +
    042            "\u0040\u0041\u0042\u0043\u0044\u0045\u0046\u0047" +
    043            "\u0048\u0049\u004a\u004b\u004c\u004d\u004e\u004f" +
    044            "\u0050\u0051\u0052\u0053\u0054\u0055\u0056\u0057" +
    045            "\u0058\u0059\u005a\u005b\\\u005d\u005e\u005f" +
    046            "\u0060\u0061\u0062\u0063\u0064\u0065\u0066\u0067" +
    047            "\u0068\u0069\u006a\u006b\u006c\u006d\u006e\u006f" +
    048            "\u0070\u0071\u0072\u0073\u0074\u0075\u0076\u0077" +
    049            "\u0078\u0079\u007a\u007b\u007c\u007d\u007e\u007f";
    050
    051        private static final String[] CHAR_STRING_ARRAY = new String[128];
    052        private static final Character[] CHAR_ARRAY = new Character[128];
    053
    054        /**
    055         * <code>\u000a</code> linefeed LF ('\n').
    056         *
    057         * @see <a href="http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#101089">JLF: Escape Sequences
    058         *      for Character and String Literals</a>
    059         * @since 2.2
    060         */
    061        public static final char LF = '\n';
    062
    063        /**
    064         * <code>\u000d</code> carriage return CR ('\r').
    065         *
    066         * @see <a href="http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#101089">JLF: Escape Sequences
    067         *      for Character and String Literals</a>
    068         * @since 2.2
    069         */
    070        public static final char CR = '\r';
    071
    072
    073        static {
    074            for (int i = 127; i >= 0; i--) {
    075                CHAR_STRING_ARRAY[i] = CHAR_STRING.substring(i, i + 1);
    076                CHAR_ARRAY[i] = new Character((char) i);
    077            }
    078        }
    079
    080        /**
    081         * <p><code>CharUtils</code> instances should NOT be constructed in standard programming.
    082         * Instead, the class should be used as <code>CharUtils.toString('c');</code>.</p>
    083         *
    084         * <p>This constructor is public to permit tools that require a JavaBean instance
    085         * to operate.</p>
    086         */
    087        public CharUtils() {
    088          super();
    089        }
    090
    091        //-----------------------------------------------------------------------
    092        /**
    093         * <p>Converts the character to a Character.</p>
    094         *
    095         * <p>For ASCII 7 bit characters, this uses a cache that will return the
    096         * same Character object each time.</p>
    097         *
    098         * <pre>
    099         *   CharUtils.toCharacterObject(' ')  = ' '
    100         *   CharUtils.toCharacterObject('A')  = 'A'
    101         * </pre>
    102         *
    103         * @param ch  the character to convert
    104         * @return a Character of the specified character
    105         */
    106        public static Character toCharacterObject(char ch) {
    107            if (ch < CHAR_ARRAY.length) {
    108                return CHAR_ARRAY[ch];
    109            }
    110            return new Character(ch);
    111        }
    112
    113        /**
    114         * <p>Converts the String to a Character using the first character, returning
    115         * null for empty Strings.</p>
    116         *
    117         * <p>For ASCII 7 bit characters, this uses a cache that will return the
    118         * same Character object each time.</p>
    119         *
    120         * <pre>
    121         *   CharUtils.toCharacterObject(null) = null
    122         *   CharUtils.toCharacterObject("")   = null
    123         *   CharUtils.toCharacterObject("A")  = 'A'
    124         *   CharUtils.toCharacterObject("BA") = 'B'
    125         * </pre>
    126         *
    127         * @param str  the character to convert
    128         * @return the Character value of the first letter of the String
    129         */
    130        public static Character toCharacterObject(String str) {
    131            if (StringUtils.isEmpty(str)) {
    132                return null;
    133            }
    134            return toCharacterObject(str.charAt(0));
    135        }
    136
    137        //-----------------------------------------------------------------------
    138        /**
    139         * <p>Converts the Character to a char throwing an exception for <code>null</code>.</p>
    140         *
    141         * <pre>
    142         *   CharUtils.toChar(null) = IllegalArgumentException
    143         *   CharUtils.toChar(' ')  = ' '
    144         *   CharUtils.toChar('A')  = 'A'
    145         * </pre>
    146         *
    147         * @param ch  the character to convert
    148         * @return the char value of the Character
    149         * @throws IllegalArgumentException if the Character is null
    150         */
    151        public static char toChar(Character ch) {
    152            if (ch == null) {
    153                throw new IllegalArgumentException("The Character must not be null");
    154            }
    155            return ch.charValue();
    156        }
    157
    158        /**
    159         * <p>Converts the Character to a char handling <code>null</code>.</p>
    160         *
    161         * <pre>
    162         *   CharUtils.toChar(null, 'X') = 'X'
    163         *   CharUtils.toChar(' ', 'X')  = ' '
    164         *   CharUtils.toChar('A', 'X')  = 'A'
    165         * </pre>
    166         *
    167         * @param ch  the character to convert
    168         * @param defaultValue  the value to use if the  Character is null
    169         * @return the char value of the Character or the default if null
    170         */
    171        public static char toChar(Character ch, char defaultValue) {
    172            if (ch == null) {
    173                return defaultValue;
    174            }
    175            return ch.charValue();
    176        }
    177
    178        //-----------------------------------------------------------------------
    179        /**
    180         * <p>Converts the String to a char using the first character, throwing
    181         * an exception on empty Strings.</p>
    182         *
    183         * <pre>
    184         *   CharUtils.toChar(null) = IllegalArgumentException
    185         *   CharUtils.toChar("")   = IllegalArgumentException
    186         *   CharUtils.toChar("A")  = 'A'
    187         *   CharUtils.toChar("BA") = 'B'
    188         * </pre>
    189         *
    190         * @param str  the character to convert
    191         * @return the char value of the first letter of the String
    192         * @throws IllegalArgumentException if the String is empty
    193         */
    194        public static char toChar(String str) {
    195            if (StringUtils.isEmpty(str)) {
    196                throw new IllegalArgumentException("The String must not be empty");
    197            }
    198            return str.charAt(0);
    199        }
    200
    201        /**
    202         * <p>Converts the String to a char using the first character, defaulting
    203         * the value on empty Strings.</p>
    204         *
    205         * <pre>
    206         *   CharUtils.toChar(null, 'X') = 'X'
    207         *   CharUtils.toChar("", 'X')   = 'X'
    208         *   CharUtils.toChar("A", 'X')  = 'A'
    209         *   CharUtils.toChar("BA", 'X') = 'B'
    210         * </pre>
    211         *
    212         * @param str  the character to convert
    213         * @param defaultValue  the value to use if the  Character is null
    214         * @return the char value of the first letter of the String or the default if null
    215         */
    216        public static char toChar(String str, char defaultValue) {
    217            if (StringUtils.isEmpty(str)) {
    218                return defaultValue;
    219            }
    220            return str.charAt(0);
    221        }
    222
    223        //-----------------------------------------------------------------------
    224        /**
    225         * <p>Converts the character to the Integer it represents, throwing an
    226         * exception if the character is not numeric.</p>
    227         *
    228         * <p>This method coverts the char '1' to the int 1 and so on.</p>
    229         *
    230         * <pre>
    231         *   CharUtils.toIntValue('3')  = 3
    232         *   CharUtils.toIntValue('A')  = IllegalArgumentException
    233         * </pre>
    234         *
    235         * @param ch  the character to convert
    236         * @return the int value of the character
    237         * @throws IllegalArgumentException if the character is not ASCII numeric
    238         */
    239        public static int toIntValue(char ch) {
    240            if (isAsciiNumeric(ch) == false) {
    241                throw new IllegalArgumentException("The character " + ch + " is not in the range '0' - '9'");
    242            }
    243            return ch - 48;
    244        }
    245
    246        /**
    247         * <p>Converts the character to the Integer it represents, throwing an
    248         * exception if the character is not numeric.</p>
    249         *
    250         * <p>This method coverts the char '1' to the int 1 and so on.</p>
    251         *
    252         * <pre>
    253         *   CharUtils.toIntValue('3', -1)  = 3
    254         *   CharUtils.toIntValue('A', -1)  = -1
    255         * </pre>
    256         *
    257         * @param ch  the character to convert
    258         * @param defaultValue  the default value to use if the character is not numeric
    259         * @return the int value of the character
    260         */
    261        public static int toIntValue(char ch, int defaultValue) {
    262            if (isAsciiNumeric(ch) == false) {
    263                return defaultValue;
    264            }
    265            return ch - 48;
    266        }
    267
    268        /**
    269         * <p>Converts the character to the Integer it represents, throwing an
    270         * exception if the character is not numeric.</p>
    271         *
    272         * <p>This method coverts the char '1' to the int 1 and so on.</p>
    273         *
    274         * <pre>
    275         *   CharUtils.toIntValue(null) = IllegalArgumentException
    276         *   CharUtils.toIntValue('3')  = 3
    277         *   CharUtils.toIntValue('A')  = IllegalArgumentException
    278         * </pre>
    279         *
    280         * @param ch  the character to convert, not null
    281         * @return the int value of the character
    282         * @throws IllegalArgumentException if the Character is not ASCII numeric or is null
    283         */
    284        public static int toIntValue(Character ch) {
    285            if (ch == null) {
    286                throw new IllegalArgumentException("The character must not be null");
    287            }
    288            return toIntValue(ch.charValue());
    289        }
    290
    291        /**
    292         * <p>Converts the character to the Integer it represents, throwing an
    293         * exception if the character is not numeric.</p>
    294         *
    295         * <p>This method coverts the char '1' to the int 1 and so on.</p>
    296         *
    297         * <pre>
    298         *   CharUtils.toIntValue(null, -1) = -1
    299         *   CharUtils.toIntValue('3', -1)  = 3
    300         *   CharUtils.toIntValue('A', -1)  = -1
    301         * </pre>
    302         *
    303         * @param ch  the character to convert
    304         * @param defaultValue  the default value to use if the character is not numeric
    305         * @return the int value of the character
    306         */
    307        public static int toIntValue(Character ch, int defaultValue) {
    308            if (ch == null) {
    309                return defaultValue;
    310            }
    311            return toIntValue(ch.charValue(), defaultValue);
    312        }
    313
    314        //-----------------------------------------------------------------------
    315        /**
    316         * <p>Converts the character to a String that contains the one character.</p>
    317         *
    318         * <p>For ASCII 7 bit characters, this uses a cache that will return the
    319         * same String object each time.</p>
    320         *
    321         * <pre>
    322         *   CharUtils.toString(' ')  = " "
    323         *   CharUtils.toString('A')  = "A"
    324         * </pre>
    325         *
    326         * @param ch  the character to convert
    327         * @return a String containing the one specified character
    328         */
    329        public static String toString(char ch) {
    330            if (ch < 128) {
    331                return CHAR_STRING_ARRAY[ch];
    332            }
    333            return new String(new char[] {ch});
    334        }
    335
    336        /**
    337         * <p>Converts the character to a String that contains the one character.</p>
    338         *
    339         * <p>For ASCII 7 bit characters, this uses a cache that will return the
    340         * same String object each time.</p>
    341         *
    342         * <p>If <code>null</code> is passed in, <code>null</code> will be returned.</p>
    343         *
    344         * <pre>
    345         *   CharUtils.toString(null) = null
    346         *   CharUtils.toString(' ')  = " "
    347         *   CharUtils.toString('A')  = "A"
    348         * </pre>
    349         *
    350         * @param ch  the character to convert
    351         * @return a String containing the one specified character
    352         */
    353        public static String toString(Character ch) {
    354            if (ch == null) {
    355                return null;
    356            }
    357            return toString(ch.charValue());
    358        }
    359
    360        //--------------------------------------------------------------------------
    361        /**
    362         * <p>Converts the string to the unicode format '\u0020'.</p>
    363         *
    364         * <p>This format is the Java source code format.</p>
    365         *
    366         * <pre>
    367         *   CharUtils.unicodeEscaped(' ') = "\u0020"
    368         *   CharUtils.unicodeEscaped('A') = "\u0041"
    369         * </pre>
    370         *
    371         * @param ch  the character to convert
    372         * @return the escaped unicode string
    373         */
    374        public static String unicodeEscaped(char ch) {
    375            if (ch < 0x10) {
    376                return "\\u000" + Integer.toHexString(ch);
    377            } else if (ch < 0x100) {
    378                return "\\u00" + Integer.toHexString(ch);
    379            } else if (ch < 0x1000) {
    380                return "\\u0" + Integer.toHexString(ch);
    381            }
    382            return "\\u" + Integer.toHexString(ch);
    383        }
    384
    385        /**
    386         * <p>Converts the string to the unicode format '\u0020'.</p>
    387         *
    388         * <p>This format is the Java source code format.</p>
    389         *
    390         * <p>If <code>null</code> is passed in, <code>null</code> will be returned.</p>
    391         *
    392         * <pre>
    393         *   CharUtils.unicodeEscaped(null) = null
    394         *   CharUtils.unicodeEscaped(' ')  = "\u0020"
    395         *   CharUtils.unicodeEscaped('A')  = "\u0041"
    396         * </pre>
    397         *
    398         * @param ch  the character to convert, may be null
    399         * @return the escaped unicode string, null if null input
    400         */
    401        public static String unicodeEscaped(Character ch) {
    402            if (ch == null) {
    403                return null;
    404            }
    405            return unicodeEscaped(ch.charValue());
    406        }
    407
    408        //--------------------------------------------------------------------------
    409        /**
    410         * <p>Checks whether the character is ASCII 7 bit.</p>
    411         *
    412         * <pre>
    413         *   CharUtils.isAscii('a')  = true
    414         *   CharUtils.isAscii('A')  = true
    415         *   CharUtils.isAscii('3')  = true
    416         *   CharUtils.isAscii('-')  = true
    417         *   CharUtils.isAscii('\n') = true
    418         *   CharUtils.isAscii('&copy;') = false
    419         * </pre>
    420         *
    421         * @param ch  the character to check
    422         * @return true if less than 128
    423         */
    424        public static boolean isAscii(char ch) {
    425            return ch < 128;
    426        }
    427
    428        /**
    429         * <p>Checks whether the character is ASCII 7 bit printable.</p>
    430         *
    431         * <pre>
    432         *   CharUtils.isAsciiPrintable('a')  = true
    433         *   CharUtils.isAsciiPrintable('A')  = true
    434         *   CharUtils.isAsciiPrintable('3')  = true
    435         *   CharUtils.isAsciiPrintable('-')  = true
    436         *   CharUtils.isAsciiPrintable('\n') = false
    437         *   CharUtils.isAsciiPrintable('&copy;') = false
    438         * </pre>
    439         *
    440         * @param ch  the character to check
    441         * @return true if between 32 and 126 inclusive
    442         */
    443        public static boolean isAsciiPrintable(char ch) {
    444            return ch >= 32 && ch < 127;
    445        }
    446
    447        /**
    448         * <p>Checks whether the character is ASCII 7 bit control.</p>
    449         *
    450         * <pre>
    451         *   CharUtils.isAsciiControl('a')  = false
    452         *   CharUtils.isAsciiControl('A')  = false
    453         *   CharUtils.isAsciiControl('3')  = false
    454         *   CharUtils.isAsciiControl('-')  = false
    455         *   CharUtils.isAsciiControl('\n') = true
    456         *   CharUtils.isAsciiControl('&copy;') = false
    457         * </pre>
    458         *
    459         * @param ch  the character to check
    460         * @return true if less than 32 or equals 127
    461         */
    462        public static boolean isAsciiControl(char ch) {
    463            return ch < 32 || ch == 127;
    464        }
    465
    466        /**
    467         * <p>Checks whether the character is ASCII 7 bit alphabetic.</p>
    468         *
    469         * <pre>
    470         *   CharUtils.isAsciiAlpha('a')  = true
    471         *   CharUtils.isAsciiAlpha('A')  = true
    472         *   CharUtils.isAsciiAlpha('3')  = false
    473         *   CharUtils.isAsciiAlpha('-')  = false
    474         *   CharUtils.isAsciiAlpha('\n') = false
    475         *   CharUtils.isAsciiAlpha('&copy;') = false
    476         * </pre>
    477         *
    478         * @param ch  the character to check
    479         * @return true if between 65 and 90 or 97 and 122 inclusive
    480         */
    481        public static boolean isAsciiAlpha(char ch) {
    482            return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z');
    483        }
    484
    485        /**
    486         * <p>Checks whether the character is ASCII 7 bit alphabetic upper case.</p>
    487         *
    488         * <pre>
    489         *   CharUtils.isAsciiAlphaUpper('a')  = false
    490         *   CharUtils.isAsciiAlphaUpper('A')  = true
    491         *   CharUtils.isAsciiAlphaUpper('3')  = false
    492         *   CharUtils.isAsciiAlphaUpper('-')  = false
    493         *   CharUtils.isAsciiAlphaUpper('\n') = false
    494         *   CharUtils.isAsciiAlphaUpper('&copy;') = false
    495         * </pre>
    496         *
    497         * @param ch  the character to check
    498         * @return true if between 65 and 90 inclusive
    499         */
    500        public static boolean isAsciiAlphaUpper(char ch) {
    501            return ch >= 'A' && ch <= 'Z';
    502        }
    503
    504        /**
    505         * <p>Checks whether the character is ASCII 7 bit alphabetic lower case.</p>
    506         *
    507         * <pre>
    508         *   CharUtils.isAsciiAlphaLower('a')  = true
    509         *   CharUtils.isAsciiAlphaLower('A')  = false
    510         *   CharUtils.isAsciiAlphaLower('3')  = false
    511         *   CharUtils.isAsciiAlphaLower('-')  = false
    512         *   CharUtils.isAsciiAlphaLower('\n') = false
    513         *   CharUtils.isAsciiAlphaLower('&copy;') = false
    514         * </pre>
    515         *
    516         * @param ch  the character to check
    517         * @return true if between 97 and 122 inclusive
    518         */
    519        public static boolean isAsciiAlphaLower(char ch) {
    520            return ch >= 'a' && ch <= 'z';
    521        }
    522
    523        /**
    524         * <p>Checks whether the character is ASCII 7 bit numeric.</p>
    525         *
    526         * <pre>
    527         *   CharUtils.isAsciiNumeric('a')  = false
    528         *   CharUtils.isAsciiNumeric('A')  = false
    529         *   CharUtils.isAsciiNumeric('3')  = true
    530         *   CharUtils.isAsciiNumeric('-')  = false
    531         *   CharUtils.isAsciiNumeric('\n') = false
    532         *   CharUtils.isAsciiNumeric('&copy;') = false
    533         * </pre>
    534         *
    535         * @param ch  the character to check
    536         * @return true if between 48 and 57 inclusive
    537         */
    538        public static boolean isAsciiNumeric(char ch) {
    539            return ch >= '0' && ch <= '9';
    540        }
    541
    542        /**
    543         * <p>Checks whether the character is ASCII 7 bit numeric.</p>
    544         *
    545         * <pre>
    546         *   CharUtils.isAsciiAlphanumeric('a')  = true
    547         *   CharUtils.isAsciiAlphanumeric('A')  = true
    548         *   CharUtils.isAsciiAlphanumeric('3')  = true
    549         *   CharUtils.isAsciiAlphanumeric('-')  = false
    550         *   CharUtils.isAsciiAlphanumeric('\n') = false
    551         *   CharUtils.isAsciiAlphanumeric('&copy;') = false
    552         * </pre>
    553         *
    554         * @param ch  the character to check
    555         * @return true if between 48 and 57 or 65 and 90 or 97 and 122 inclusive
    556         */
    557        public static boolean isAsciiAlphanumeric(char ch) {
    558            return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9');
    559        }
    560
    561    }