Operations on char primitives and Character objects.
* *This class tries to handle null input gracefully.
* An exception will not be thrown for a null input.
* Each method documents its behaviour in more detail.
#ThreadSafe#
* @author Apache Software Foundation * @since 2.1 * */ public class CharUtils { private static final String CHAR_STRING = "\u0000\u0001\u0002\u0003\u0004\u0005\u0006\u0007" + "\b\t\n\u000b\f\r\u000e\u000f" + "\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017" + "\u0018\u0019\u001a\u001b\u001c\u001d\u001e\u001f" + "\u0020\u0021\"\u0023\u0024\u0025\u0026\u0027" + "\u0028\u0029\u002a\u002b\u002c\u002d\u002e\u002f" + "\u0030\u0031\u0032\u0033\u0034\u0035\u0036\u0037" + "\u0038\u0039\u003a\u003b\u003c\u003d\u003e\u003f" + "\u0040\u0041\u0042\u0043\u0044\u0045\u0046\u0047" + "\u0048\u0049\u004a\u004b\u004c\u004d\u004e\u004f" + "\u0050\u0051\u0052\u0053\u0054\u0055\u0056\u0057" + "\u0058\u0059\u005a\u005b\\\u005d\u005e\u005f" + "\u0060\u0061\u0062\u0063\u0064\u0065\u0066\u0067" + "\u0068\u0069\u006a\u006b\u006c\u006d\u006e\u006f" + "\u0070\u0071\u0072\u0073\u0074\u0075\u0076\u0077" + "\u0078\u0079\u007a\u007b\u007c\u007d\u007e\u007f"; private static final String[] CHAR_STRING_ARRAY = new String[128]; private static final Character[] CHAR_ARRAY = new Character[128]; /** *\u000a linefeed LF ('\n').
*
* @see JLF: Escape Sequences
* for Character and String Literals
* @since 2.2
*/
public static final char LF = '\n';
/**
* \u000d carriage return CR ('\r').
*
* @see JLF: Escape Sequences
* for Character and String Literals
* @since 2.2
*/
public static final char CR = '\r';
static {
for (int i = 127; i >= 0; i--) {
CHAR_STRING_ARRAY[i] = CHAR_STRING.substring(i, i + 1);
CHAR_ARRAY[i] = new Character((char) i);
}
}
/**
* CharUtils instances should NOT be constructed in standard programming.
* Instead, the class should be used as CharUtils.toString('c');.
This constructor is public to permit tools that require a JavaBean instance * to operate.
*/ public CharUtils() { super(); } //----------------------------------------------------------------------- /** *Converts the character to a Character.
* *For ASCII 7 bit characters, this uses a cache that will return the * same Character object each time.
* *
* CharUtils.toCharacterObject(' ') = ' '
* CharUtils.toCharacterObject('A') = 'A'
*
*
* @param ch the character to convert
* @return a Character of the specified character
*/
public static Character toCharacterObject(char ch) {
if (ch < CHAR_ARRAY.length) {
return CHAR_ARRAY[ch];
}
return new Character(ch);
}
/**
* Converts the String to a Character using the first character, returning * null for empty Strings.
* *For ASCII 7 bit characters, this uses a cache that will return the * same Character object each time.
* *
* CharUtils.toCharacterObject(null) = null
* CharUtils.toCharacterObject("") = null
* CharUtils.toCharacterObject("A") = 'A'
* CharUtils.toCharacterObject("BA") = 'B'
*
*
* @param str the character to convert
* @return the Character value of the first letter of the String
*/
public static Character toCharacterObject(String str) {
if (StringUtils.isEmpty(str)) {
return null;
}
return toCharacterObject(str.charAt(0));
}
//-----------------------------------------------------------------------
/**
* Converts the Character to a char throwing an exception for null.
* CharUtils.toChar(null) = IllegalArgumentException
* CharUtils.toChar(' ') = ' '
* CharUtils.toChar('A') = 'A'
*
*
* @param ch the character to convert
* @return the char value of the Character
* @throws IllegalArgumentException if the Character is null
*/
public static char toChar(Character ch) {
if (ch == null) {
throw new IllegalArgumentException("The Character must not be null");
}
return ch.charValue();
}
/**
* Converts the Character to a char handling null.
* CharUtils.toChar(null, 'X') = 'X'
* CharUtils.toChar(' ', 'X') = ' '
* CharUtils.toChar('A', 'X') = 'A'
*
*
* @param ch the character to convert
* @param defaultValue the value to use if the Character is null
* @return the char value of the Character or the default if null
*/
public static char toChar(Character ch, char defaultValue) {
if (ch == null) {
return defaultValue;
}
return ch.charValue();
}
//-----------------------------------------------------------------------
/**
* Converts the String to a char using the first character, throwing * an exception on empty Strings.
* *
* CharUtils.toChar(null) = IllegalArgumentException
* CharUtils.toChar("") = IllegalArgumentException
* CharUtils.toChar("A") = 'A'
* CharUtils.toChar("BA") = 'B'
*
*
* @param str the character to convert
* @return the char value of the first letter of the String
* @throws IllegalArgumentException if the String is empty
*/
public static char toChar(String str) {
if (StringUtils.isEmpty(str)) {
throw new IllegalArgumentException("The String must not be empty");
}
return str.charAt(0);
}
/**
* Converts the String to a char using the first character, defaulting * the value on empty Strings.
* *
* CharUtils.toChar(null, 'X') = 'X'
* CharUtils.toChar("", 'X') = 'X'
* CharUtils.toChar("A", 'X') = 'A'
* CharUtils.toChar("BA", 'X') = 'B'
*
*
* @param str the character to convert
* @param defaultValue the value to use if the Character is null
* @return the char value of the first letter of the String or the default if null
*/
public static char toChar(String str, char defaultValue) {
if (StringUtils.isEmpty(str)) {
return defaultValue;
}
return str.charAt(0);
}
//-----------------------------------------------------------------------
/**
* Converts the character to the Integer it represents, throwing an * exception if the character is not numeric.
* *This method coverts the char '1' to the int 1 and so on.
* *
* CharUtils.toIntValue('3') = 3
* CharUtils.toIntValue('A') = IllegalArgumentException
*
*
* @param ch the character to convert
* @return the int value of the character
* @throws IllegalArgumentException if the character is not ASCII numeric
*/
public static int toIntValue(char ch) {
if (isAsciiNumeric(ch) == false) {
throw new IllegalArgumentException("The character " + ch + " is not in the range '0' - '9'");
}
return ch - 48;
}
/**
* Converts the character to the Integer it represents, throwing an * exception if the character is not numeric.
* *This method coverts the char '1' to the int 1 and so on.
* *
* CharUtils.toIntValue('3', -1) = 3
* CharUtils.toIntValue('A', -1) = -1
*
*
* @param ch the character to convert
* @param defaultValue the default value to use if the character is not numeric
* @return the int value of the character
*/
public static int toIntValue(char ch, int defaultValue) {
if (isAsciiNumeric(ch) == false) {
return defaultValue;
}
return ch - 48;
}
/**
* Converts the character to the Integer it represents, throwing an * exception if the character is not numeric.
* *This method coverts the char '1' to the int 1 and so on.
* *
* CharUtils.toIntValue(null) = IllegalArgumentException
* CharUtils.toIntValue('3') = 3
* CharUtils.toIntValue('A') = IllegalArgumentException
*
*
* @param ch the character to convert, not null
* @return the int value of the character
* @throws IllegalArgumentException if the Character is not ASCII numeric or is null
*/
public static int toIntValue(Character ch) {
if (ch == null) {
throw new IllegalArgumentException("The character must not be null");
}
return toIntValue(ch.charValue());
}
/**
* Converts the character to the Integer it represents, throwing an * exception if the character is not numeric.
* *This method coverts the char '1' to the int 1 and so on.
* *
* CharUtils.toIntValue(null, -1) = -1
* CharUtils.toIntValue('3', -1) = 3
* CharUtils.toIntValue('A', -1) = -1
*
*
* @param ch the character to convert
* @param defaultValue the default value to use if the character is not numeric
* @return the int value of the character
*/
public static int toIntValue(Character ch, int defaultValue) {
if (ch == null) {
return defaultValue;
}
return toIntValue(ch.charValue(), defaultValue);
}
//-----------------------------------------------------------------------
/**
* Converts the character to a String that contains the one character.
* *For ASCII 7 bit characters, this uses a cache that will return the * same String object each time.
* *
* CharUtils.toString(' ') = " "
* CharUtils.toString('A') = "A"
*
*
* @param ch the character to convert
* @return a String containing the one specified character
*/
public static String toString(char ch) {
if (ch < 128) {
return CHAR_STRING_ARRAY[ch];
}
return new String(new char[] {ch});
}
/**
* Converts the character to a String that contains the one character.
* *For ASCII 7 bit characters, this uses a cache that will return the * same String object each time.
* *If null is passed in, null will be returned.
* CharUtils.toString(null) = null
* CharUtils.toString(' ') = " "
* CharUtils.toString('A') = "A"
*
*
* @param ch the character to convert
* @return a String containing the one specified character
*/
public static String toString(Character ch) {
if (ch == null) {
return null;
}
return toString(ch.charValue());
}
//--------------------------------------------------------------------------
/**
* Converts the string to the unicode format '\u0020'.
* *This format is the Java source code format.
* *
* CharUtils.unicodeEscaped(' ') = "\u0020"
* CharUtils.unicodeEscaped('A') = "\u0041"
*
*
* @param ch the character to convert
* @return the escaped unicode string
*/
public static String unicodeEscaped(char ch) {
if (ch < 0x10) {
return "\\u000" + Integer.toHexString(ch);
} else if (ch < 0x100) {
return "\\u00" + Integer.toHexString(ch);
} else if (ch < 0x1000) {
return "\\u0" + Integer.toHexString(ch);
}
return "\\u" + Integer.toHexString(ch);
}
/**
* Converts the string to the unicode format '\u0020'.
* *This format is the Java source code format.
* *If null is passed in, null will be returned.
* CharUtils.unicodeEscaped(null) = null
* CharUtils.unicodeEscaped(' ') = "\u0020"
* CharUtils.unicodeEscaped('A') = "\u0041"
*
*
* @param ch the character to convert, may be null
* @return the escaped unicode string, null if null input
*/
public static String unicodeEscaped(Character ch) {
if (ch == null) {
return null;
}
return unicodeEscaped(ch.charValue());
}
//--------------------------------------------------------------------------
/**
* Checks whether the character is ASCII 7 bit.
* *
* CharUtils.isAscii('a') = true
* CharUtils.isAscii('A') = true
* CharUtils.isAscii('3') = true
* CharUtils.isAscii('-') = true
* CharUtils.isAscii('\n') = true
* CharUtils.isAscii('©') = false
*
*
* @param ch the character to check
* @return true if less than 128
*/
public static boolean isAscii(char ch) {
return ch < 128;
}
/**
* Checks whether the character is ASCII 7 bit printable.
* *
* CharUtils.isAsciiPrintable('a') = true
* CharUtils.isAsciiPrintable('A') = true
* CharUtils.isAsciiPrintable('3') = true
* CharUtils.isAsciiPrintable('-') = true
* CharUtils.isAsciiPrintable('\n') = false
* CharUtils.isAsciiPrintable('©') = false
*
*
* @param ch the character to check
* @return true if between 32 and 126 inclusive
*/
public static boolean isAsciiPrintable(char ch) {
return ch >= 32 && ch < 127;
}
/**
* Checks whether the character is ASCII 7 bit control.
* *
* CharUtils.isAsciiControl('a') = false
* CharUtils.isAsciiControl('A') = false
* CharUtils.isAsciiControl('3') = false
* CharUtils.isAsciiControl('-') = false
* CharUtils.isAsciiControl('\n') = true
* CharUtils.isAsciiControl('©') = false
*
*
* @param ch the character to check
* @return true if less than 32 or equals 127
*/
public static boolean isAsciiControl(char ch) {
return ch < 32 || ch == 127;
}
/**
* Checks whether the character is ASCII 7 bit alphabetic.
* *
* CharUtils.isAsciiAlpha('a') = true
* CharUtils.isAsciiAlpha('A') = true
* CharUtils.isAsciiAlpha('3') = false
* CharUtils.isAsciiAlpha('-') = false
* CharUtils.isAsciiAlpha('\n') = false
* CharUtils.isAsciiAlpha('©') = false
*
*
* @param ch the character to check
* @return true if between 65 and 90 or 97 and 122 inclusive
*/
public static boolean isAsciiAlpha(char ch) {
return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z');
}
/**
* Checks whether the character is ASCII 7 bit alphabetic upper case.
* *
* CharUtils.isAsciiAlphaUpper('a') = false
* CharUtils.isAsciiAlphaUpper('A') = true
* CharUtils.isAsciiAlphaUpper('3') = false
* CharUtils.isAsciiAlphaUpper('-') = false
* CharUtils.isAsciiAlphaUpper('\n') = false
* CharUtils.isAsciiAlphaUpper('©') = false
*
*
* @param ch the character to check
* @return true if between 65 and 90 inclusive
*/
public static boolean isAsciiAlphaUpper(char ch) {
return ch >= 'A' && ch <= 'Z';
}
/**
* Checks whether the character is ASCII 7 bit alphabetic lower case.
* *
* CharUtils.isAsciiAlphaLower('a') = true
* CharUtils.isAsciiAlphaLower('A') = false
* CharUtils.isAsciiAlphaLower('3') = false
* CharUtils.isAsciiAlphaLower('-') = false
* CharUtils.isAsciiAlphaLower('\n') = false
* CharUtils.isAsciiAlphaLower('©') = false
*
*
* @param ch the character to check
* @return true if between 97 and 122 inclusive
*/
public static boolean isAsciiAlphaLower(char ch) {
return ch >= 'a' && ch <= 'z';
}
/**
* Checks whether the character is ASCII 7 bit numeric.
* *
* CharUtils.isAsciiNumeric('a') = false
* CharUtils.isAsciiNumeric('A') = false
* CharUtils.isAsciiNumeric('3') = true
* CharUtils.isAsciiNumeric('-') = false
* CharUtils.isAsciiNumeric('\n') = false
* CharUtils.isAsciiNumeric('©') = false
*
*
* @param ch the character to check
* @return true if between 48 and 57 inclusive
*/
public static boolean isAsciiNumeric(char ch) {
return ch >= '0' && ch <= '9';
}
/**
* Checks whether the character is ASCII 7 bit numeric.
* *
* CharUtils.isAsciiAlphanumeric('a') = true
* CharUtils.isAsciiAlphanumeric('A') = true
* CharUtils.isAsciiAlphanumeric('3') = true
* CharUtils.isAsciiAlphanumeric('-') = false
* CharUtils.isAsciiAlphanumeric('\n') = false
* CharUtils.isAsciiAlphanumeric('©') = false
*
*
* @param ch the character to check
* @return true if between 48 and 57 or 65 and 90 or 97 and 122 inclusive
*/
public static boolean isAsciiAlphanumeric(char ch) {
return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9');
}
// ----------------- Following code copied from Apache Harmony (Character class)
/**
* Indicates whether {@code ch} is a high- (or leading-) surrogate code unit
* that is used for representing supplementary characters in UTF-16
* encoding.
*
* @param ch
* the character to test.
* @return {@code true} if {@code ch} is a high-surrogate code unit;
* {@code false} otherwise.
*/
static boolean isHighSurrogate(char ch) {
return ('\uD800' <= ch && '\uDBFF' >= ch);
}
}