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Apache Commons Lang, a package of Java utility classes for the
classes that are in java.lang's hierarchy, or are considered to be so
standard as to justify existence in java.lang.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.lang3;
/**
* Operations on char primitives and Character objects.
*
* This class tries to handle {@code null} input gracefully.
* An exception will not be thrown for a {@code null} input.
* Each method documents its behavior in more detail.
*
* #ThreadSafe#
* @since 2.1
*/
public class CharUtils {
private static final String[] CHAR_STRING_ARRAY = new String[128];
private static final char[] HEX_DIGITS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
/**
* Linefeed character LF ({@code '\n'}, Unicode 000a).
*
* @see JLF: Escape Sequences
* for Character and String Literals
* @since 2.2
*/
public static final char LF = '\n';
/**
* Carriage return characterf CR ('\r', Unicode 000d).
*
* @see JLF: Escape Sequences
* for Character and String Literals
* @since 2.2
*/
public static final char CR = '\r';
/**
* {@code \u0000} null control character ('\0'), abbreviated NUL.
*
* @since 3.6
*/
public static final char NUL = '\0';
static {
for (char c = 0; c < CHAR_STRING_ARRAY.length; c++) {
CHAR_STRING_ARRAY[c] = String.valueOf(c);
}
}
/**
* {@code CharUtils} instances should NOT be constructed in standard programming.
* Instead, the class should be used as {@code CharUtils.toString('c');}.
*
* This constructor is public to permit tools that require a JavaBean instance
* to operate.
*/
public CharUtils() {
}
//-----------------------------------------------------------------------
/**
* 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'
*
*
* @deprecated Java 5 introduced {@link Character#valueOf(char)} which caches chars 0 through 127.
* @param ch the character to convert
* @return a Character of the specified character
*/
@Deprecated
public static Character toCharacterObject(final char ch) {
return Character.valueOf(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(final String str) {
if (StringUtils.isEmpty(str)) {
return null;
}
return Character.valueOf(str.charAt(0));
}
//-----------------------------------------------------------------------
/**
* Converts the Character to a char throwing an exception for {@code null}.
*
*
* CharUtils.toChar(' ') = ' '
* CharUtils.toChar('A') = 'A'
* CharUtils.toChar(null) throws IllegalArgumentException
*
*
* @param ch the character to convert
* @return the char value of the Character
* @throws NullPointerException if the Character is null
*/
public static char toChar(final Character ch) {
Validate.notNull(ch, "ch");
return ch.charValue();
}
/**
* Converts the Character to a char handling {@code 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(final Character ch, final 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("A") = 'A'
* CharUtils.toChar("BA") = 'B'
* CharUtils.toChar(null) throws IllegalArgumentException
* CharUtils.toChar("") throws IllegalArgumentException
*
*
* @param str the character to convert
* @return the char value of the first letter of the String
* @throws NullPointerException if the string is null
* @throws IllegalArgumentException if the String is empty
*/
public static char toChar(final String str) {
Validate.notEmpty(str, "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(final String str, final 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 converts the char '1' to the int 1 and so on.
*
*
* CharUtils.toIntValue('3') = 3
* CharUtils.toIntValue('A') throws 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(final char ch) {
if (!isAsciiNumeric(ch)) {
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 converts 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(final char ch, final int defaultValue) {
if (!isAsciiNumeric(ch)) {
return defaultValue;
}
return ch - 48;
}
/**
* Converts the character to the Integer it represents, throwing an
* exception if the character is not numeric.
*
* This method converts the char '1' to the int 1 and so on.
*
*
* CharUtils.toIntValue('3') = 3
* CharUtils.toIntValue(null) throws IllegalArgumentException
* CharUtils.toIntValue('A') throws IllegalArgumentException
*
*
* @param ch the character to convert, not null
* @return the int value of the character
* @throws NullPointerException if the Character is null
* @throws IllegalArgumentException if the Character is not ASCII numeric
*/
public static int toIntValue(final Character ch) {
Validate.notNull(ch, "ch");
return toIntValue(ch.charValue());
}
/**
* Converts the character to the Integer it represents, throwing an
* exception if the character is not numeric.
*
* This method converts 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(final Character ch, final 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(final 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 {@code null} is passed in, {@code 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(final 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(final char ch) {
return "\\u" +
HEX_DIGITS[(ch >> 12) & 15] +
HEX_DIGITS[(ch >> 8) & 15] +
HEX_DIGITS[(ch >> 4) & 15] +
HEX_DIGITS[(ch) & 15];
}
/**
* Converts the string to the Unicode format '\u0020'.
*
* This format is the Java source code format.
*
* If {@code null} is passed in, {@code 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(final 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(final 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(final 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(final 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(final char ch) {
return isAsciiAlphaUpper(ch) || isAsciiAlphaLower(ch);
}
/**
* 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(final 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(final 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(final 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(final char ch) {
return isAsciiAlpha(ch) || isAsciiNumeric(ch);
}
/**
* Compares two {@code char} values numerically. This is the same functionality as provided in Java 7.
*
* @param x the first {@code char} to compare
* @param y the second {@code char} to compare
* @return the value {@code 0} if {@code x == y};
* a value less than {@code 0} if {@code x < y}; and
* a value greater than {@code 0} if {@code x > y}
* @since 3.4
*/
public static int compare(final char x, final char y) {
return x-y;
}
}