Class CharMatcher

java.lang.Object
com.google.common.base.CharMatcher
All Implemented Interfaces:
Predicate<Character>, Predicate<Character>
Direct Known Subclasses:
CharMatcher.And, CharMatcher.AnyOf, CharMatcher.BreakingWhitespace, CharMatcher.FastMatcher, CharMatcher.ForPredicate, CharMatcher.JavaDigit, CharMatcher.JavaLetter, CharMatcher.JavaLetterOrDigit, CharMatcher.JavaLowerCase, CharMatcher.JavaUpperCase, CharMatcher.Negated, CharMatcher.Or, CharMatcher.RangesMatcher

public abstract class CharMatcher extends Object implements Predicate<Character>
Determines a true or false value for any Java char value, just as Predicate does for any Object. Also offers basic text processing methods based on this function. Implementations are strongly encouraged to be side-effect-free and immutable.

Throughout the documentation of this class, the phrase "matching character" is used to mean "any char value c for which this.matches(c) returns true".

Warning: This class deals only with char values, that is, BMP characters. It does not understand supplementary Unicode code points in the range 0x10000 to 0x10FFFF which includes the majority of assigned characters, including important CJK characters and emoji.

Supplementary characters are encoded into a String using surrogate pairs, and a CharMatcher treats these just as two separate characters. countIn(java.lang.CharSequence) counts each supplementary character as 2 chars.

For up-to-date Unicode character properties (digit, letter, etc.) and support for supplementary code points, use ICU4J UCharacter and UnicodeSet (freeze() after building). For basic text processing based on UnicodeSet use the ICU4J UnicodeSetSpanner.

Example usages:

   String trimmed = whitespace().trimFrom(userInput);
   if (ascii().matchesAllOf(s)) { ... }

See the Guava User Guide article on CharMatcher .

Since:
1.0
  • Field Details

  • Constructor Details

    • CharMatcher

      protected CharMatcher()
      Constructor for use by subclasses. When subclassing, you may want to override toString() to provide a useful description.
  • Method Details

    • any

      public static CharMatcher any()
      Matches any character.
      Since:
      19.0 (since 1.0 as constant ANY)
    • none

      public static CharMatcher none()
      Matches no characters.
      Since:
      19.0 (since 1.0 as constant NONE)
    • whitespace

      public static CharMatcher whitespace()
      Determines whether a character is whitespace according to the latest Unicode standard, as illustrated here. This is not the same definition used by other Java APIs. (See a comparison of several definitions of "whitespace".)

      All Unicode White_Space characters are on the BMP and thus supported by this API.

      Note: as the Unicode definition evolves, we will modify this matcher to keep it up to date.

      Since:
      19.0 (since 1.0 as constant WHITESPACE)
    • breakingWhitespace

      public static CharMatcher breakingWhitespace()
      Determines whether a character is a breaking whitespace (that is, a whitespace which can be interpreted as a break between words for formatting purposes). See whitespace() for a discussion of that term.
      Since:
      19.0 (since 2.0 as constant BREAKING_WHITESPACE)
    • ascii

      public static CharMatcher ascii()
      Determines whether a character is ASCII, meaning that its code point is less than 128.
      Since:
      19.0 (since 1.0 as constant ASCII)
    • digit

      @Deprecated public static CharMatcher digit()
      Deprecated.
      Many digits are supplementary characters; see the class documentation.
      Determines whether a character is a BMP digit according to Unicode. If you only care to match ASCII digits, you can use inRange('0', '9').
      Since:
      19.0 (since 1.0 as constant DIGIT)
    • javaDigit

      @Deprecated public static CharMatcher javaDigit()
      Deprecated.
      Many digits are supplementary characters; see the class documentation.
      Determines whether a character is a BMP digit according to Java's definition. If you only care to match ASCII digits, you can use inRange('0', '9').
      Since:
      19.0 (since 1.0 as constant JAVA_DIGIT)
    • javaLetter

      @Deprecated public static CharMatcher javaLetter()
      Deprecated.
      Most letters are supplementary characters; see the class documentation.
      Determines whether a character is a BMP letter according to Java's definition. If you only care to match letters of the Latin alphabet, you can use inRange('a', 'z').or(inRange('A', 'Z')).
      Since:
      19.0 (since 1.0 as constant JAVA_LETTER)
    • javaLetterOrDigit

      @Deprecated public static CharMatcher javaLetterOrDigit()
      Deprecated.
      Most letters and digits are supplementary characters; see the class documentation.
      Determines whether a character is a BMP letter or digit according to Java's definition.
      Since:
      19.0 (since 1.0 as constant JAVA_LETTER_OR_DIGIT).
    • javaUpperCase

      @Deprecated public static CharMatcher javaUpperCase()
      Deprecated.
      Some uppercase characters are supplementary characters; see the class documentation.
      Determines whether a BMP character is upper case according to Java's definition.
      Since:
      19.0 (since 1.0 as constant JAVA_UPPER_CASE)
    • javaLowerCase

      @Deprecated public static CharMatcher javaLowerCase()
      Deprecated.
      Some lowercase characters are supplementary characters; see the class documentation.
      Determines whether a BMP character is lower case according to Java's definition.
      Since:
      19.0 (since 1.0 as constant JAVA_LOWER_CASE)
    • javaIsoControl

      public static CharMatcher javaIsoControl()
      Determines whether a character is an ISO control character as specified by Character.isISOControl(char).

      All ISO control codes are on the BMP and thus supported by this API.

      Since:
      19.0 (since 1.0 as constant JAVA_ISO_CONTROL)
    • invisible

      @Deprecated public static CharMatcher invisible()
      Deprecated.
      Most invisible characters are supplementary characters; see the class documentation.
      Determines whether a character is invisible; that is, if its Unicode category is any of SPACE_SEPARATOR, LINE_SEPARATOR, PARAGRAPH_SEPARATOR, CONTROL, FORMAT, SURROGATE, and PRIVATE_USE according to ICU4J.

      See also the Unicode Default_Ignorable_Code_Point property (available via ICU).

      Since:
      19.0 (since 1.0 as constant INVISIBLE)
    • singleWidth

      @Deprecated public static CharMatcher singleWidth()
      Deprecated.
      Many such characters are supplementary characters; see the class documentation.
      Determines whether a character is single-width (not double-width). When in doubt, this matcher errs on the side of returning false (that is, it tends to assume a character is double-width).

      Note: as the reference file evolves, we will modify this matcher to keep it up to date.

      See also UAX #11 East Asian Width.

      Since:
      19.0 (since 1.0 as constant SINGLE_WIDTH)
    • is

      public static CharMatcher is(char match)
      Returns a char matcher that matches only one specified BMP character.
    • isNot

      public static CharMatcher isNot(char match)
      Returns a char matcher that matches any character except the BMP character specified.

      To negate another CharMatcher, use negate().

    • anyOf

      public static CharMatcher anyOf(CharSequence sequence)
      Returns a char matcher that matches any BMP character present in the given character sequence. Returns a bogus matcher if the sequence contains supplementary characters.
    • noneOf

      public static CharMatcher noneOf(CharSequence sequence)
      Returns a char matcher that matches any BMP character not present in the given character sequence. Returns a bogus matcher if the sequence contains supplementary characters.
    • inRange

      public static CharMatcher inRange(char startInclusive, char endInclusive)
      Returns a char matcher that matches any character in a given BMP range (both endpoints are inclusive). For example, to match any lowercase letter of the English alphabet, use CharMatcher.inRange('a', 'z').
      Throws:
      IllegalArgumentException - if endInclusive < startInclusive
    • forPredicate

      public static CharMatcher forPredicate(Predicate<? super Character> predicate)
      Returns a matcher with identical behavior to the given Character-based predicate, but which operates on primitive char instances instead.
    • matches

      public abstract boolean matches(char c)
      Determines a true or false value for the given character.
    • negate

      public CharMatcher negate()
      Returns a matcher that matches any character not matched by this matcher.
      Specified by:
      negate in interface Predicate<Character>
    • and

      public CharMatcher and(CharMatcher other)
      Returns a matcher that matches any character matched by both this matcher and other.
    • or

      public CharMatcher or(CharMatcher other)
      Returns a matcher that matches any character matched by either this matcher or other.
    • precomputed

      public CharMatcher precomputed()
      Returns a char matcher functionally equivalent to this one, but which may be faster to query than the original; your mileage may vary. Precomputation takes time and is likely to be worthwhile only if the precomputed matcher is queried many thousands of times.

      This method has no effect (returns this) when called in GWT: it's unclear whether a precomputed matcher is faster, but it certainly consumes more memory, which doesn't seem like a worthwhile tradeoff in a browser.

    • precomputedInternal

      CharMatcher precomputedInternal()
      This is the actual implementation of precomputed(), but we bounce calls through a method on Platform so that we can have different behavior in GWT.

      This implementation tries to be smart in a number of ways. It recognizes cases where the negation is cheaper to precompute than the matcher itself; it tries to build small hash tables for matchers that only match a few characters, and so on. In the worst-case scenario, it constructs an eight-kilobyte bit array and queries that. In many situations this produces a matcher which is faster to query than the original.

    • precomputedPositive

      private static CharMatcher precomputedPositive(int totalCharacters, BitSet table, String description)
      Helper method for precomputedInternal() that doesn't test if the negation is cheaper.
    • isSmall

      private static boolean isSmall(int totalCharacters, int tableLength)
    • setBits

      void setBits(BitSet table)
      Sets bits in table matched by this matcher.
    • matchesAnyOf

      public boolean matchesAnyOf(CharSequence sequence)
      Returns true if a character sequence contains at least one matching BMP character. Equivalent to !matchesNoneOf(sequence).

      The default implementation iterates over the sequence, invoking matches(char) for each character, until this returns true or the end is reached.

      Parameters:
      sequence - the character sequence to examine, possibly empty
      Returns:
      true if this matcher matches at least one character in the sequence
      Since:
      8.0
    • matchesAllOf

      public boolean matchesAllOf(CharSequence sequence)
      Returns true if a character sequence contains only matching BMP characters.

      The default implementation iterates over the sequence, invoking matches(char) for each character, until this returns false or the end is reached.

      Parameters:
      sequence - the character sequence to examine, possibly empty
      Returns:
      true if this matcher matches every character in the sequence, including when the sequence is empty
    • matchesNoneOf

      public boolean matchesNoneOf(CharSequence sequence)
      Returns true if a character sequence contains no matching BMP characters. Equivalent to !matchesAnyOf(sequence).

      The default implementation iterates over the sequence, invoking matches(char) for each character, until this returns true or the end is reached.

      Parameters:
      sequence - the character sequence to examine, possibly empty
      Returns:
      true if this matcher matches no characters in the sequence, including when the sequence is empty
    • indexIn

      public int indexIn(CharSequence sequence)
      Returns the index of the first matching BMP character in a character sequence, or -1 if no matching character is present.

      The default implementation iterates over the sequence in forward order calling matches(char) for each character.

      Parameters:
      sequence - the character sequence to examine from the beginning
      Returns:
      an index, or -1 if no character matches
    • indexIn

      public int indexIn(CharSequence sequence, int start)
      Returns the index of the first matching BMP character in a character sequence, starting from a given position, or -1 if no character matches after that position.

      The default implementation iterates over the sequence in forward order, beginning at start, calling matches(char) for each character.

      Parameters:
      sequence - the character sequence to examine
      start - the first index to examine; must be nonnegative and no greater than sequence.length()
      Returns:
      the index of the first matching character, guaranteed to be no less than start, or -1 if no character matches
      Throws:
      IndexOutOfBoundsException - if start is negative or greater than sequence.length()
    • lastIndexIn

      public int lastIndexIn(CharSequence sequence)
      Returns the index of the last matching BMP character in a character sequence, or -1 if no matching character is present.

      The default implementation iterates over the sequence in reverse order calling matches(char) for each character.

      Parameters:
      sequence - the character sequence to examine from the end
      Returns:
      an index, or -1 if no character matches
    • countIn

      public int countIn(CharSequence sequence)
      Returns the number of matching chars found in a character sequence.

      Counts 2 per supplementary character, such as for whitespace()().negate()().

    • removeFrom

      public String removeFrom(CharSequence sequence)
      Returns a string containing all non-matching characters of a character sequence, in order. For example:
      
       CharMatcher.is('a').removeFrom("bazaar")
       
      ... returns "bzr".
    • retainFrom

      public String retainFrom(CharSequence sequence)
      Returns a string containing all matching BMP characters of a character sequence, in order. For example:
      
       CharMatcher.is('a').retainFrom("bazaar")
       
      ... returns "aaa".
    • replaceFrom

      public String replaceFrom(CharSequence sequence, char replacement)
      Returns a string copy of the input character sequence, with each matching BMP character replaced by a given replacement character. For example:
      
       CharMatcher.is('a').replaceFrom("radar", 'o')
       
      ... returns "rodor".

      The default implementation uses indexIn(CharSequence) to find the first matching character, then iterates the remainder of the sequence calling matches(char) for each character.

      Parameters:
      sequence - the character sequence to replace matching characters in
      replacement - the character to append to the result string in place of each matching character in sequence
      Returns:
      the new string
    • replaceFrom

      public String replaceFrom(CharSequence sequence, CharSequence replacement)
      Returns a string copy of the input character sequence, with each matching BMP character replaced by a given replacement sequence. For example:
      
       CharMatcher.is('a').replaceFrom("yaha", "oo")
       
      ... returns "yoohoo".

      Note: If the replacement is a fixed string with only one character, you are better off calling replaceFrom(CharSequence, char) directly.

      Parameters:
      sequence - the character sequence to replace matching characters in
      replacement - the characters to append to the result string in place of each matching character in sequence
      Returns:
      the new string
    • trimFrom

      public String trimFrom(CharSequence sequence)
      Returns a substring of the input character sequence that omits all matching BMP characters from the beginning and from the end of the string. For example:
      
       CharMatcher.anyOf("ab").trimFrom("abacatbab")
       
      ... returns "cat".

      Note that:

      
       CharMatcher.inRange('\0', ' ').trimFrom(str)
       
      ... is equivalent to String.trim().
    • trimLeadingFrom

      public String trimLeadingFrom(CharSequence sequence)
      Returns a substring of the input character sequence that omits all matching BMP characters from the beginning of the string. For example:
      
       CharMatcher.anyOf("ab").trimLeadingFrom("abacatbab")
       
      ... returns "catbab".
    • trimTrailingFrom

      public String trimTrailingFrom(CharSequence sequence)
      Returns a substring of the input character sequence that omits all matching BMP characters from the end of the string. For example:
      
       CharMatcher.anyOf("ab").trimTrailingFrom("abacatbab")
       
      ... returns "abacat".
    • collapseFrom

      public String collapseFrom(CharSequence sequence, char replacement)
      Returns a string copy of the input character sequence, with each group of consecutive matching BMP characters replaced by a single replacement character. For example:
      
       CharMatcher.anyOf("eko").collapseFrom("bookkeeper", '-')
       
      ... returns "b-p-r".

      The default implementation uses indexIn(CharSequence) to find the first matching character, then iterates the remainder of the sequence calling matches(char) for each character.

      Parameters:
      sequence - the character sequence to replace matching groups of characters in
      replacement - the character to append to the result string in place of each group of matching characters in sequence
      Returns:
      the new string
    • trimAndCollapseFrom

      public String trimAndCollapseFrom(CharSequence sequence, char replacement)
      Collapses groups of matching characters exactly as collapseFrom(java.lang.CharSequence, char) does, except that groups of matching BMP characters at the start or end of the sequence are removed without replacement.
    • finishCollapseFrom

      private String finishCollapseFrom(CharSequence sequence, int start, int end, char replacement, StringBuilder builder, boolean inMatchingGroup)
    • apply

      @Deprecated public boolean apply(Character character)
      Deprecated.
      Provided only to satisfy the Predicate interface; use matches(char) instead.
      Description copied from interface: Predicate
      Returns the result of applying this predicate to input (Java 8+ users, see notes in the class documentation above). This method is generally expected, but not absolutely required, to have the following properties:
      • Its execution does not cause any observable side effects.
      • The computation is consistent with equals; that is, Objects.equal(a, b) implies that predicate.apply(a) == predicate.apply(b)).
      Specified by:
      apply in interface Predicate<Character>
    • toString

      public String toString()
      Returns a string representation of this CharMatcher, such as CharMatcher.or(WHITESPACE, JAVA_DIGIT).
      Overrides:
      toString in class Object
    • showCharacter

      private static String showCharacter(char c)
      Returns the Java Unicode escape sequence for the given char, in the form "ካ" where "12AB" is the four hexadecimal digits representing the 16-bit code unit.
    • isEither

      private static CharMatcher.IsEither isEither(char c1, char c2)