Class CharMatcher

java.lang.Object
com.google.common.base.CharMatcher
All Implemented Interfaces:
Predicate<Character>

@GwtCompatible(emulated=true) 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; it does not understand supplementary Unicode code points in the range 0x10000 to 0x10FFFF. Such logical characters are encoded into a String using surrogate pairs, and a CharMatcher treats these just as two separate characters.

Example usages:

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

See the Guava User Guide article on CharMatcher .

Since:
1.0
  • Field Details

    • WHITESPACE

      @Deprecated public static final CharMatcher WHITESPACE
      Deprecated.
      Use whitespace() instead. This constant is scheduled to be removed in June 2018.
      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".)

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

    • BREAKING_WHITESPACE

      @Deprecated public static final CharMatcher BREAKING_WHITESPACE
      Deprecated.
      Use breakingWhitespace() instead. This constant is scheduled to be removed in June 2018.
      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:
      2.0
    • ASCII

      @Deprecated public static final CharMatcher ASCII
      Deprecated.
      Use ascii() instead. This constant is scheduled to be removed in June 2018.
      Determines whether a character is ASCII, meaning that its code point is less than 128.
    • DIGIT

      @Deprecated public static final CharMatcher DIGIT
      Deprecated.
      Use digit() instead. This constant is scheduled to be removed in June 2018.
      Determines whether a character is a digit according to Unicode. If you only care to match ASCII digits, you can use inRange('0', '9').
    • JAVA_DIGIT

      @Deprecated public static final CharMatcher JAVA_DIGIT
      Deprecated.
      Use javaDigit() instead. This constant is scheduled to be removed in June 2018.
      Determines whether a character is a digit according to Java's definition. If you only care to match ASCII digits, you can use inRange('0', '9').
    • JAVA_LETTER

      @Deprecated public static final CharMatcher JAVA_LETTER
      Deprecated.
      Use javaLetter() instead. This constant is scheduled to be removed in June 2018.
      Determines whether a character is a 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')).
    • JAVA_LETTER_OR_DIGIT

      @Deprecated public static final CharMatcher JAVA_LETTER_OR_DIGIT
      Deprecated.
      Use javaLetterOrDigit() instead. This constant is scheduled to be removed in June 2018.
      Determines whether a character is a letter or digit according to Java's definition.
    • JAVA_UPPER_CASE

      @Deprecated public static final CharMatcher JAVA_UPPER_CASE
      Deprecated.
      Use javaUpperCase() instead. This constant is scheduled to be removed in June 2018.
      Determines whether a character is upper case according to Java's definition.
    • JAVA_LOWER_CASE

      @Deprecated public static final CharMatcher JAVA_LOWER_CASE
      Deprecated.
      Use javaLowerCase() instead. This constant is scheduled to be removed in June 2018.
      Determines whether a character is lower case according to Java's definition.
    • JAVA_ISO_CONTROL

      @Deprecated public static final CharMatcher JAVA_ISO_CONTROL
      Deprecated.
      Use javaIsoControl() instead. This constant is scheduled to be removed in June 2018.
      Determines whether a character is an ISO control character as specified by Character.isISOControl(char).
    • INVISIBLE

      @Deprecated public static final CharMatcher INVISIBLE
      Deprecated.
      Use invisible() instead. This constant is scheduled to be removed in June 2018.
      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.
    • SINGLE_WIDTH

      @Deprecated public static final CharMatcher SINGLE_WIDTH
      Deprecated.
      Use singleWidth() instead. This constant is scheduled to be removed in June 2018.
      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 constant to keep it up to date.

    • ANY

      @Deprecated public static final CharMatcher ANY
      Deprecated.
      Use any() instead. This constant is scheduled to be removed in June 2018.
      Matches any character.
    • NONE

      @Deprecated public static final CharMatcher NONE
      Deprecated.
      Use none() instead. This constant is scheduled to be removed in June 2018.
      Matches no characters.
  • 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".)

      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

      public static CharMatcher digit()
      Determines whether a character is a 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

      public static CharMatcher javaDigit()
      Determines whether a character is a 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

      public static CharMatcher javaLetter()
      Determines whether a character is a 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

      public static CharMatcher javaLetterOrDigit()
      Determines whether a character is a letter or digit according to Java's definition.
      Since:
      19.0 (since 1.0 as constant JAVA_LETTER_OR_DIGIT).
    • javaUpperCase

      public static CharMatcher javaUpperCase()
      Determines whether a character is upper case according to Java's definition.
      Since:
      19.0 (since 1.0 as constant JAVA_UPPER_CASE)
    • javaLowerCase

      public static CharMatcher javaLowerCase()
      Determines whether a 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).
      Since:
      19.0 (since 1.0 as constant JAVA_ISO_CONTROL)
    • invisible

      public static CharMatcher invisible()
      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.
      Since:
      19.0 (since 1.0 as constant INVISIBLE)
    • singleWidth

      public static CharMatcher singleWidth()
      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.

      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 character.
    • isNot

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

      To negate another CharMatcher, use negate().

    • anyOf

      public static CharMatcher anyOf(CharSequence sequence)
      Returns a char matcher that matches any character present in the given character sequence.
    • noneOf

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

      public static CharMatcher inRange(char startInclusive, char endInclusive)
      Returns a char matcher that matches any character in a given 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.
    • 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.

    • matchesAnyOf

      public boolean matchesAnyOf(CharSequence sequence)
      Returns true if a character sequence contains at least one matching 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 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 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 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 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 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 characters found in a character sequence.
    • 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 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 character that matches this matcher 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 character that matches this matcher 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 characters this matcher matches 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 characters this matcher matches 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 characters this matcher matches 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 characters that match this matcher 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 characters at the start or end of the sequence are removed without replacement.
    • 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