Class AvoidEscapedUnicodeCharactersCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public class AvoidEscapedUnicodeCharactersCheck
    extends AbstractCheck

    Restricts using Unicode escapes (such as \u221e). It is possible to allow using escapes for non-printable, control characters. Also, this check can be configured to allow using escapes if trail comment is present. By the option it is possible to allow using escapes if literal contains only them.

    • Property allowEscapesForControlCharacters - Allow use escapes for non-printable, control characters. Type is boolean. Default value is false.
    • Property allowByTailComment - Allow use escapes if trail comment is present. Type is boolean. Default value is false.
    • Property allowIfAllCharactersEscaped - Allow if all characters in literal are escaped. Type is boolean. Default value is false.
    • Property allowNonPrintableEscapes - Allow use escapes for non-printable, whitespace characters. Type is boolean. Default value is false.

    To configure the check:

     <module name="AvoidEscapedUnicodeCharacters"/>
     

    Examples of using Unicode:

     String unitAbbrev = "μs";     // OK, perfectly clear even without a comment.
     String unitAbbrev = "\u03bcs";// violation, the reader has no idea what this is.
     return '\ufeff' + content;    // OK, an example of non-printable,
                                   // control characters (byte order mark).
     

    An example of how to configure the check to allow using escapes for non-printable, control characters:

     <module name="AvoidEscapedUnicodeCharacters">
       <property name="allowEscapesForControlCharacters" value="true"/>
     </module>
     

    Example of using escapes for non-printable, control characters:

     String unitAbbrev = "μs";      // OK, a normal String
     String unitAbbrev = "\u03bcs"; // violation, "\u03bcs" is a printable character.
     return '\ufeff' + content;     // OK, non-printable control character.
     

    An example of how to configure the check to allow using escapes if trail comment is present:

     <module name="AvoidEscapedUnicodeCharacters">
       <property name="allowByTailComment" value="true"/>
     </module>
     

    Example of using escapes if trail comment is present:

     String unitAbbrev = "μs";      // OK, a normal String
     String unitAbbrev = "\u03bcs"; // OK, Greek letter mu, "s"
     return '\ufeff' + content;
     // -----^--------------------- violation, comment is not used within same line.
     

    An example of how to configure the check to allow if all characters in literal are escaped.

     <module name="AvoidEscapedUnicodeCharacters">
       <property name="allowIfAllCharactersEscaped" value="true"/>
     </module>
     

    Example of using escapes if all characters in literal are escaped:

     String unitAbbrev = "μs";      // OK, a normal String
     String unitAbbrev = "\u03bcs"; // violation, not all characters are escaped ('s').
     String unitAbbrev = "\u03bc\u03bc\u03bc"; // OK
     String unitAbbrev = "\u03bc\u03bcs";// violation, not all characters are escaped ('s').
     return '\ufeff' + content;          // OK, all control characters are escaped
     

    An example of how to configure the check to allow using escapes for non-printable whitespace characters:

     <module name="AvoidEscapedUnicodeCharacters">
       <property name="allowNonPrintableEscapes" value="true"/>
     </module>
     

    Example of using escapes for non-printable whitespace characters:

     String unitAbbrev = "μs";       // OK, a normal String
     String unitAbbrev1 = "\u03bcs"; // violation, printable escape character.
     String unitAbbrev2 = "\u03bc\u03bc\u03bc"; // violation, printable escape character.
     String unitAbbrev3 = "\u03bc\u03bcs";// violation, printable escape character.
     return '\ufeff' + content;           // OK, non-printable escape character.
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • forbid.escaped.unicode.char
    Since:
    5.8
    • Method Detail

      • setAllowEscapesForControlCharacters

        public final void setAllowEscapesForControlCharacters​(boolean allow)
        Setter to allow use escapes for non-printable, control characters.
        Parameters:
        allow - user's value.
      • setAllowByTailComment

        public final void setAllowByTailComment​(boolean allow)
        Setter to allow use escapes if trail comment is present.
        Parameters:
        allow - user's value.
      • setAllowIfAllCharactersEscaped

        public final void setAllowIfAllCharactersEscaped​(boolean allow)
        Setter to allow if all characters in literal are escaped.
        Parameters:
        allow - user's value.
      • setAllowNonPrintableEscapes

        public final void setAllowNonPrintableEscapes​(boolean allow)
        Setter to allow use escapes for non-printable, whitespace characters.
        Parameters:
        allow - user's value.
      • getAcceptableTokens

        public int[] getAcceptableTokens()
        Description copied from class: AbstractCheck
        The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
        Specified by:
        getAcceptableTokens in class AbstractCheck
        Returns:
        the token set this check is designed for.
        See Also:
        TokenTypes
      • beginTree

        public void beginTree​(DetailAST rootAST)
        Description copied from class: AbstractCheck
        Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.
        Overrides:
        beginTree in class AbstractCheck
        Parameters:
        rootAST - the root of the tree
      • hasUnicodeChar

        private static boolean hasUnicodeChar​(String literal)
        Checks if literal has Unicode chars.
        Parameters:
        literal - String literal.
        Returns:
        true if literal has Unicode chars.
      • isOnlyUnicodeValidChars

        private static boolean isOnlyUnicodeValidChars​(String literal,
                                                       Pattern pattern)
        Check if String literal contains Unicode control chars.
        Parameters:
        literal - String literal.
        pattern - RegExp for valid characters.
        Returns:
        true, if String literal contains Unicode control chars.
      • hasTrailComment

        private boolean hasTrailComment​(DetailAST ast)
        Check if trail comment is present after ast token.
        Parameters:
        ast - current token.
        Returns:
        true if trail comment is present after ast token.
      • isTrailingBlockComment

        private static boolean isTrailingBlockComment​(TextBlock comment,
                                                      int... codePoints)
        Whether the C style comment is trailing.
        Parameters:
        comment - the comment to check.
        codePoints - the first line of the comment, in unicode code points
        Returns:
        true if the comment is trailing.
      • countMatches

        private static int countMatches​(Pattern pattern,
                                        String target)
        Count regexp matches into String literal.
        Parameters:
        pattern - pattern.
        target - String literal.
        Returns:
        count of regexp matches.
      • isAllCharactersEscaped

        private boolean isAllCharactersEscaped​(String literal)
        Checks if all characters in String literal is escaped.
        Parameters:
        literal - current literal.
        Returns:
        true if all characters in String literal is escaped.