How Can I Improve Unicode Support in Java Regular Expressions for \w and \b?

Unicode Equivalents for w and b in Java Regular Expressions

Java's regex implementation has limited support for Unicode, making it challenging to match words or word boundaries accurately. The default w and b escapes correspond only to ASCII characters.

To address this issue, consider using a function that rewrites these escapes, replacing them withUnicode-aware definitions. This function can rewrite the following 14 charclass escapes:

\w \W \s \S \v \V \h \H \d \D \b \B \X \R

Rewritten Escape Definitions:

• w: Captures letters, digits, and certain punctuation characters (p{L}pMp{Nd}p{Nl}p{Pc}[p{InEnclosedAlphanumerics}&&p{So}]])
• W: Excludes all characters matched by w
• s: Matches Unicode whitespace ([u0009-u000Du0020u0085u00A0u1680u180Eu2000-u200Au2028u2029u202Fu205Fu3000])
• S: Excludes all characters matched by s
• v: Matches Unicode vertical whitespace ([u000A-u000Du0085u2028u2029])
• V: Excludes all characters matched by v
• h: Matches Unicode horizontal whitespace ([u0009u0020u00A0u1680u180Eu2000-u200Au202Fu205Fu3000])
• H: Excludes all characters matched by h
• d: Matches Unicode digits (p{Nd})
• D: Excludes all characters matched by d
• b: Matches word boundaries considering only Unicode word characters
• B: Matches non-word boundaries considering Unicode word characters
• X: Matches extended grapheme clusters
• R: Matches line breaks, including Unicode line breaks

Boundary Definitions:

Boundary escapes (b and B) can be rewritten using the following logic:

• b: (?:(?<=w)(?!w)|(?
• B: (?:(?<=w)(?=w)|(?

Fixing Java with Java:

This function can be implemented in Java using the code provided in the original discussion thread. By using this code, you can rewrite regex patterns to better handle Unicode characters.

Note:
In Java 7, the Pattern class introduces the UNICODE_CHARACTER_CLASS flag, which enables Unicode support for these escapes by default.

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