How do I use the IsAlphabetic binary property in a Java regex match?

Question

I'm using this pattern to check if a string starts with at least 2 alphabetic characters in front a colon:

string.matches("^\\p{IsAlphabetic}{2,}:")

but I get the following exception thrown at me:

java.util.regex.PatternSyntaxException: Unknown character property name {Alphabetic} near index 16
    ^\p{IsAlphabetic}{2,}:
    ^
    at java.util.regex.Pattern.error(Pattern.java:1730)
    at java.util.regex.Pattern.charPropertyNodeFor(Pattern.java:2454)
    at java.util.regex.Pattern.family(Pattern.java:2429)
    at java.util.regex.Pattern.sequence(Pattern.java:1848)
    at java.util.regex.Pattern.expr(Pattern.java:1769)
    at java.util.regex.Pattern.compile(Pattern.java:1477)
    at java.util.regex.Pattern.<init>(Pattern.java:1150)
    at java.util.regex.Pattern.compile(Pattern.java:840)
    at java.util.regex.Pattern.matches(Pattern.java:945)
    at java.lang.String.matches(String.java:2102)

even though the specification of the Pattern classes states:

Binary properties are specified with the prefix Is, as in IsAlphabetic. The supported binary properties by Pattern are

Alphabetic

Ideographic

Letter

...

and the section Classes for Unicode scripts, blocks, categories and binary properties lists

\p{IsAlphabetic} An alphabetic character (binary property)

it works for me. Note that matches method tries to match the whole string. — Avinash Raj
– Avinash Raj, Commented Apr 18, 2015 at 14:35
It doesn't matter if I enclose \\p{IsAlphabetic} in a character class with []. — freedio
– freedio, Commented Apr 18, 2015 at 14:36
Your pattern works correctly in this online tester: regexplanet.com/advanced/java/index.html. — John Bollinger
– John Bollinger, Commented Apr 18, 2015 at 14:39

laune · Accepted Answer · 2015-04-18 14:58:46Z

3

Works and returns true using java 1.8.

String s = "äö:";
System.out.println(s.matches("^\\p{IsAlphanumeric}{2,}:"));

Note that the forms available in Java 1.7 - Alpha, IsAlpha - do not necessarily include characters not in US-ASCII . This returns false:

String s = "äö:";
System.out.println(s.matches("^\\p{IsAlpha}{2,}:"));

But note that this works in 1.7 and returns true:

String s = "äö:";
Pattern pat = Pattern.compile( "^\\p{Alpha}{2,}:",
                     Pattern.UNICODE_CHARACTER_CLASS );
Matcher mat = pat.matcher( s );
System.out.println(mat.matches());

edited Apr 18, 2015 at 14:58

answered Apr 18, 2015 at 14:53

laune

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1 Comment

John Bollinger Over a year ago

The form with \p{Alpha} (but not the one with \p{IsAlpha}) does work if the UNICODE_CHARACTER_CLASS flag is specified for the pattern, as documented. Tested on Java 8 against the input given in this answer.

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