FULL PRODUCT VERSION :
$java -version

java version "1.6.0_26"
Java(TM) SE Runtime Environment (build 1.6.0_26-b03)
Java HotSpot(TM) Client VM (build 20.1-b02, mixed mode, sharing)


ADDITIONAL OS VERSION INFORMATION :
$uname -a

Linux lc_rh_8 2.4.27 #3 SMP Fri Oct 31 16:51:51 GMT 2008 i686 i686 i386 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
This problem happens only when the unicode canonical equivalent match enabled (Pattern.CANON_EQ).

It seems to me that the pattern string normalization is not handled correctly. When I add a capturing group (a pair of parentheses) to enclose one unicode string (one base character and followed by the two NON_SPACING_MARK characters), the right parenthesis is somehow treated as the NON_SPACING_MARK character as well.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Use the source code I pasted below:

javac Test.java
java Test abcd

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
it should print "false"

ACTUAL -
an exception was thrown out:

Exception in thread "main" java.util.regex.PatternSyntaxException: Unmatched closing ')' near index 14
a((?:A??)|??)|?)?|A?)?|?)?|??)|A??)|Á?)|??)|?)?|Á)?|A?)?|Á)?|Á?)|??)|?)?|A)??|A)??)
              ^
        at java.util.regex.Pattern.error(Pattern.java:1713)
        at java.util.regex.Pattern.compile(Pattern.java:1464)
        at java.util.regex.Pattern.<init>(Pattern.java:1133)
        at java.util.regex.Pattern.compile(Pattern.java:847)
        at Test.<init>(Test.java:8)
        at Test.main(Test.java:19)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.util.regex.*;

public class Test {
    private Pattern pattern;

    public Test() {
        String patternString = "a(\u0041\u0301\u0328)"; // capture group 1
        pattern = Pattern.compile(patternString, Pattern.CANON_EQ); // unicode canonical equivalent match
    }

    boolean match(String s) {
        Matcher m = pattern.matcher(s);
        return m.find();
    }


    public static void main(String[] argv) {
        if (argv.length > 0) {
            boolean matched = new Test().match(argv[0]);
            System.out.println(matched);
        }
    }
}

---------- END SOURCE ----------