FULL PRODUCT VERSION :
java version "1.6.0_07"
Java(TM) SE Runtime Environment (build 1.6.0_07-b06)
Java HotSpot(TM) Client VM (build 10.0-b23, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
ExceptionInInitializerError is caught when the pattern has precomposed characters in CANON_EQ mode.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile and run the program.

ACTUAL -
java.lang.ExceptionInInitializerError
Caused by: java.util.regex.PatternSyntaxException: Unclosed group near index 27
(?:e?e|?e|ee?(?:e?n|?n|en?)
                           ^
at java.util.regex.Pattern.error(Unknown Source)
at java.util.regex.Pattern.accept(Unknown Source)
at java.util.regex.Pattern.group0(Unknown Source)
at java.util.regex.Pattern.sequence(Unknown Source)
at java.util.regex.Pattern.expr(Unknown Source)
at java.util.regex.Pattern.compile(Unknown Source)
at java.util.regex.Pattern.<init>(Unknown Source)
at java.util.regex.Pattern.compile(Unknown Source)
at sample.RegexTest.<clinit>(RegexTest.java:6)

Exception in thread "main"

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package sample;

import java.util.regex.*;

public class RegexTest {
static final Pattern pt = Pattern.compile("één", Pattern.CANON_EQ);

public static void main(String[] args) {
System.out.println(pt.matcher("één").matches());
}
}

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