String groupChars;
if (pattern.length() == 0)
throw new ParseException("Build rules empty.", 0);
// This array maps Unicode characters to their collation ordering
mapping = new UCompactIntArray((int)RBCollationTables.UNMAPPED);
// Normalize the build rules. Find occurances of all decomposed characters
// and normalize the rules before feeding into the builder. By "normalize",
// we mean that all precomposed Unicode characters must be converted into
// a base character and one or more combining characters (such as accents).
// When there are multiple combining characters attached to a base character,