A word that is combined Chinese characters with alpha digits characters seems like a whole word. So \b is no use on matching the alpha digits characters in the word.
// your code goes here
Pattern with_word_boundary = Pattern.compile("(?i)^\\w+\\b.*$");
Pattern without_word_boundary = Pattern.compile("(?i)^\\w+.*$");
String case_1 = "China中国";
String case_2 = "China 中国";
System.out.println(with_word_boundary.matcher(case_1).matches()); // false
System.out.println(with_word_boundary.matcher(case_2).matches()); // true
System.out.println(without_word_boundary.matcher(case_1).matches()); // true
System.out.println(without_word_boundary.matcher(case_2).matches()); // true