Convert Unicode to ASCII without changing the string length (in Java)

Question

What is the best way to convert a string from Unicode to ASCII without changing it\'s length (that is very important in my case)? Also the characters without any conversion

Answer 1

As stated in this answer, the following code should work:

    String s = "口水雞 hello Ä";

    String s1 = Normalizer.normalize(s, Normalizer.Form.NFKD);
    String regex = "[\\p{InCombiningDiacriticalMarks}\\p{IsLm}\\p{IsSk}]+";

    String s2 = new String(s1.replaceAll(regex, "").getBytes("ascii"), "ascii");

    System.out.println(s2);
    System.out.println(s.length() == s2.length());

Output is

??? hello A
true

So you first remove diactrical marks, the convert to ascii. Non-ascii characters will become question marks.