Multiple regex for replacing characters in java

Question

I have the following string:

String str = "Klaße, STRAßE, FUß";

Using of combined regex I want to replace German ß letter to ss or SS respectively. To perform this I have:

String replaceUml = str
        .replaceAll("ß", "ss")
        .replaceAll("A-Z|ss$", "SS")
        .replaceAll("^(?=^A-Z)(?=.*A-Z$)(?=.*ss).*$", "SS");

Expected result:

Klasse, STRASSE, FUSS

Actual result:

Klasse, STRAssE, FUSS

Where I'm wrong?

Answer 1

String replaceUml = str
    .replaceAll("(?<=\\p{Lu})ß", "SS")
    .replace("ß", "ss")

This uses regex with a preceding unicode upper case letter ("SÜß"), to have capital "SS".

The (?<= ... ) is a look-behind, a kind of context matching. You could also do

    .replaceAll("(\\p{Lu})ß", "$1SS")

as ß will not occure at the beginning.

Your main trouble was not using brackets [A-Z].