Result of Replace function isn´t used / cannot be applied

Question

I want to iterate over two input strings that being stored in an array. Next, I want to replace all umlauts (ä,ö,ü, ...) by its "aquivalents" a,o,u. Somehow the changes seem to not be applied to the array. How´s that possible and what to do in order to fix this? Thaanks for helping me!!!

        String[] liste = {wort1, wort2};
        for(int i =0; i<2; i++) {
            for (int j=0; j<liste[i].length(); j++) {
                String buchstabe = liste[i].substring(j,j+1);
                switch(buchstabe) {
                    case "ä":
                    case "Ä":
                        buchstabe.replace("ä", "a");
                        break;
                    case "ö":
                    case "Ö":
                        buchstabe.replace("ö", "o");
                        break;
                    case "ü":
                    case "Ü":
                        buchstabe.replace("ü", "u");
                        break;
                    case "ß":
                        buchstabe.replace("ß", "ss");
                        break;
                    default:
                        break;

Answer 1

Strings in are immutable in Java, so you can't change a string. The replace method creates a new strings and returns it, so you'll need to set the buchstabe variable to the newly created string:

buchstabe = buchstabe.replace("ä", "a");

BTW.: You don't need to go through each character individually, the replace method replaces all occurrences in a string.

The replace method does not care whether the needle is present in your haystack. Therefore you can also save the checks whether e.g. an "ä" is contained in your string:

String[] liste = {wort1, wort2};
for(int i = 0; i < liste.length; i++) {
    liste[i] = liste[i].replace("ä", "a");
}