replacing mapping character using regex in java [duplicate]

Question

I want to replace all 'A' of a string by 'B', and all 'B' by 'Z' so that the result of "ABCAAB" will be "BZCBBZ".

Is there a way to replace the following code using the replaceAll function?

String init = "ABCAAB"
String res = "";

for (char c: init.toCharArray()){
    switch (c) {
        case 'A':res = res+'B';
        case 'B':res = res+'Z';

        default :res = res+c;

       }
    }

String res = init.replaceAll("B", "Z").replaceAll("A", "B"); — anubhava
– anubhava, Commented Sep 18, 2018 at 9:59
Simpler: String res = init.replace("B", "Z").replace("A", "B"); — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 18, 2018 at 10:01
tricky! but is there possible doing it once (if I had more replacements to do and no order possible to perform them) — jtobelem
– jtobelem, Commented Sep 18, 2018 at 10:01
@WiktorStribiżew I don't think your duplicate is correct, that question is about replacing words in a string, this one is about replacing letters where the replacement of one letter could also be a letter that if it wasn't a replacement character would be being replaced by a third character. — JGNI
– JGNI, Commented Sep 18, 2018 at 10:07
@WiktorStribiżew I may be showing my lack of coffee this morning but I don't see how either solve the a => b, b => c mapping without converting ab to cc. Note that the OP says he could have the following mapping a => b, b => c, c => a which means there is no correct way of ordering replacements. — JGNI
– JGNI, Commented Sep 18, 2018 at 10:21

JGNI · Accepted Answer · 2018-09-18 10:02:27Z

1

If you know that your string is in upper case letters then you can make the replacement characters lower case, thus marking them as changed. This means that you can change A to b and B to z with out changing A to Z. Once all the transformations have been done you can upper case the string.

answered Sep 18, 2018 at 10:02

JGNI

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