Replace character if not preceeded by "+"

Question

in java i need to replace a number with a word only if it is not preceeded by the "+". Example:

- match1
- match+1

Should become:

matchone
match+1 (no modify)

I tried with

>>>name = name.replaceAll("([^+])1", "one");
matcone                                      //required "matchone"

But it is not working. Any suggestions?

Thank you

Is the requirement to replace only number '1'? Your question does not specify but your regex suggests otherwise. — Kaushik NP, Sep 18 '17 at 07:58
You need to specify what you mean with "But it is not working". What is the output you're getting, and what is the output that you expected? — Erwin Bolwidt, Sep 18 '17 at 08:02
See [regex for matching something if it is not preceded by something else](https://stackoverflow.com/questions/9306202/regex-for-matching-something-if-it-is-not-preceded-by-something-else). — Wiktor Stribiżew, Sep 18 '17 at 08:07

score 5 · Accepted Answer · edited Sep 18 '17 at 08:04

5

Use a negative lookbehind:

name = name.replaceAll("(?<!\\+)1", "one");

edited Sep 18 '17 at 08:04

YCF_L

answered Sep 18 '17 at 08:02

Toto

You mean: "look-behind" – laune Sep 18 '17 at 08:04
This gives an "Illegal escape character in string literal" :-( – Pecana Sep 18 '17 at 08:04
2

@YCF_L: Thanks for edit. I always forget double escaping :-( – Toto Sep 18 '17 at 08:07

score 1 · Answer 2 · answered Sep 18 '17 at 08:05

Your regex is eating the character before the one and replacing that with "one" as well, so the output in the first instance is "matcone".

You can use a negative look-behind expression (?<!) to match any "1" that is not preceded by a "+":

name = name.replaceAll("(?<!\\+)1", "one");

2 Answers2