java - Regex that matches only one occurrence -

i'm wanting replace occurrences of "=" "==" in string regex, there single occurrence of "=".

basically want transform:

where = b | c == d 

into

where == b | c == d 

what i'm struggling finding 1 occurrence. i've tried [^=]=[^=], matching characters on either side too.

you can try using lookarounds:

(?<!=)=(?!=) 

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using example:

system.out.println("where = b | c == d".replaceall("(?<!=)=(?!=)", "==")); 

 == b | c == d