Question

I have a String like – "Bangalore,India=Karnataka". From this String I would like to extract only the substring "Bangalore". In this case the regex can be – (.+),.*=.*. But the problem is, the String can sometimes come like only "Bangalore". Then in that case the above regex wont work. What will be the regex to get the substring "Bangalore" whatever the String be ?

Answer 1

Try this one:

^(.+?)(?:,.*?)?=.*$

Explanation:

^               # Begining of the string
  (             # begining of capture group 1
    .+?         # one or more any char non-greedy
  )             # end of group 1
  (?:           # beginig of NON capture group
    ,           # a comma
    .*?         # 0 or more any char non-greedy
  )?            # end of non capture group, optional
  =             # equal sign
  .*            # 0 or more any char
$               # end of string

Updated:
I thougth OP have to match Bangalore,India=Karnataka or Bangalore=Karnataka but as farr as I understand it is Bangalore,India=Karnataka or Bangalore so the regex is much more simpler :

^([^,]+)

This will match, at the begining of the string, one or more non-comma character and capture them in group 1.