Regex to replace a substring in java

Question

I have a list containing strings like below

/b/Xfassds12312/5324234/img1.jpg
/b/asda33CSds/765345/img1.jpg
/b/iop98plkKLJ/2421466/img1.jpg
/b/nzcbWWSJk/3424535/img1.jpg

I need to replace the /b/ to /img/ in every string of that list.

I tried the below pattern.. looks like it appending instead of replacing.. not sure what I'm missing

replaceFirst("(/[^/]*)", "$1" + "img");

Answer 1

If the other strings would not breaks, just use yourString.replace("/b/", "/img/");

Answer 2

Use

String output = yourString.replaceFirst("^/[^/]+", "/img");

See proof .

VISUAL:

EXPLANATION:

NODE                     EXPLANATION
--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  /                        '/'
--------------------------------------------------------------------------------
  [^/]+                    any character except: '/' (1 or more times
                           (matching the most amount possible))