Suppose we want to search the word Hello for only two times side by side in a line and we write a regex (?:Hello){2} Now…

When we search a pattern one or more time we use ‘*’. But Sometime we want to search a character or a pattern for a…

(?<!…) is used to checks if any preceding character or pattern does not match the specified pattern.Syntax: (?<!preceedingPattern)patternLet’s see with example: We have some lines…

Suppose we have some lines below from where we just want to cut out ‘hello’ regardless of its case.Lines: fetch hello onlynot hello-worldavailable hellonot the…

\1 refers to the first capturing group. \2 refers to the second capturing group.\2 refers to the third capturing group.. . . Let’s understand more…

In regular expression (?=…) is a positive lookahead. It checks if the pattern is matched at the current position, but does not include it in…

Capturing and non-capturing groups are used to group a pattern. In simple words we can treat a set of characters( Eg. [a-zA-Z0-9] and also other…

We can use a \s to search empty string, spaces, new lines etc.Regular expression will be : ^\s*$ Explanation of the regex : ^ :…