Regex characters:
Meaningful characters:
. can be any character.\ to use the characters themselves and not their regex representation.\d all numbers.\D all characters excepts numbers.\w all English letters, numbers and -.\W !\w.
Counting characters:
+ shows that a character is repeated one or more times.* the previous character is repeated 0 or more times. (like + but the repetition is at least 0)? the previous character is present 0 or 1 time.{} certain number of repetition for a char. like a{3}: aaa. It can also be an interval.
Lookahead
- Positive Lookahead: Checks if after the text there is a certain condition.
something(?=condition)
- Negative Lookahead: the same as the positive but it check if the condition is not met.
something(?!condition)
java