Why is the star quantifier greedier than the plus quantifier in Java regular expressions?
java, regex, regex-greedy
Solution
It's not a difference in greediness. In your first regex:
.*([A-Za-z]+)>([A-Za-z]+)<.*
You are asking for any amount of characters (`.*`), then at least a letter, then a `>`. So the greedy match has to be D, since `*` consumes everything before D.
In the second one, instead:
.*([A-Za-z]*)>([A-Za-z]+)<.*
You want any amount of characters, followed by any amount of letters, then the `>`. So the first * consumes everything up to the `>`, and the first capture group matches an empty string. I don't think that it "matches perfectly" at all.
Problem
I have text I'm trying to extract from `LogicalID` and `SupplyChain` from ``` <LogicalID>SupplyChain</Logical> ``` At first I used the following regex: ``` .*([A-Za-z]+)>([A-Za-z]+)<.* ``` This matched as follows: ``` ["D", "SupplyChain"] ``` In a fit of desperation, I tried using the asterisk instead of the plus: ``` .*([A-Za-z]*)>([A-Za-z]+)<.* ``` This matched perfectly. The documentation says `*` matches zero or more times and `+` matches one or more times. Why is `*` greedier than `+`? EDIT: It's been pointed out to me that this isn't the case below. The order of operations explains why the first match group is actually null.