scala regex get all string matching input

Question

I've below scala function.

def getMatchesFor(input: String, matchId: String): List[String] = {
  val regex = s"""${matchId}_\w*""".r
  (regex findAllIn input).toList
}

What is the expectation of the function is

  val input = "abc_1_1_1_0abc_1_0_1"
  val result = getMatchesFor(input, "abc")

result should be List("abc_1_1_1_0", "abc_1_0_1")

I've tried so far val r = s"${matchId}_\\w*".r but it is not working as expected.

How can I fix this issue?

@LeviRamsey the result should be abc_1_xyz. Please let me know if you have any more questions — user51
– user51, Commented Oct 13, 2022 at 3:38

Moritz · Accepted Answer · 2022-10-13 04:58:39Z

2

Here's a regex that matches your needs:

val regex = s"${matchId}_\\w*?((?=${matchId})|\\W|$$)".r

\w* must be none greedy, otherwise it would just match everything. It should only match until followed by:

the next matchId using a lookahead (?=${matchId})
a non word character \W
or the line end $

An alternative approach might be to simply split the string using matchId and extract the remaining match _\w* from the parts (ignoring the first split).

answered Oct 13, 2022 at 4:58

Moritz

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The fourth bird · Accepted Answer · 2022-10-13 09:02:08Z

1

Another option using split and a positive lookahead.

See the positions for the split.

def getMatchesFor(input: String, matchId: String): List[String] = {
    val regex = s"""(?=${matchId}_)""".r
    regex.split(input).toList
}

Output

List(abc_1_1_1_0, abc_1_0_1)

answered Oct 13, 2022 at 9:02

The fourth bird

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2 Comments

user51 Over a year ago

simple answer. I've already accepted the other one.

The fourth bird Over a year ago

@RajkumarNatarajan That is perfectly ok.

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