groovy regex, how to match array items in a string

Question

The string looks like this "[xx],[xx],[xx]" Where xx is a ploygon like this "(1.0,2.3),(2.0,3)...

Basically, we are looking for a way to get the string between each pair of square brackets into an array.

E.g. String source = "[hello],[1,2],[(1,2),(2,4)]"

would result in an object a such that:

a[0] == 'hello'
a[1] == '1,2'
a[2] == '(1,2),(2,4)'

We have tried various strategies, including using groovy regex:

def p = "[12],[34]"
def points = p =~ /(\[([^\[]*)\])*/
println points[0][2] // yields 12

However,this yields the following 2 dim array:

[[12], [12], 12]
[, null, null]
[[34], [34], 34]

so if we took the 3rd item from every even rows we would be ok, but this does look very correct. We are not talking into account the ',' and we are not sure why we are getting "[12]" twice, when it should be zero times?

Any regex experts out there?

Your regex can match an empty string (thus, you have nulls and 3 matches) and the regex has 2 capturing groups (thus, you have 3 groups all in all - thus, you have 3 elements in each match). You must be looking for \[([^\[]*)], right? Or do you want to just get rid of a capturing group altogether with (?<=\[)[^\[\]]* — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Oct 27, 2015 at 12:20
You can try: (source =~ /(?:\[([^\]]*)\])*/)*.getAt(1).findAll() — tim_yates
– tim_yates, Commented Oct 27, 2015 at 12:35
(source =~ /(?:[([^]]*)])*/)*.getAt(1).findAll() works! Many thanks! Not sure what its doing though, what does the colon do? — John Little
– John Little, Commented Oct 27, 2015 at 12:51

albciff · Accepted Answer · 2015-10-27 12:54:57Z

1

I think that this is what you're looking for:

def p = "[hello],[1,2],[(1,2),(2,4)]"
def points = p.findAll(/\[(.*?)\]/){match, group -> group }
println points[0]
println points[1]
println points[2]

This scripts prints:

hello
1,2
(1,2),(2,4)

The key is the use of the .*? to make the expression non-greedy to found the minimum between chars [] to avoid that the first [ match with the last ] resulting match in hello],[1,2],[(1,2),(2,4) match... then with findAll you returns only the group captured.

Hope it helps,

edited Oct 27, 2015 at 12:54

answered Oct 27, 2015 at 12:49

albciff

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