CODEWITHSUNDEEP
javaregex
kumar
kumar

Reputation: 595

Regular expression for a complex string

I am new to regexp. I need to validate a string, but when I use my current attempt it is always returning false.

Rules:

  1. A text matcher like "polygon(( ))"
  2. number matcher like X Y, where x and y can be any double numbers
  3. as many X Y pairs, separated by comma.

eg:

PolyGoN((
-74.0075783459999 40.710775696, 
-74.007375926 40.710655064, 
-74.0074640719999 40.7108592490001, 
-74.0075783459999 40.710775696))

Here is the code that I used:

String inputString = "POLYGON((-74.0075783459999 40.710775696, -74.007375926 40.710655064, -74.0072836009999 40.710720973, -74.0075783459999 40.710775696))";
String regexp = "polygon[\\((][(\\-?\\d+(\\.\\d+)?)\\s*(\\-?\\d+(\\.\\d+)?)]*[\\))]";
Pattern pattern = Pattern.compile(regexp, Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(inputString);
boolean result = matcher.matches();

Upvotes: 0

Views: 894

Answers (2)

Ravi K Thapliyal
Ravi K Thapliyal

Reputation: 51711

[\\((] is incorrect way of specifying that you need ( twice. No matter how many times you repeat a character but inside a character class [] it counts only once. Since, it's the same character repeating you don't even need a character class there but just the character \\( with a quantifier that tells how many times it should repeat {2}. So, you need \\({2} at the start and \\){2} at the end.

Another problem with your use of [] is that you used them to denote a group of double pairs that repeats (using *). You always use () for grouping a part of your match. [] denotes a character class only. I wonder why you got that wrong because you grouped your doubles and their pairs correctly.

Next, you've forgotten to match all the commas , separating the double pairs. I've included that as (,\\s*)? in my regex. The hyphen - (or the negative sign here) doesn't need to be escaped since it's not inside a character class [] and so the regex parser knows you're not using it to specify a character range.

The corrected regex is (indented for clarity)

polygon\({2}\s*(
    (-?\d+(\.\d+)?)\s*(-?\d+(\.\d+)?)(,\s*)
  )*(-?\d+(\.\d+)?)\s*(-?\d+(\.\d+)?)
\s*\){2}

Upvotes: 3

gbtimmon
gbtimmon

Reputation: 4322

m|Polygon\(\(((\s*-?\d+\.\d+\s*){2},)*(\s*-?\d+\.\d+\s*){2}\)\)|i

Upvotes: 0

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