I have trouble splitting string based on regex.
String str = "1=(1-2,3-4),2=2,3=3,4=4";
Pattern commaPattern = Pattern.compile("\\([0-9-]+,[0-9-]+\\)|(,)") ;
String[] arr = commaPattern.split(str);
for (String s : arr)
{
System.out.println(s);
}
Expected output,
1=(1-2,3-4)
2=2
3=3
4=4
Actual output,
1=
2=2
3=3
4=4
This regex would split as required
,(?![^()]*\\))
------------
|->split with , only if it is not within ()
\\) is considered as a part of the Quantifiers instead of a Character? Why ,?!([^()]*\\)) won't work? Thanks!
, is being matched via lookahead. By lookahead, the regex engine wont consume characters, its like a boolean condition, so instead of consuming characters and moving ahead, it will check if the condition is true or not..This is required because if you try to split without lookaheads, it will also split on the matched content other then ,``This isn't well suited for a split(...). Consider scanning through the input and matching instead:
String str = "1=(1-2,3-4),2=2,3=3,4=4";
Matcher m = Pattern.compile("(\\d+)=(\\d+|\\([^)]*\\))").matcher(str);
while(m.find()) {
String key = m.group(1);
String value = m.group(2);
System.out.printf("key=%s, value=%s\n", key, value);
}
which would print:
key=1, value=(1-2,3-4)
key=2, value=2
key=3, value=3
key=4, value=4
You will have to use some look ahead mechanism here. As I see it you are trying to split it on comma that is not in parenthesis. But your regular expressions says:
Split on comma OR on comma between numbers in parenthesis
So your String gets splitted in 4 places 1) (1-2,3-4) 2-4) comma
String[] arr = commaPattern.split(str);
should be
String[] arr = str.split(commaPattern);
commaPattern is not a regex string. Even if you pass string this wouldn't solve the problem with regular expression.