I'm trying to get the digits from the expression [1..1], using Java's split method. I'm using the regex expression ^\\[|\\.{2}|\\]$ inside split. But the split method returning me String array with first value as empty, and then "1" inside index 1 and 2 respectively. Could anyone please tell me what's wrong I'm doing in this regex expression, so that I only get the digits in the returned String array from split method?
4 Answers
You should use matching. Change your expression to:
`^\[(.*?)\.\.(.*)\]$`
And get your results from the two captured groups.
As for why split acts this way, it's simple: you asked it to split on the [ character, but there's still an "empty string" between the start of the string and the first [ character.
answered Jan 10, 2016 at 15:42
Lucas Trzesniewski
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Your regex is matching [ and .. and ]. Thus it will split at this occurrences.
You should not use a split but match each number in your string using regex.
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You've set it up such that [, ] and .. are delimiters. Split will return an empty first index because the first character in your string [1..1] is a delimiter. I would strip delimiters from the front and end of your string, as suggested here.
So, something like
input.replaceFirst("^[", "").split("^\\[|\\.{2}|\\]$");
Or, use regex and regex groups (such as the other answers in this question) more directly rather than through split.
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Why not use a regex to capture the numbers? This will be more effective less error prone. In that case the regex looks like:
^\[(\d+)\.{2}(\d+)\]$
And you can capture them with:
Pattern pat = Pattern.compile("^\\[(\\d+)\\.{2}(\\d+)\\]$");
Matcher matcher = pattern.matcher(text);
if(matcher.find()) { //we've found a match
int range_from = Integer.parseInt(matcher.group(1));
int range_to = Integer.parseInt(matcher.group(2));
}
with range_from and range_to the integers you can no work with.
The advantage is that the pattern will fail on strings that make not much sense like ..3[4, etc.
answered Jan 10, 2016 at 15:42
willeM_ Van Onsem
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\\d?\\d+since the numbers can probably be larger than9.