import java.util.regex.*;
public class Regex2 {
public static void main(String[] args) {
Pattern p = Pattern.compile("\\d*");
Matcher m = p.matcher("ab34ef");
boolean b = false;
while ( m.find()) {
System.out.print(m.start() + m.group());
}
}
}
Why this code produce output: 01234456
@vks is right:
If you are using \\d* it works on each characters:
Index: char = matching:
0: 'a' = "" because no integer
1: 'b' = "" because no integer
2: '3' = "34" because there is two integer between index [2-3]
'4' is not checked because the index has been incremented in previous check.
4: 'e' = ""
5: 'f' = "" because no integer
6: '' = "" IDK
It produce 0, "", 1, "", 2, "34", 4, "", 5, "", 6, "" = 01234456 (that's why you got it).
If you use \\d+ only the groups with one or more integer will match.
\d* means integer 0 or more times.So an empty string between a and b ,before a ...those are also
matched.Use `\d+` to get correct result.
See demo.
