How to use group numbers with Matcher ?

Using group numbers with Macher

The whole pattern is defined to be group number 0.

Any capturing group in the pattern start indexing from 1.

The indices are defined by the order of the opening parentheses of the capturing groups.

EXAMPLE

Regex: ([a-zA-Z0-9]+)([\s]+)([a-zA-Z ]+)([\s]+)([0-9]+)

String: "!* UserName10 John Smith 01123 *!"

group(0): UserName10 John Smith 01123

group(1): UserName10

group(2):

group(3): John Smith

group(4):

group(5): 01123

There are 5 groups which are each enclosed in parentheses.

group(0) gives you the entire matched string.

groups 2 and 4 are simply the white space (space char / line feed / tab)

CODE

Pattern pattern=Pattern.compile("pattern");

Macher matcher=pattern.matcher("string");

if(matcher.matches()) {

  grp0 = matcher.group(0);

  grp1 = matcher.group(1);

  ...

}