java String regex pattern match and replace string

Question

There is a string, if that pattern matches need to return first few char's only.

String str = "PM 17/PM 19 - Test String";

expecting return string --> PM 17

Here my String pattern checking for:

1) always starts with PM
2) then followed by space (or some time zero space)
3) then followed by some number
4) then followed by slash (i.e. /)
5) then followed by Same string PM
6) then followed by space (or some time zero space)
7) Then followed by number
8) then any other chars/strings.

If given string matches above pattern, I need to get string till before the slash (i.e. PM 17)

I tried below way but it did not works for the condition.

  if(str.matches("PM\\s+[0-9.]/PM(.*)")) { //"PM//s+[0-9]/PM(.*)"
                  str = str.substring(0, str.indexOf("/"));
                  flag = true;
  }

next issue: [0-9] matches one digit, not multiple such as 17. — f1sh
– f1sh, Commented Oct 8, 2019 at 15:19
//s+ means "two forward slashes, literal s character repeated 1 to infinity times". You probably meant \\s+ — VLAZ
– VLAZ, Commented Oct 8, 2019 at 15:19

anubhava · Accepted Answer · 2019-10-08 15:37:44Z

1

Instead of .matches you may use .replaceFirst here with a capturing group:

str = str.replaceFirst( "^(PM\\s*\\d+)/PM\\s*\\d+.*$", "$1" );
//=> PM 17

RegEx Demo

RegEx Details:

^: Line start
(PM\\s*\\d+): Match and group text starting with PM followed by 0 or more whitespace followed by 1 or more digits
/PM\\s*\\d+: Match /PM followed by 0 or more whitespace followed by 1 or more digits
.*$: Match any # of characters before line end
$1: is replacement that puts captured string of first group back in the replacement.

If you want to do input validation before substring extraction then I suggest this code:

final String regex = "(PM\\s*\\d+)/PM\\s*\\d+.*";    
final Pattern pattern = Pattern.compile(regex);
final Matcher matcher = pattern.matcher(str);

if (matcher.matches()) {
    flag = true;
    str = matcher.group(1);
}

edited Oct 8, 2019 at 15:37

answered Oct 8, 2019 at 15:23

anubhava

790k67 gold badges603 silver badges671 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

java String regex pattern match and replace string

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related