Plucking ranged percentages via regex-CodePudding

I am accepting a string from user input and trying to determine if it matches a regex. If it does I need to pluck certain matched groups out of the input and process them.

The valid string must be of the form:

1 number that can consist of integers or floating points (decimal point)
followed by a hyphen ("-")
followed by another number (same as the first)
optionally ended with a percent sign ("%")

Examples of valid string inputs:

"6-9"
"6.5-9"
"6-9.24"
"6-9%"
"6.5-9%"
"6.24-9.23%"

My best attempt:

String numRange = getFromUser();
Pattern pattern = Pattern.compile("([0-9]{1,2}\.[0-9]{1,2})-([0-9]{1,2}\.[0-9]{1,2})[%]*");
Matcher matcher = pattern.matcher(numRange);
if (matcher.matches()) {
    String lowRangeVal = matcher.group(1);
    String highRangeVal = matcher.group(2);

    // continue processing here
}

Does not work. Can anyone spot where I'm going awry?

CodePudding user response：

I modified your pattern to fit your requirement as following.

([0-9]{1,2}(\.[0-9]{1,2})*)-([0-9]{1,2}(\.[0-9]{1,2})*)[%]*

I only added optional (*) to the decimal place and second number part. And I assumed that number before or after the decimal place is limited to length 1 to 2, although you did not say so.

https://regex101.com/r/5fpUB2/1

CodePudding user response：

Use

Pattern pattern = Pattern.compile("(\\d (?:\\.\\d )?)-(\\d (?:\\.\\d )?)%*");

See regex proof.

EXPLANATION

--------------------------------------------------------------------------------
  (                        group and capture to \1:
--------------------------------------------------------------------------------
    \d                       digits (0-9) (1 or more times (matching
                             the most amount possible))
--------------------------------------------------------------------------------
    (?:                      group, but do not capture (optional
                             (matching the most amount possible)):
--------------------------------------------------------------------------------
      \.                       '.'
--------------------------------------------------------------------------------
      \d                       digits (0-9) (1 or more times
                               (matching the most amount possible))
--------------------------------------------------------------------------------
    )?                       end of grouping
--------------------------------------------------------------------------------
  )                        end of \1
--------------------------------------------------------------------------------
  -                        '-'
--------------------------------------------------------------------------------
  (                        group and capture to \2:
--------------------------------------------------------------------------------
    \d                       digits (0-9) (1 or more times (matching
                             the most amount possible))
--------------------------------------------------------------------------------
    (?:                      group, but do not capture (optional
                             (matching the most amount possible)):
--------------------------------------------------------------------------------
      \.                       '.'
--------------------------------------------------------------------------------
      \d                       digits (0-9) (1 or more times
                               (matching the most amount possible))
--------------------------------------------------------------------------------
    )?                       end of grouping
--------------------------------------------------------------------------------
  )                        end of \2
--------------------------------------------------------------------------------
  %*                       '%' (0 or more times (matching the most
                           amount possible))