Extracting some information from a String - Java + regex

Question

I'm trying to use regex to extract some information from a String.

I'm working on a program that needs to take a user inputted timeframe, and I need to seperate out the string into each of the units of time(years,months, weeks,days, hours and minutes.)

Example of the String: 1y30d would represent 1 year 30 days. 1y1m30mi would be 1 year 1 month 30 minutes

Any idea how I would go about this? I'm guessing something with regex would do it, but I have never really used regex, so I don't know where to start.

Thanks for any help.

Here is an interactive REGEX tutorial.

takendarkk
– takendarkk

2014-01-25 16:43:19 +00:00
Commented Jan 25, 2014 at 16:43 — takendarkk
– takendarkk, Commented Jan 25, 2014 at 16:43

acdcjunior · Accepted Answer · 2014-01-25 17:11:38Z

If you want to match a pattern like:

1y2m3d45h6mi7s

You could use the following regex (online demo here):

(?:(\d+)y)?(?:(\d+)m(?!i))?(?:(\d+)d)?(?:(\d+)h)?(?:(\d+)mi)?(?:(\d+)s)?

As you can see, it consists in several parts like (?:(\d+)X)?, where X is the character for the time period you want to match. It means:

(?:           open parenthesis, for "non-matching group"
    (\d+)     any number of digits
    X         followed by the character 'X'
)?            and everything is optional

Also, for month, (?:(\d+)m(?!i))?, there is a negative lookahead to make it consider 1mi one minute instead of one month plus the char i (from another information, that is not the date).

And some Java code to work with it (online demo here):

public static void main(String[] args) throws java.lang.Exception {
    parseInformation("1y30d");
    parseInformation("1y2m30mi");
    parseInformation("1y1mi");
    parseInformation("1y2m3d4h5mi6s");
}

public static void parseInformation(String information) {
    Pattern p = Pattern.compile("(?:(\\d+)y)?(?:(\\d+)m(?!i))?(?:(\\d+)d)?(?:(\\d+)h)?(?:(\\d+)mi)?(?:(\\d+)s)?");
    Matcher m = p.matcher(information);
    while (m.find()) {
        if (m.group().isEmpty()) { continue; /* found nothing, go on */ }
        System.out.println(information + " found: '"+m.group()+"'");
        System.out.println("\t" + m.group(1) + " years");
        System.out.println("\t" + m.group(2) + " months");
        System.out.println("\t" + m.group(3) + " days");
        System.out.println("\t" + m.group(4) + " hours");
        System.out.println("\t" + m.group(5) + " minutes");
        System.out.println("\t" + m.group(6) + " seconds");
        System.out.println("");
    }

Output:

...
1y2m3d4h5mi6s found: '1y2m3d4h5mi6s'
    1 years
    2 months
    3 days
    4 hours
    5 minutes
    6 seconds

@M42 You are right, it is safer to consider mi to be minutes instead of month+end of the string. I fixed it, thanks!

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