Java Regular Expression Matching for hh:mm:ss in String

Question

I am parsing a file and it has time based entries in it. format is like:

00:02:10-XYZ:Count=10
00:04:50-LMK:Count=3

Here what I want is to extract the time value from string line

I have searched many links and couldn't find out the thing what I want, eventually I have written this code.

    Pattern pattern = Pattern.compile("((?i)[0-9]{1,2}:??[0-9]{0,2}:??[0-9]{0,2})"); //(?i)[0-9]{1,2}:??[0-9]{0,2}:??[0-9]{0,2}  //\\d{1,2}:\\d{1,2}:\\d{1,2}
    Matcher matcher;
    List<String> listMatches;

Below is the loop where I apply logic

    for(int x = 0; x < file_content.size(); x++)
    {
            matcher= pattern.matcher(file_content.get(x));
            listMatches = new ArrayList<String>();
            while(matcher.find())
            {
                listMatches.add(matcher.group(1));
                break;
            }
     }

I want when "matcher.find()" gives true it returns me [00:02:10] in first iteration and [00:04:50] in 2nd iterations.

have you considered using SimpleDateFormat instead of writing your own regex? — Ivaylo Strandjev
– Ivaylo Strandjev, Commented Sep 26, 2013 at 13:39

Gibolt · Accepted Answer · 2019-01-26 01:07:18Z

6

Seems like an unnecessarily complicated pattern.... why not just (if you are doing line-by-line processing):

"^(\\d\\d:\\d\\d:\\d\\d)"

If you are doing multi-line processing you will want to use:

"(?m)^(\\d\\d:\\d\\d:\\d\\d)"

Here's some example code and output:

public static void main(String[] args) {
    final Pattern pattern = Pattern.compile("(?m)^(\\d\\d:\\d\\d:\\d\\d)");
    final Matcher matcher = pattern.matcher("00:02:10-XYZ:Count=10\n00:04:50-LMK:Count=3");
    while(matcher.find())
    {
        System.out.printf("[%s]\n", matcher.group(1));
    }        
}

outputs

[00:02:10]
[00:04:50]

edited Jan 26, 2019 at 1:07

Gibolt

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answered Sep 26, 2013 at 13:41

rolfl

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1 Comment

Bohemian Over a year ago

What about input like 99:99:99? Your regex matches non-time values :( p.s. and why group the match? Did you know you can just get group zero?

DareDevil · Accepted Answer · 2013-09-26 13:54:42Z

I did with this way.

00:02:10-XYZ:Count=10
00:04:50-LMK:Count=3

Pattern pattern = Pattern.compile("([2][0-3]|[0-1][0-9]|[1-9]):[0-5][0-9]:([0-5][0-9]|[6][0])");
//File Beginning Time
for(int x = 0; x < file_content.size(); x++)
   {
        matcher= pattern.matcher(file_content.get(x));
        ListMatches = new ArrayList<String>();
        if(matcher.find())
          {
                start_time = matcher.group();
                break;
          }                
    }
//File End Time
for(int x = file_content.size()-1; x > 0 ; x--)
        {
            matcher= pattern.matcher(file_content.get(x));
            listMatches = new ArrayList<String>();
            if(matcher.find())
            {
                end_time = matcher.group();
                break;
            }                  
        }

Boris the Spider · Accepted Answer · 2013-09-26 13:50:38Z

3

Don't use regex for this, use a SimpleDateFormat. This has two massive advantages

The code in SimpleDateFormat is tested and robust
The SimpleDateFormat will validate to ensure that you have real time numbers

This would look something like this:

public static void main(String[] args) throws Exception {
    final String s = "00:02:10-XYZ:Count=10\n"
            + "00:04:50-LMK:Count=3";
    final Scanner sc = new Scanner(s);
    final SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
    while(sc.hasNextLine()) {
        final String line = sc.nextLine();
        final Date date = dateFormat.parse(line);
        final Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        System.out.println(calendar.get(Calendar.HOUR));
        System.out.println(calendar.get(Calendar.MINUTE));
        System.out.println(calendar.get(Calendar.SECOND));
    }
}

Output:

From the javadoc for DateFormat.parse:

Parses text from the beginning of the given string to produce a date. The method may not use the entire text of the given string.

So the SimpleDateFormat will parse the String until it reads the whole pattern specified then stops.

edited Sep 26, 2013 at 13:50

answered Sep 26, 2013 at 13:44

Boris the Spider

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2 Comments

Anirudha Over a year ago

seems like it should be ("KK:mm:ss")

Boris the Spider Over a year ago

@Anirudh, you're right - it shouldn't be hh, but I think it should be HH.

Anirudha · Accepted Answer · 2013-09-26 13:57:23Z

3

SimpleDateFormat dateFormat = new SimpleDateFormat("KK:mm:ss");    
Pattern pattern = Pattern.compile("\\d+:\\d+:\\d+");
Matcher matcher;
List<Date> listMatches = new ArrayList<Date>();
for(int x = 0; x < file_content.size(); x++)
{
    matcher= pattern.matcher(file_content.get(x));
    while(matcher.find())
    {
        Date temp=null;
        try{temp=dateFormat.parse(matcher.group(0));}catch(ParseException p){}
        if(temp!=null)
        listMatches.add(temp);
    }
}

edited Sep 26, 2013 at 13:57

answered Sep 26, 2013 at 13:52

Anirudha

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