java regular Expression, fetching time out of a string

Question

I am new to regex in java..

i have a string "2:05pm - 2:40 pm" i need to get "2:05pm" and "2:40 pm" out from the single string using regex

I am using the follow regex expression, but I am getting wrong somewhere, don't know where

public static void main(String args[])
{
    Pattern MY_PATTERN = Pattern.compile("(\\d+)[:](\\d+)(\\s*)((am?)|(pm?))");
    String s = "2:05pm - 2:40pm";
    Matcher m = MY_PATTERN.matcher(s);
    int i=1;
    while (m.find()) {
        System.out.println(m.group(i++));
    }
}

Marko Topolnik · Accepted Answer · 2013-11-17 11:04:13Z

1

Your usage of group is wrong: you must always use group(0), which refers to the entire current match.

Overall, your regex is much too complicated, this is enough:

"\\d+:\\d+\\s*(a|p)m?"

which works in case you want input such as 1:10 a and 1:10p accepted, but not 1:10. Otherwise you should use this:

"\\d+:\\d+\\s*(am|pm)?"

which will accept 1:10, 1:10 am, but not 1:10 a.

If you want to validate a maximum of two digits, then use \\d{1,2} where you now use \\d+.

edited Nov 17, 2013 at 11:04

answered Nov 17, 2013 at 10:50

Marko Topolnik

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4 Comments

Steve P. Over a year ago

This is only true if you assume valid input (and that the posted in the only acceptable format, which seems like a decent assumption). This accepts 23325:24.

Marko Topolnik Over a year ago

I am carrying over OP's own assumptions since I don't want to entertain too much guesswork.

ItachiUchiha Over a year ago

What if i want to just accept max of two digits before and after :

Marko Topolnik Over a year ago

@ItachiUchiha I added that to the answer.

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