How can I split string using Regular Expression(Pattern)?

Question

I want to split my String (e.g. "20150101") using Regular Expression.
For example I need these values: "2015","01","01"

Use `String.split(String regex)`? There are tons of questions on SO about using regex. What have you tried? — mkobit, Apr 29 '15 at 21:46
Aren't you actually trying to parse this as a date instead? See for example http://stackoverflow.com/questions/28034202/simple-way-to-convert-yyyymmdd-formatted-string-into-a-gregoriancalendar-objec — Didier L, Apr 29 '15 at 22:02
possible duplicate of [How to split a string in Java](http://stackoverflow.com/questions/3481828/how-to-split-a-string-in-java) — Skatox, Apr 29 '15 at 22:06

score 3 · Accepted Answer · edited Apr 29 '15 at 22:20

3

String pattern = "(....)(..)(..)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(inputString);//inputString:"20150101"

Now you can use m.group(x) to get the parts of the string. For example:

m.group(1) is first four digit ("2015" in your question).

edited Apr 29 '15 at 22:20

Nate Barbettini

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answered Apr 29 '15 at 21:47

Mohammadreza Tavakoli

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Are you sure it's not `m.group(0)` for the first group? – Nate Barbettini Apr 29 '15 at 21:58
group 0 is always the entire match – Shahzeb Apr 29 '15 at 21:59

declension · Answer 2 · 2015-04-29T21:54:06.897

3

Bit hard to say without more details, but try:

(\d{4})(\d{2})(\d{2})

Your Matcher's three captured group references will then have the values you want.

edited Apr 29 '15 at 21:54

answered Apr 29 '15 at 21:47

declension

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score 0 · Answer 3 · answered Apr 29 '15 at 22:07

Just combining the two answers both are valid

First

public static void main(String[] args) {
            String input = "20150101";
            String pattern = "(....)(..)(..)";
            Pattern r = Pattern.compile(pattern);
            Matcher m = r.matcher(input);       
            m.find();
            for(int i=1;i<=m.groupCount();i++){
                String token = m.group( i ); 
                  System.out.println(token);
            }
    }

Second

public static void main(String[] args) {
            String input = "20150101";
            String pattern = "(\\d{4})(\\d{2})(\\d{2})";
            Pattern r = Pattern.compile(pattern);
            Matcher m = r.matcher(input);       
            m.find();
            for(int i=1;i<=m.groupCount();i++){
                String token = m.group( i ); 
                  System.out.println(token);
            }
    }

score 0 · Answer 4 · answered Apr 29 '15 at 22:21

private static final Pattern DATE_PATTERN = Pattern.compile("^([\\d]{4})([\\d]{2})([\\d]{2})$");

public static Optional<String[]> split(String str) {
    final Matcher matcher = DATE_PATTERN.matcher(str);
    if (matcher.find()) {
        final String[] array = new String[3];
        array[0] = matcher.group(1);
        array[1] = matcher.group(2);
        array[2] = matcher.group(3);
        return Optional.of(array);
    }
    return Optional.empty();
}

How can I split string using Regular Expression(Pattern)?

4 Answers4