Retrieve a String using regular expression on java

Question

I have these lines:

This reverts commit c289f6fa1f8642a5caf728ef8ff87afd5718cd99.
This reverts commit c7740a943ec896247ebc5514b6be02710caf3c53.  There should
This reverts 518920b764ee9150781e68217181b24d0712748e commit.

How can i do with regular expression on java to retrieve only numbers:

c289f6fa1f8642a5caf728ef8ff87afd5718cd99
c7740a943ec896247ebc5514b6be02710caf3c53
518920b764ee9150781e68217181b24d0712748e

So you want to get rid of all the words and .? You can use String#split("\\s+") — Smit
– Smit, Commented Jun 13, 2013 at 16:17
If you want to manipulate git repositories in Java, there is a library for that — fge
– fge, Commented Jun 13, 2013 at 16:19
Are you sure you will only have these hashes in this kind of context? If you intend to manage all the GIT messages searching for "reverts" won't be enough... — Pragmateek
– Pragmateek, Commented Jun 13, 2013 at 16:35

fge · Accepted Answer · 2013-06-13 16:31:00Z

3

Recommendation: use JGit.

If you really insist on doing this using a regular expression, then you can use this regex:

\b[a-f0-9]{40}\b

using:

final Pattern sha1Pattern = Pattern.compile("\\b[a-f0-9]{40}\\b");

final Matcher matcher = sha1Pattern.matcher(yourInput);
if (matcher.find())
    // sha1 is accessed via matcher.group()

edited Jun 13, 2013 at 16:31

answered Jun 13, 2013 at 16:22

fge

122k35 gold badges266 silver badges340 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Pshemo Over a year ago

I don't know any 40 letter word containing only a-f letters which could give false positive result so +1 :) BTW you probably want to change 20 to 40

fge Over a year ago

@Pshemo oops... I always seem to forget that it takes two hexadecimal digits per byte :p

Mehdi Over a year ago

It does not work ! may be you make mistakes on your regular expression ?

fge Over a year ago

@Mehdi no reason why it shouldn't work, but again, if I were to manipulate git repositories in Java I'd go the JGit way ;)

fge Over a year ago

@Mehdi yes, the 20 was the cause... \\b is the word anchor, and [a-f0-9] is a character class. {n} is a quantifier meaning "exactly n times"

|

Mena · Accepted Answer · 2013-06-13 16:22:29Z

If you need the full alphanumeric hashes rather than only digits, consider using this example:

String test1 = "This reverts commit c289f6fa1f8642a5caf728ef8ff87afd5718cd99.";
String test2 = "This reverts commit c7740a943ec896247ebc5514b6be02710caf3c53.  There should";
String test3 = "This reverts 518920b764ee9150781e68217181b24d0712748e commit.";
Pattern pattern = Pattern.compile("reverts\\s(commit\\s)*(.+?)[\\.\\s]");
Matcher matcher = pattern.matcher(test1);
if (matcher.find()) {
    System.out.println(matcher.group(2));
}
matcher = pattern.matcher(test2);
if (matcher.find()) {
    System.out.println(matcher.group(2));
}
matcher = pattern.matcher(test3);
if (matcher.find()) {
    System.out.println(matcher.group(2));
}

Output:

c289f6fa1f8642a5caf728ef8ff87afd5718cd99
c7740a943ec896247ebc5514b6be02710caf3c53
518920b764ee9150781e68217181b24d0712748e

Sergey Kalinichenko · Accepted Answer · 2013-06-13 16:25:52Z

1

It looks like a little hack of retrieving the sequence of 40 alphanumeric characters should do the trick. Use this pattern \p{Alnum}{40}; the only match in your test string is going to be the commit number.

static final String[] data = new String[] {
    "This reverts commit c289f6fa1f8642a5caf728ef8ff87afd5718cd99.",
    "This reverts commit c7740a943ec896247ebc5514b6be02710caf3c53.  There should",
    "This reverts 518920b764ee9150781e68217181b24d0712748e commit."
};
public static void main (String[] args) throws java.lang.Exception {
    Pattern p = Pattern.compile("\\p{Alnum}{40}");
    for (String s : data) {
        Matcher m = p.matcher(s);
        if (m.find()) {
             System.out.println(m.group());   
        }
    }
}

This prints

c289f6fa1f8642a5caf728ef8ff87afd5718cd99
c7740a943ec896247ebc5514b6be02710caf3c53
518920b764ee9150781e68217181b24d0712748e

Demo on ideone.

answered Jun 13, 2013 at 16:25

Sergey Kalinichenko

729k85 gold badges1.2k silver badges1.6k bronze badges

1 Comment

Pragmateek Over a year ago

I think the hash is made of only hexadecimal numbers, so you can be more restrictive: [a-f0-9]

Pshemo · Accepted Answer · 2013-06-13 16:31:08Z

1

How about This reverts (?:commit )?([a-f\\d]+)? This should store searched part in group 1

String data="This reverts commit c289f6fa1f8642a5caf728ef8ff87afd5718cd99." +
        "This reverts commit c7740a943ec896247ebc5514b6be02710caf3c53.  There should" +
        "This reverts 518920b764ee9150781e68217181b24d0712748e commit.";

Matcher m = Pattern.compile("This reverts (?:commit )?([a-f\\d]+)").matcher(data);
while(m.find())
    System.out.println(m.group(1));

output:

c289f6fa1f8642a5caf728ef8ff87afd5718cd99
c7740a943ec896247ebc5514b6be02710caf3c53
518920b764ee9150781e68217181b24d0712748e

edited Jun 13, 2013 at 16:31

answered Jun 13, 2013 at 16:23

Pshemo

125k25 gold badges194 silver badges280 bronze badges

4 Comments

Pragmateek Over a year ago

IMHO not generic enough, this kind of hash could appear with other messages than what the OP presented to illustrate the idea, but good foe this subset.

Pshemo Over a year ago

@Pragmateek True, but without knowing the real purpose of this question is hard to give good more general answer. fge's answer is probably the closes but am not sure if OP input wont have strings like caaaaaaafeeeeeeeeeeeee(repeat e until 40 letter word) :)

Pragmateek Over a year ago

right. And such a long word would be really bad, even in french we don't have that ;) But if it's for managing some chemical industry related code: worldwidewords.org/qa/qa-imm1.htm should be possible if no "i"

Pshemo Over a year ago

@Pragmateek good one :D. I am also wondering if OP input wont have any chemical formulas containing only a-f characters like Ac B Ba Be C Ca Cd Ce Cf Db F Fe and digits :)

Pragmateek · Accepted Answer · 2013-06-13 16:29:12Z

I don't think you can do a better job than matching sequences of 40 character representing hexadecimal numbers.

Here is a full example (could be refined but it's the idea):

public static void main(String[] args) throws Exception
{   
    String s = "This reverts commit c289f6fa1f8642a5caf728ef8ff87afd5718cd99.\n" + 
               "This reverts commit c7740a943ec896247ebc5514b6be02710caf3c53.  There should\n"+
               "This reverts 518920b764ee9150781e68217181b24d0712748e commit.\n";

    Pattern pattern = Pattern.compile("[a-f0-9]{40}");
    Matcher matcher = pattern.matcher(s);

    while (matcher.find())
    {
        String m = matcher.group();

        System.out.println(m);
    }
}

But I may be wrong...

Collectives™ on Stack Overflow

Retrieve a String using regular expression on java

5 Answers 5

6 Comments

Comments

1 Comment

4 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

6 Comments

Comments

1 Comment

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related