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

Answer 1

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()

Answer 2

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

Answer 3

How about This reverts (?:commit )?([af\\\\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

Answer 4

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 .

Answer 5

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...