Question

What regex/pattern can I use to find the following pattern in a string?

#nnnn:

nnnn can be any 4-digit long number as long as it is sorrounded by a hashtag and a colon.

I have tried the code below:

String string = "#8226:";
if(string.matches( ".*\\d:.*" )) {
  System.out.println( "Yes" );
}

It DOES work, but it matches other strings like below:

"This is a string 1234: Hahaha!" // Outputs "Yes"
"Hello 1834: World!!!"           // Outputs "Yes"

I want it to only match the pattern at the top of the question.

Can anybody tell me where did I go wrong?

Answer 1

It can be done with Regular Expression

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class FindPattern {
    public static void main(String[] args) {
        Pattern pattern = Pattern.compile("#[0-9]{4}:");

        String text = "#1233:#3433:abc#3993: #a343:___#8888:ki";
        Matcher matcher = pattern.matcher(text);
        while (matcher.find()) {
            System.out.println(matcher.group());
        }

    }
}

output is:

#1233:
#3433:
#3993:
#8888: