get matches words by regex java

I need a method for getting whole word if matches a pattern, for exemple:

<p>This is some text. <img src="md5_id=12345" </p>

I'll need to get md5_id=12345, so pattern will be smth like :...md5_id:xxxxx... where x can be 0-9 or a-z/A-Z

I got the solution...

    private void method(String txt) {
    Pattern pattern = Pattern.compile(("md5_id=[a-zA-Z_0-9]{5,}"));

    Matcher m = pattern.matcher(txt);
    while (m.find()) {
        Log.d("log", m.group());

    }
}