code: public static String find(CharSequence self, CharSequence regex) {
          return find(self, Pattern.compile(regex.toString()));
      }
docs: Finds the first occurrence of a regular expression String within a String.
  If the regex doesn't match, null will be returned.
  <p>
  For example, if the regex doesn't match the result is null:
  <pre>
  assert null == "New York, NY".find(/\d{5}/)
  </pre>
  
  If it does match, we get the matching string back:
  <pre>
  assert "10292" == "New York, NY 10292-0098".find(/\d{5}/)
  </pre>
  
  If we have capture groups in our expression, we still get back the full match
  <pre>
  assert "10292-0098" == "New York, NY 10292-0098".find(/(\d{5})-?(\d{4})/)
  </pre>
  
  @param self  a CharSequence
  @param regex the capturing regex
  @return a String containing the matched portion, or null if the regex doesn't match
  @see #find(String, java.util.regex.Pattern)
  @since 1.8.2