code: public boolean find(int start) {
          int limit = matcher.targetEnd();
          if ((start < 0) || (start > limit))
              throw new IndexOutOfBoundsException("Illegal start index");
          reset();
          matcher.setPosition(start);
          return matcher.find();
      }
docs: Resets this matcher and then attempts to find the next subsequence of
  the input sequence that matches the pattern, starting at the specified
  index.
  
  <p> If the match succeeds then more information can be obtained via the
  <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods, and subsequent
  invocations of the {@link #find()} method will start at the first
  character not matched by this match.  </p>
  
  @throws  IndexOutOfBoundsException
  If start is less than zero or if start is greater than the
  length of the input sequence.
  
  @return  <tt>true</tt> if, and only if, a subsequence of the input
  sequence starting at the given index matches this matcher's
  pattern