StringUtil.isEmptyOrSpaces improvements

This is remove usage of 'String.trim()' when checking String for empty(ignoring spaces)

Two 'while' replaced by one 'for'

    public String trim() {
        int len = count;
        int st = 0;
        int off = offset;      /* avoid getfield opcode */
        char[] val = value;    /* avoid getfield opcode */

        while ((st < len) && (val[off + st] <= ' ')) {
            st++;
        }
        while ((st < len) && (val[off + len - 1] <= ' ')) {
            len--;
        }
        return ((st > 0) || (len < count)) ? substring(st, len) : this;
    }