public String getNumber() {
        String re = "";
        int x = this.getBegin();
        while (this.getBegin() < this.getCad().length() && (this.getCad().charAt(x) + "").matches(this.getMatchNum())) {
            re = re + this.getCad().charAt(x++);
            this.setBegin(x);
        }
        return re.equals("") ? null : re;
    }