java如何从不规则的字符串中截取出日期

 				 // 截取时间处理 -- java8
				//content是获取的字符串
                    List<String> lists = Collections.singletonList(content);
                    String beginDate = lists.stream().map(e -> {
                        int lastIndexOf = e.lastIndexOf(":00");
                        int indexOf = e.indexOf("）");
                        String substring = e.substring(indexOf + 1, lastIndexOf + 3);
                        String trim = substring.replace(",", "").trim();
                        return trim;
                    }).findFirst().orElse(null);

 					 
                    List<String> lists = Collections.singletonList(content);
                    String beginDate = lists.stream().map(e -> {
                        int lastIndexOf;
                        int indexOf;
                        String trim;
                        lastIndexOf = e.lastIndexOf("到");
                        if (lastIndexOf == -1) {
                            lastIndexOf = e.lastIndexOf(":00");
                            if (lastIndexOf == -1) {// 防止不规则的字符串时间报错,至为空
                                return "";
                            }
                            indexOf = e.indexOf("，");
                            trim = e.substring(indexOf + 1, lastIndexOf + 3);
                        } else {
                            indexOf = e.indexOf("，");
                            String substring = e.substring(indexOf + 1, lastIndexOf);
                            trim = substring.replace(",", "").trim();
                        }
                        return trim;
                    }).findFirst().orElse(null);
                    String b = beginDate.replaceAll("[年,月]", "-");
                    // 至为空相关处理 -- 三目运算符 resultDto是自定义的实体
                    resultDto.setBeginDate(b.equals("") ? null : b);

public static String toDate(String str) {
    String pattern = "\\d{4}\\/\\d{1,2}\\/\\d{1,2}";
    if (str != null && Pattern.matches(pattern, str)) {
        String[] date = StringUtils.split(str, "\\/");
        Calendar c1 = Calendar.getInstance();
        c1.set(Integer.parseInt(date[0]), Integer.parseInt(date[1]) - 1, Integer.parseInt(date[2]));
        
        SimpleDateFORMat sdf = new SimpleDateFormat("yyyy/MM/dd");
        return sdf.format(c1.getTime());
    }
    return null;
}