/**
 * 判斷日期範圍是否有重疊(日期到天)
 * @param list
 * @return
 */
public static boolean overlapping(List<String> list) {
    if (list == null || list.size() <= 1) {
        return false;
    }
    for (int i = 0; i < list.size(); i++) {
        String dateRange [] = list.get(i).split(" ");
        Date startDate = stringToDate(dateRange[0],"yyyy-MM-dd");
        Date endDate = stringToDate(dateRange[1], "yyyy-MM-dd");
        for (int j = i + 1; j < list.size(); j++) {
            String dateRangeJ [] = list.get(j).split(" ");
            Date startDateJ = stringToDate(dateRangeJ[0],"yyyy-MM-dd");
            Date endDateJ = stringToDate(dateRangeJ[1], "yyyy-MM-dd");

            if (!startDateJ.before(startDate)) {
                if (!startDateJ.after(endDate)) {
                    return true;
                }
            } else if (!endDateJ.before(startDate)) {
                return true;
            }
        }
    }
    return false;
}

返回true表示有重疊  false表示無重疊

呼叫示例：

List<String> dateRanges = new ArrayList<>();
dateRanges.add("2021-10-01 2021-10-03");
dateRanges.add("2021-10-04 2021-10-05");
dateRanges.add("2021-10-05 2021-10-06");

overlapping（dateRanges）；