下一个范围在当前范围的最后一天之后开始。您可以迭代日期范围字符串列表，并查找不符合此规则的连续范围。此时，使用此规则创建缺少的范围并中断循环。
演示：

import java.time.LocalDate;
import java.util.List;

class Main {
    public static void main(String[] args) {
        List<String> dateRangeList = List.of("2019-01-01 2019-02-01", "2019-02-02 2019-04-04", "2019-06-01 2019-07-01");
        for (int i = 0; i < dateRangeList.size() - 1; i++) {
            String[] currentRange = dateRangeList.get(i).split(" ");
            String[] nextRange = dateRangeList.get(i + 1).split(" ");
            LocalDate oneDayAfterLastDateOfCurrentRange = LocalDate.parse(currentRange[1]).plusDays(1);
            LocalDate firstDateOfNextRange = LocalDate.parse(nextRange[0]);
            if (!oneDayAfterLastDateOfCurrentRange.equals(firstDateOfNextRange)) {
                String missingDateRange = oneDayAfterLastDateOfCurrentRange.toString() + " "
                        + firstDateOfNextRange.minusDays(1);
                System.out.println("The missing date range is: " + missingDateRange);
                break;
            }
        }
    }
}

输出：

The missing date range is: 2019-04-05 2019-05-31