LocalDate 解析年月字符串

public static void main(String[] args) {
    // ① 调整 DateTimeFormatter
     DateTimeFormatter fmt = new DateTimeFormatterBuilder()
            .appendPattern("yyyy-MM")
        // 添加默认日期
            .parseDefaulting(ChronoField.DAY_OF_MONTH, 1)
            .toFormatter();
    // ② 使用 YearMonth 转换
    YearMonth yearMonth = YearMonth.parse("2021-01", fmt);
    LocalDate localDate = yearMonth.atEndOfMonth();
}