Java如何利用LocalDate获取某个月的第一天与最后一天日期

LocalDate date = LocalDate.now();
LocalDate firstDay = date.with(TemporalAdjusters.firstDayOfMonth()); // 获取当前月的第一天
LocalDate lastDay = date.with(TemporalAdjusters.lastDayOfMonth()); // 获取当前月的最后一天
System.out.println(date);
System.out.println(firstDay);
System.out.println(lastDay);

LocalDate date = LocalDate.now();
LocalDate lastMonth = date.minusMonths(1); // 当前月份减1
LocalDate firstDay = lastMonth.with(TemporalAdjusters.firstDayOfMonth()); // 获取当前月的第一天
LocalDate lastDay = lastMonth.with(TemporalAdjusters.lastDayOfMonth()); // 获取当前月的最后一天
System.out.println(day);
System.out.println(lastMonth);
System.out.println(firstDay);
System.out.println(lastDay);

LocalDate date = LocalDate.of(2021, 3, 14);
LocalDate lastMonth = date.minusMonths(1); // 当前月份减1
LocalDate firstDay = lastMonth.with(TemporalAdjusters.firstDayOfMonth()); // 获取当前月的第一天
LocalDate lastDay = lastMonth.with(TemporalAdjusters.lastDayOfMonth()); // 获取当前月的最后一天
System.out.println(day);
System.out.println(lastMonth);
System.out.println(firstDay);
System.out.println(lastDay);

LocalDate date = LocalDate.of(2021, 8, 8);
LocalDate lastMonthEnd = date.minusDays(-date.getDayOfMonth()); // 日期date减去这个月已有的天数，得到上个月的最后一天
LocalDate lastMonthBegin = LocalDate.of(lastMonthEnd.getYear(), lastMonthEnd.getMonthValue(), 1); // 通过上一步得到的上个月的最后一天，得到上个月的第一天
System.out.println(date);
System.out.println(lastMonthBegin);
System.out.println(lastMonthEnd);

LocalDateTime date = LocalDateTime.now();
LocalDateTime firstday = date.with(TemporalAdjusters.firstDayOfMonth());
LocalDateTime lastDay = date.with(TemporalAdjusters.lastDayOfMonth());

/**
  * 获取指定日期当月的第一天
  * @param dateStr
  * @param format
  * @return
  */
 public static String getFirstDayOfGivenMonth(String dateStr,String format){undefined
 SimpleDateFormat sdf = new SimpleDateFormat(format); 
 try {undefined
 Date date = sdf.parse(dateStr);
 Calendar calendar = Calendar.getInstance();
 calendar.setTime(date);
 calendar.set(Calendar.DAY_OF_MONTH,1);
 calendar.add(Calendar.MONTH, 0);
 return sdf.format(calendar.getTime());
 } catch (ParseException e) {undefined
 e.printStackTrace();
 }
 return null;
 }

/**

  * 获取指定日期下个月的第一天
  * @param dateStr
  * @param format
  * @return
  */
 public static String getFirstDayOfNextMonth(String dateStr,String format){
 SimpleDateFormat sdf = new SimpleDateFormat(format); 
 try {
 Date date = sdf.parse(dateStr);
 Calendar calendar = Calendar.getInstance();
 calendar.setTime(date);
 calendar.set(Calendar.DAY_OF_MONTH,1);
 calendar.add(Calendar.MONTH, 1);
 return sdf.format(calendar.getTime());
 } catch (ParseException e) {
 e.printStackTrace();
 }
 return null;
 }