@神笔码农:

LocalDate nowDate = LocalDate.now();

System.out.println("本年第一天:" + nowDate.with(TemporalAdjusters.firstDayOfYear()));

System.out.println("本年最后一天:" + nowDate.with(TemporalAdjusters.lastDayOfYear()));

System.out.println("本月第一天:" + nowDate.with(TemporalAdjusters.firstDayOfMonth()));

System.out.println("本月最后一天:" + nowDate.with(TemporalAdjusters.lastDayOfMonth()));

System.out.println("本周第一天:" + nowDate.with(DayOfWeek.MONDAY));

System.out.println("本周最后一天:" + nowDate.with(DayOfWeek.SUNDAY));