java 获取前几天日期、上个月某天的日期

public void getDate(){

//获取前几天日期

    Calendar calendar = Calendar.getInstance();

    SimpleDateFormat simpleDateFormat =new SimpleDateFormat("yyyy-MM-dd");

    calendar.setTime(new Date());

    //三天前

    calendar.set(Calendar.DATE,calendar.get(Calendar.DATE)-3);

    //三天前零点

    String thirdDate = simpleDateFormat.format(calendar.getTime()) +" " +"00:00:00";

    //获取上一个月第一天日期

    Calendar calendar1 = Calendar.getInstance();

    //上个月

    calendar1.add(Calendar.MONTH,-1);

    //该月第一天

    calendar1.set(Calendar.DAY_OF_MONTH,1);

    //上个月第一天日期23点59分59秒

    String lastMonthFirstDay = simpleDateFormat.format(calendar1.getTime()) +" " +"23:59:59";

    //获取上个月最后一天日期

    Calendar calendar2=Calendar.getInstance();

    int month=calendar2.get(Calendar.MONTH);

    calendar2.set(Calendar.MONTH, month-1);

    calendar2.set(Calendar.DAY_OF_MONTH, calendar2.getActualMaximum(Calendar.DAY_OF_MONTH));

    String lastMonthEndDay = simpleDateFormat.format(calendar2.getTime()) +" " +"23:59:59";

    System.out.println("三天前零点："+thirdDate);

    System.out.println("上一个月第一天日期："+lastMonthFirstDay);

    System.out.println("上个月最后一天日期："+lastMonthEndDay);

}