日期获取Calendar，获取本周第一天，本月第一天，往前7天，往前30的日期

分手后的思念是犯贱 2023-06-25 02:24 10阅读 0赞

### 获取每个月的第一天 ###

public static String getFirstDay(Date date){ 
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(date);
            calendar.set(Calendar.DAY_OF_MONTH, 1);
            Date firstDayOfMonth = calendar.getTime();
            return simpleDateFormat.format(firstDayOfMonth);
        }

### 获取每个月的最后一天 ###

public static String getLastDate(Date date){ 
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(date);
            calendar.set(Calendar.DAY_OF_MONTH, 1);
            calendar.add(Calendar.MONTH, 1);//加一个月
            calendar.add(Calendar.DAY_OF_MONTH, -1);
            Date lastDayOfMonth = calendar.getTime();
            return simpleDateFormat.format(lastDayOfMonth);
        }

### 获取每周的第一天 ###

public static String getFirstOfWeek(Date date){ 
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(date);
            calendar.set(Calendar.DAY_OF_WEEK, 2);
            Date firstDayOfMonth = calendar.getTime();
            return simpleDateFormat.format(firstDayOfMonth);
        }

### 获取每周的最后一天 ###

public static String getLastOfWeek(Date date){ 
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(date);
            calendar.set(Calendar.DAY_OF_WEEK, 2);
            calendar.add(Calendar.WEEK_OF_MONTH,1);//加一周
            calendar.add(Calendar.DAY_OF_WEEK,-1);//在当前时间上减去天数
            Date firstDayOfMonth = calendar.getTime();
            return simpleDateFormat.format(firstDayOfMonth);
        }

### 获取当前时间减去7天 ###

public static String before7Days(Date date){ 
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(date);
            calendar.add(Calendar.DAY_OF_MONTH, -7);//在当前时间上减去天数
            Date before7Days = calendar.getTime();
            return simpleDateFormat.format(before7Days);
        }

### 获取当前时间减去30天 ###

public static String before30Days(Date date){ 
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(date);
            calendar.add(Calendar.DAY_OF_MONTH, -30);//在当前时间上减去天数
            Date before7Days = calendar.getTime();
            return simpleDateFormat.format(before7Days);
        }