java获得本日，本月，本周（周一算开始），本年开始时间0点0分0秒的13位时间戳

获取本日时间戳：

Date date = new Date();
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
long todayStartTime = calendar.getTimeInMillis() / 1000;

获取本月时间戳：

Date date = new Date();
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.set(Calendar.DAY_OF_MONTH, 1);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
long monthStartTime = calendar.getTimeInMillis() / 1000;

获取本周时间戳：

Date date = new Date();
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
long weekStartTime = calendar.getTimeInMillis() / 1000;

获取本年时间戳：

Date date = new Date();
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.set(Calendar.MONTH, 0);
calendar.set(Calendar.DAY_OF_MONTH, 1);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
long yearStartTime = calendar.getTimeInMillis() / 1000;