Java中GregorianCalendar的基本使用

使用默认时区即东八区：

        int  ONE_SECOND = 1000;
         int  ONE_MINUTE = 60*ONE_SECOND;
         int  ONE_HOUR = 60*ONE_MINUTE;
         long ONE_DAY = 24*ONE_HOUR;
         long ONE_WEEK  = 7*ONE_DAY;
         println("one week: " + ONE_WEEK);
        println("one day: " + ONE_DAY);
        GregorianCalendar calendar = new GregorianCalendar(1970,0,1);
        long timestamp = calendar.getTimeInMillis();
        println("timestamp: " + timestamp);
        println("minute: " + timestamp/ONE_MINUTE);        int  ONE_SECOND