Calendar类经常使用的场景

电玩女神 2022-02-28 04:40 212阅读 0赞

参考博客：[https://blog.csdn.net/tiantangdizhibuxiang/article/details/77429346][https_blog.csdn.net_tiantangdizhibuxiang_article_details_77429346]

## 使用场景 ##

#### 1、计算两个任意时间中间相隔的天数 ####

这个使用场景较多，如查询某个时间段注册的新用户，或者某个时间段内销售总额等等。

public int getDaysBetween (Calendar day1, Calendar day2){   
                if (day1.after(day2)){   
                    Calendar swap = day1;  
                    day1 = day2;  
                    day2 = swap;  
                }  
                int days = day2.get(Calendar.DAY_OF_YEAR) - day1.get(Calendar.DAY_OF_YEAR);  
                int y2 = day2.get(Calendar.YEAR);  
                if (day1.get(Calendar.YEAR) != y2){   
                    day1 = (Calendar) day1.clone();  
                    do{   
                        days += day1.getActualMaximum(Calendar.DAY_OF_YEAR);//得到当年的实际天数 
                        day1.add(Calendar.YEAR, 1);  
                    } while (day1.get(Calendar.YEAR) != y2);  
                }  
                return days;  
            }  
         @Test  
         public void getDaysBetweenTest(){   
             Calendar calendar1=Calendar.getInstance();   
             Calendar calendar2=Calendar.getInstance();   
             calendar1.set(2017,07,30);  
             calendar2.set(2017,07,03);  
             int days=getDaysBetween(calendar1, calendar2);  
             System.out.println("相隔"+days+"天");  
         }

#### 2、获取今天或者之后多少天的日期 ####

Calendar calendar=Calendar.getInstance();     
          
        @Test  
        public void getTest(){   
            calendar.setTime(new Date());  
            /*获取今天的日期*/  
            System.out.println("今天的日期是："+calendar.get(Calendar.DAY_OF_MONTH));  
            /*获取十天之后的日期*/  
            calendar.clear();//避免继承当前系统的时间 
            calendar.set(Calendar.DAY_OF_MONTH, calendar.get(Calendar.DAY_OF_MONTH)+10);  
            System.out.println("十天之后的日期是："+calendar.get(Calendar.DAY_OF_MONTH));  
        }

#### 3、计算某个月的天数是多少 ####

/*计算某一个月的天数是多少*/  
        public void maxDay(int year,int month){   
            calendar.clear();  
            calendar.set(Calendar.YEAR, year);  
            calendar.set(Calendar.MONTH,month-1);//默认1月为0月 
            int day = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);  
            System.out.println(year+"年"+month+"月"+"的最大天数是："+day);  
        }  
        @Test  
        public void maxDayTest(){   
            maxDay(2017,9);  
        }

#### 4、计算某一天是该年或该月的第几个星期 ####

public void weekNum(int year,int month,int day){   
            calendar.clear();  
            calendar.set(Calendar.YEAR, year);  
            calendar.set(Calendar.MONTH,month-1);  
            calendar.set(Calendar.DAY_OF_MONTH, day);  
            /*计算某一天是该年的第几个星期*/  
            int weekOfYear = calendar.get(Calendar.WEEK_OF_YEAR);  
            System.out.println(year+"年"+month+"月"+day+"日是这年中的第"+weekOfYear+"个星期");  
            /*计算某一天是该月的第几个星期*/  
            int weekOfMonth= calendar.get(Calendar.WEEK_OF_MONTH);  
            System.out.println(year+"年"+month+"月"+day+"日是这个月中的第"+weekOfMonth+"个星期");  
        }  
        @Test  
        public void weekNumTest(){   
            weekNum(2017, 7, 8);  
        }

#### 5、计算一年中的第几星期是几号 ####

public void dayNum(int year,int week){   
        calendar.clear();  
        SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");  
        calendar.set(Calendar.YEAR, year);  
        calendar.set(Calendar.WEEK_OF_YEAR, week);  
        calendar.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);  
        System.out.println(df.format(calendar.getTime()));  
    }  
      
    @Test  
    public void dayNumTest(){   
        dayNum(2017,28);  
    }

#### 6、查询显示当前的后几天，前几天等 ####

public void add(int year,int month,int day,int num){   
            calendar.clear();  
            SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");  
            calendar.set(Calendar.YEAR, year);  
            calendar.set(Calendar.MONTH, month-1);  
            calendar.set(Calendar.DAY_OF_MONTH, day);  
            Date date=calendar.getTime();  
            calendar.add(Calendar.DATE, num);  
            date=calendar.getTime();  
            System.out.println(df.format(date));  
        }  
        /*使用场景比如，发找回密码邮件，设置一天后过期*/  
        @Test  
        public void addTest(){   
            add(2017,7,10,1);  
        }

[https_blog.csdn.net_tiantangdizhibuxiang_article_details_77429346]: https://blog.csdn.net/tiantangdizhibuxiang/article/details/77429346