java Calendar

/**  

      * 计算指定日期为当年第几周  

      * @param year      指定的年份  

      * @param month     指定的月份  

      * @param day       指定的日  

      * @return          指定日期为当年的第几周  

      */ 

    public static int caculateWeekOfYear(int year,int month,int day){  

         Calendar c = Calendar.getInstance();  

         c.set(Calendar.YEAR, year);  

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

         c.set(Calendar.DATE, day);  

         return c.get(Calendar.WEEK_OF_YEAR);  

     }  

        

     /**  

      * 获取本月第一天是星期几  

      * @return  

      */ 

     public static int getWeekOfFirstDay(Calendar c){  

         Calendar calendar = c;  

         calendar.set(Calendar.DAY_OF_MONTH, 1);  

         return calendar.get(Calendar.DAY_OF_WEEK);  

     }  

        

     /**  

      * 获取本月1号是该年的第几周  

      * @return  

      */ 

     public static int getMonthStartWeek(Calendar c){  

         Calendar calendar = c;  

         calendar.set(Calendar.DATE, 1);  

         return calendar.get(Calendar.WEEK_OF_YEAR);  

     }  

        

     /**  

      * 获取当天是该年的第几周  

      */ 

     public static int getCurrentWeekOfYear(){  

         Calendar calendar = Calendar.getInstance();  

         return calendar.get(Calendar.WEEK_OF_YEAR);  

     }  

        

     /**  

      * 获取上月的总天数  

      * @return  

      */ 

     public static int getLastMonthDays(Calendar c){  

         Calendar calendar = c;  

         calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH) - 1);  

         return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);  

     }  

        

     /**  

      * 获取指定月份的总天数  

      * @return  

      */ 

     public static int getCurrentMonthDays(int month){  

         Calendar c = Calendar.getInstance();  

         c.set(Calendar.MONTH, month);  

         return c.getActualMaximum(Calendar.DAY_OF_MONTH);  

     }  

        

     /**  

      * 获取指定年份有多少周  

      * @param year  

      * @return  

      */ 

     public static int getTotalWeekOfYear(int year){  

         Calendar c = Calendar.getInstance();  

         return c.getActualMaximum(Calendar.WEEK_OF_YEAR);  

     }  

        

     /**  

      * 判断指定月份是否是当前月  

      * @param month  

      * @return  

      */ 

     public static boolean isCurrentMonth(int month){  

         Calendar c = Calendar.getInstance();  

         return (c.get(Calendar.MONTH) == month)?true:false;  

     }  

        

     /**  

      * 计算指定的月份共有多少天  

      */ 

     public static int getTotalDaysOfMonth(int year, int month){  

         Calendar c = Calendar.getInstance();  

         c.set(Calendar.YEAR, year);  

         c.set(Calendar.MONTH, month);  

         c.set(Calendar.DATE, 1);  

         /**  

          * 计算这个月有多少天  

          */ 

         return c.getActualMaximum(Calendar.DAY_OF_MONTH);  

 } 

1.以上是各种方法

2.java 日期的加减

1. public class test1 {   
2.   
3.     public static void main(String[] args) {   
4.           Calendar c = Calendar.getInstance();   
5.           int year=c.get(Calendar.YEAR);   
6.              
7.   
8.             int month=c.get(Calendar.MONTH)+1;   
9.           int date=c.get(Calendar.DATE);   
10.           System.out.println("今天是"+year+"年"+month+"月"+date+"日");   
11.           System.out.println("是今年的第"+c.get(Calendar.DAY_OF_YEAR)+"天");   
12.           System.out.println("c.getTime()的結果: "+c.getTime());   
13.           System.out.println("new Date()的結果: "+new Date());   
14.           c.set(Calendar.DAY_OF_YEAR, date + 30);   
15.           System.out.println("17天后是"+c.getTime());   
16.       }   
17.   
18. }  

1.      
2.      public static Date getDateBefore(Date d, int day) {      
3.          Calendar now = Calendar.getInstance();      
4.          now.setTime(d);      
5.          now.set(Calendar.DATE, now.get(Calendar.DATE) - day);      
6.          return now.getTime();      
7.      }     
8.        
9.      public static Date getDateAfter(Date d, int day) {      
10.         Calendar now = Calendar.getInstance();      
11.          now.setTime(d);      
12.         now.set(Calendar.DATE, now.get(Calendar.DATE) + day);      
13.          return now.getTime();      
14.      }    

 

注意int month=c.get(Calendar.MONTH)+1哦，好像系统是从0开始计月份，到了12月就归零了。所以单独取月份时，要在后面加一才能得到当前的月份。



 calender日期加减后赋值给Date类型

Java代码

1. SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");   
2. String time=sdf.format(new Date());    
3. Calendar cd = Calendar.getInstance();   
4.   
5. try {   
6.     cd.setTime(sdf.parse(time));   
7. } catch (ParseException e) {               
8.     e.printStackTrace();   
9. }   
10.       cd.add(Calendar.DATE, 1);//增加一天        
11.        //cal.add(Calendar.DATE, -1);      //减一天    
12.        //cd.add(Calendar.MONTH, 1);//增加一月    
13.       Date date=cd.getTime();    
14.       System.out.println(sdf.format(date));