javaのCalender（カレンダー）類

Calendar      getInstance()           :Calendar now = Calendar.getInstance();    

                     ：

  set(int year ,int month,int date)  

  set(int year ,int month,int date,int hour,int minute) 

  set(int year ,int month,int date,int hour,int minute,int second) 

        、  、         ：  

Now.get(Calendar.Month);      0    ，1      

  get(Calendar.DAY_OF_MONTH)         

  get(Calendar.DAY_OF_WEEK)           

  get(Calendar.DAY_OF_YEAR)           

  getTimeMillis()           

1.           
Calendar time=Calendar.getInstance(); 
time.clear(); 
time.set(Calendar.YEAR,year); 
time.set(Calendar.MONTH,i-1);//  ,Calendar       0             
int day=time.getActualMaximum(Calendar.DAY_OF_MONTH);//      
 ：   set    ，   clear  ，                
2.Calendar Date   
(1) Calendar   Date
Calendar cal=Calendar.getInstance();
Date date=cal.getTime();
(2) Date   Calendar
Date date=new Date();
Calendar cal=Calendar.getInstance();
cal.setTime(date);
3.         
Date date=new Date();
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
System.out.println(df.format(date));

4.         
   public int getDaysBetween (Calendar d1, Calendar d2){
      if (d1.after(d2)){  // swap dates so that d1 is start and d2 is end
           java.util.Calendar swap = d1;
           d1 = d2;
           d2 = swap;
      }
       int days = d2.get(Calendar.DAY_OF_YEAR) - d1.get(Calendar.DAY_OF_YEAR);
       int y2 = d2.get(Calendar.YEAR);
     if (d1.get(Calendar.YEAR) != y2){
           d1 = (Calendar) d1.clone();
           do{
             days += d1.getActualMaximum(Calendar.DAY_OF_YEAR);//         
               d1.add(Calendar.YEAR, 1);
          } while (d1.get(Calendar.YEAR) != y2);
      }
       return days;
    }