关于Java日期简单应用

//日期格式化
  Calendar calendar = Calendar.getInstance();
  SimpleDateFormat formatter1 = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
  String  myString1 =  formatter1.format(calendar.getTime());
  SimpleDateFormat formatter2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  String  myString2 =  formatter2.format(calendar.getTime());
  
  //字符串转换成日期格式,获得年月日
  String strDate = "2013/01/01";
  SimpleDateFormat formatter3 = new SimpleDateFormat("yyyy/MM/dd");
  Date date = formatter3.parse(strDate);
  Calendar myCalendar = Calendar.getInstance();
  myCalendar.setTime(date);
  //年
  System.out.println(myCalendar.get(Calendar.YEAR));
  //月(java中月份是从0开始的)
  System.out.println(myCalendar.get(Calendar.MONTH)+1);
  //日
  System.out.println(myCalendar.get(Calendar.DAY_OF_MONTH));
  
  //根据生日计算年龄
  String birth = "1983/12/24";
  SimpleDateFormat formatter4 = new SimpleDateFormat("yyyy/MM/dd");
  Date dateBirth= formatter4.parse(birth);    
  long day=(date.getTime()- dateBirth.getTime())/(24*60*60*1000) + 1;
  String year=new DecimalFormat("#").format(day/365);
  System.out.println(year);