java 时间运算 日期运算 日期加减 日期工具类

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import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class TimeUtil  {
	public static void main(String[] args) {
		TimeUtil  result = new TimeUtil ();
		System.out.println("相差日期为：" + result.daysSubtraction("2015-01-20", "2015-02-20"));
		System.out.println("相差月份为：" + result.monthSubtraction("2015-01", "2016-06"));
		System.out.println("相差年份为：" + result.yearSubtraction("2015", "2019"));
	}
	 public static int daysSubtraction(String dateStr1, String dateStr2) {
	  SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
	  SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd");
	  try {
	   dateStr1 = sdf.format(sdf2.parse(dateStr1));
	   dateStr2 = sdf.format(sdf2.parse(dateStr2));
	  } catch (ParseException e) {
	   e.printStackTrace();
	  }
	  int year1 = Integer.parseInt(dateStr1.substring(0, 4));
	  int month1 = Integer.parseInt(dateStr1.substring(4, 6));
	  int day1 = Integer.parseInt(dateStr1.substring(6, 8));
	  int year2 = Integer.parseInt(dateStr2.substring(0, 4));
	  int month2 = Integer.parseInt(dateStr2.substring(4, 6));
	  int day2 = Integer.parseInt(dateStr2.substring(6, 8));
	  Calendar c1 = Calendar.getInstance();
	  c1.set(Calendar.YEAR, year1);
	  c1.set(Calendar.MONTH, month1 - 1);
	  c1.set(Calendar.DAY_OF_MONTH, day1);
	  Calendar c2 = Calendar.getInstance();
	  c2.set(Calendar.YEAR, year2);
	  c2.set(Calendar.MONTH, month2 - 1);
	  c2.set(Calendar.DAY_OF_MONTH, day2);
	  long mills =
		  c1.getTimeInMillis() - c2.getTimeInMillis();//2678400000
	  int ss = (int)(mills/1000);//秒
	  int mm = (int)(ss/60);//分钟
	  int hh = (int)(mm/60);//小时
	  int dd = (int)(hh/24);//天
	  return Math.abs((int) (mills / 1000 / 3600 / 24));
	 }
	 
	 public static int monthSubtraction(String date1,String date2) {
		 SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM");
		try {
			Date d1 = sf.parse(date1);
			Date d2 = sf.parse(date2);
			Calendar cal1=Calendar.getInstance();
			cal1.setTime(d1);
			Calendar cal2=Calendar.getInstance();
			cal2.setTime(d2);
			return (Math.abs(cal2.get(1)-cal1.get(1)))*12+Math.abs((cal2.get(2)-cal1.get(2)));
		} catch (ParseException e) {
			e.printStackTrace();
		}
		return 0;
	 }
	 public static int yearSubtraction(String date1,String date2) {
		 SimpleDateFormat sf = new SimpleDateFormat("yyyy");
		 try {
			 Date d1 = sf.parse(date1);
			 Date d2 = sf.parse(date2);
			 Calendar cal1=Calendar.getInstance();
			 cal1.setTime(d1);
			 Calendar cal2=Calendar.getInstance();
			 cal2.setTime(d2);
			 return (cal2.get(1)-cal1.get(1));
		 } catch (ParseException e) {
			 e.printStackTrace();
		 }
		 return 0;
	 }
	
}