日期相关的工具类

package arithmetic;

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

/**
 * 有关日期时间的工具类
 * @author liujd
 *
 */
public class DataUtil {
	
	//格式化"yyyy-MM-dd"
	private static final String Date_Format_day = "yyyy-MM-dd";
	//格式化"yyyy-MM-dd HH:mm:ss"
	private static final String Date_Format_seconds = "yyyy-MM-dd HH:mm:ss";
	//格式化"yyyy-MM-dd HH:mm:ss"
	private static final String Date_Format_hms = "HH:mm:ss";
		
	/**
	 * 格式化"yyyy-MM-dd"
	 * 
	 * @param Date
	 * @return String
	 */
	public static String FormatToDay(Date dateNow) {
		SimpleDateFormat sdf = new SimpleDateFormat(Date_Format_day);
		return sdf.format(dateNow);
	}
	
	/**
	 * 格式化"yyyy-MM-dd HH:mm:ss"
	 * 
	 * @param Date
	 * @return String 
	 */
	public static String FormatToSeconds(Date dateNow) {
		SimpleDateFormat sdf = new SimpleDateFormat(Date_Format_seconds);
		return sdf.format(dateNow);
	}
	/**
	 * 格式化"HH:mm:ss"
	 * 
	 * @param Date
	 * @return String 
	 */
	public static String FormatHms(Date dateNow) {
		SimpleDateFormat sdf = new SimpleDateFormat(Date_Format_hms);
		return sdf.format(dateNow);
	}
	/**
	 * 获取年 月 日  时 分 秒
	 * @param String Date
	 * @return int
	 */
	@SuppressWarnings("deprecation")
	public static int getByType(Date dateNow,String type) {
		int result = 0;
		switch (type) {
		case "year":
			result = dateNow.getYear() + 1900;
			break;
		case "month":
			result = dateNow.getMonth() + 1;
			break;
		case "day":
			result = dateNow.getDate();	
			break;
		case "hours":
			result = dateNow.getHours();
			break;
		case "minutes":
			result = dateNow.getMinutes();
			break;
		case "seconds":
			result = dateNow.getSeconds();
			break;
		default:
			result = 0;
			break;
		}
		return result;	
	}
	
	/**
	 * 将日期转换为字符串
	 * 
	 * @param Date
	 * @return String
	 */
	@SuppressWarnings("deprecation")
	public static String DateToString(Date dateNow) {
		return dateNow.toLocaleString();
	}
	
	/**
	 * 将时间格式是 "yyyy-MM-dd HH:mm:ss"的字符串转换为日期
	 * @param String
	 * @return Date
	 */
	public static Date StringToDate1(String dateString) {
		try {
			SimpleDateFormat sdf = new SimpleDateFormat(Date_Format_seconds);
			return sdf.parse(dateString);
		} catch (ParseException e) {
			e.printStackTrace();
			return null;
		}
	}
	/**
	 * 将时间格式是 "yyyy-MM-dd"的字符串转换为日期
	 * @param String
	 * @return Date
	 */
	public static Date StringToDate2(String dateString)  {
		try {
		SimpleDateFormat sdf = new SimpleDateFormat(Date_Format_day);
			return sdf.parse(dateString);
		} catch (ParseException e) {
			e.printStackTrace();
			return null;
		}
		
	}
	/**
	 * 获取两个日期相差的天数
	 * @param Date Date
	 * @return int
	 */
	public static int diffOfTwo(Date date1 , Date date2) {
		long time1 = date1.getTime();
		long time2 = date2.getTime();
		int diff = (int)((time1-time2)/60*60*24*1000);
		return diff;
	}
	/**
	 * 指定日期加上天数
	 * @param Date int
	 * @return Date
	 */
	public static Date addDate(Date date , int day) {
		Calendar c = Calendar.getInstance();
		c.setTime(date);
		long timeInMillis = c.getTimeInMillis();
		c.setTimeInMillis(timeInMillis+(((long)day)*24*60*60*1000));
		return c.getTime();
	}
	/**
	 * 指定日期减去天数
	 * @param Date int
	 * @return Date
	 */
	public static Date subDate(Date date , int day) {
		Calendar c = Calendar.getInstance();
		c.setTime(date);
		long timeInMillis = c.getTimeInMillis();
		c.setTimeInMillis(timeInMillis-(((long)day)*24*60*60*1000));
		return c.getTime();
	}
	/**
	 * 获取年
	 * @param Date
	 * @return int
	 */
	public static int getYear(Date date) {
		if(date == null) {
			date = new Date();
		}
		Calendar c = Calendar.getInstance();
		c.setTime(date);
		return c.get(Calendar.YEAR);
	}
	/**
	 * 获取月
	 * @param Date
	 * @return int
	 */
	public static int getMonth(Date date) {
		if(date == null) {
			date = new Date();
		}
		Calendar c = Calendar.getInstance();
		c.setTime(date);
		return c.get(Calendar.MONTH) + 1;
	}
	/**
	 * 获取日
	 * @param Date
	 * @return int
	 */
	public static int getDay(Date date) {
		if(date == null) {
			date = new Date();
		}
		Calendar c = Calendar.getInstance();
		c.setTime(date);
		return c.get(Calendar.DAY_OF_MONTH);
	}
	/**
	 * 获取星期
	 * @param Date
	 * @return int
	 */
	public static int getWeek(Date date) {
		if(date == null) {
			date = new Date();
		}
		Calendar c = Calendar.getInstance();
		c.setTime(date);
		int week = c.get(Calendar.DAY_OF_WEEK) - 1;
		if(week == 0) {
			return 7;
		}else {
			return week;
		}
	}
	/**
	 * 判断字符串是否是时间格式
	 * 默认时间格式是 "yyyy-MM-dd"
	 * @param string
	 * @return boolean
	 */
	public static boolean isDateFormat(String dateString) {
		SimpleDateFormat sdf = new SimpleDateFormat(Date_Format_day);
		if(isEmpty(dateString)) {
			return false;
		}
		try {
			sdf.parse(dateString);
			return true;
		} catch (ParseException e) {
			e.printStackTrace();
			return false;
		}
	}
	/**
	 * 判断字符串是否为空
	 * @param string
	 * @return boolean
	 */
	public static boolean isEmpty(String str) {
		return str.trim().length() == 0 ? true : false;
	}
	public static void main(String[] args) {
		System.out.println(FormatToDay(new Date()));;
		System.out.println(FormatToSeconds(new Date()));;
	}
	
}

暂时就想到这些  以后补上