java 获得各种时间

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.context.i18n.LocaleContextHolder;

public class DateUtil {

 private static Log log = LogFactory.getLog(DateUtil.class);

 private static String defaultDatePattern = null;

 private static String timePattern = "HH:mm";

 

 public static Date getSystemTime() {
  Calendar now = Calendar.getInstance();
  return now.getTime();
  
 }

 public static synchronized String getDatePattern() {
  Locale locale = LocaleContextHolder.getLocale();
  try {
   defaultDatePattern = ResourceBundle.getBundle("yyyy-MM-dd",
     locale).getString("date.format");
  } catch (MissingResourceException mse) {
   defaultDatePattern = "yyyy-MM-dd";
  }

  return defaultDatePattern;
 }

 public static final String getDate(Date aDate) {
  SimpleDateFormat df = null;
  String returnValue = "";

  if (aDate != null) {
   df = new SimpleDateFormat(getDatePattern());
   returnValue = df.format(aDate);
  }

  return (returnValue);
 }

 public static final Date convertStringToDate(String aMask, String strDate) {
  SimpleDateFormat df = null;
  Date date = null;
  df = new SimpleDateFormat(aMask);

  if (log.isDebugEnabled()) {
   log.debug("converting '" + strDate + "' to date with mask '"
     + aMask + "'");
  }

  try {
   date = df.parse(strDate);
  } catch (ParseException pe) {
   log.error("ParseException: " + pe);
  }

  return (date);
 }

 public static String getTimeNow(Date theTime) {
  return getDateTime(timePattern, theTime);
 }

 public static Calendar getToday() throws ParseException {
  Date today = new Date();
  SimpleDateFormat df = new SimpleDateFormat(getDatePattern());

  // This seems like quite a hack (date -> string -> date),
  // but it works ;-)
  String todayAsString = df.format(today);
  Calendar cal = new GregorianCalendar();
  cal.setTime(convertStringToDate(todayAsString));

  return cal;
 }

 
 public static Date getMonday(Date date) {
  Calendar c = Calendar.getInstance();
  c.setTime(date);
  if (c.get(Calendar.DAY_OF_WEEK) == 1) {
   date = DateUtil.addDays(date, -7);
   c.setTime(date);
  }

  c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
  String mondayString = DateUtil.format(c.getTime(), "yyyy-MM-dd");
  mondayString = mondayString + " 00:00:00";
  return convertStringToDate("yyyy-MM-dd HH:mm:ss", mondayString);
 }

 
 public static Date getFriday(Date date) {
  Calendar c = Calendar.getInstance();
  c.setTime(date);
  c.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);
  String fridayString = format(c.getTime(), "yyyy-MM-dd");
  fridayString = fridayString + " 23:59:59";
  return convertStringToDate("yyyy-MM-dd HH:mm:ss", fridayString);

 }

 public static final String getDateTime(String aMask, Date aDate) {
  SimpleDateFormat df = null;
  String returnValue = "";

  if (aDate == null) {
   log.error("aDate is null!");
  } else {
   df = new SimpleDateFormat(aMask);
   returnValue = df.format(aDate);
  }

  return (returnValue);
 }

 public static final String convertDateToString(Date aDate) {
  return getDateTime(getDatePattern(), aDate);
 }

 public static Date convertStringToDate(String strDate) {
  Date aDate = null;

  try {
   if (log.isDebugEnabled()) {
    log.debug("converting date with pattern: " + getDatePattern());
   }

   aDate = convertStringToDate(getDatePattern(), strDate);
  } catch (Exception pe) {
   log.error("Could not convert '" + strDate
     + "' to a date, throwing exception");

  }

  return aDate;
 }

 public static int dayDiff(Date first, Date second) {

  long msPerDay = 1000 * 60 * 60 * 24;
  long diff = (first.getTime() / msPerDay)
    - (second.getTime() / msPerDay);
  
  Long convertLong = new Long(diff);
  return convertLong.intValue();
 }
 
 public static long dayDiffMilSecond(Date first, Date second) {

  long diff = first.getTime()-second.getTime();
  Long convertLong = new Long(diff);
  return convertLong;
 }

 
 public static String format(Date date, String pattern) {
  if(date==null) return "";
  SimpleDateFormat formatter = new SimpleDateFormat(pattern);
  return formatter.format(date);
 }

 static public final Date addDays(Date target, int days) {
  long msPerDay = 1000 * 60 * 60 * 24; // 一天的毫秒数
  long msTarget = target.getTime(); // 返回从一个特定的日期（1970。。）到现在经过的毫秒数。
  long msSum = msTarget + (msPerDay * days);
  Date result = new Date();
  result.setTime(msSum); // 根据毫秒设置日期
  return result;
 }
 
 public static Date beforeDays(Date target,int days)
 {
  long msPerDay = 1000 * 60 * 60 * 24; // 一天的毫秒数
  long msTarget = target.getTime(); // 返回从一个特定的日期（1970。。）到现在经过的毫秒数。
  long msSum = msTarget - (msPerDay * days);
  Date result = new Date();
  result.setTime(msSum); // 根据毫秒设置日期
  return result;
 }
   
 public static Date formatString(String time, String format){
  try{
   SimpleDateFormat formater = new SimpleDateFormat(format);
   return formater.parse(time);
  }catch(Exception e){
   return null;
  }
 }

 
 public static Date getFirstDateOfMonth(Date date){
  Calendar calendar = Calendar.getInstance();
  calendar.setTime(date);
  calendar.set(Calendar.DAY_OF_MONTH, 1);
  calendar.set(Calendar.HOUR_OF_DAY, 0);
  calendar.set(Calendar.MINUTE, 0);
  calendar.set(Calendar.SECOND, 0);
  return calendar.getTime();
 }
 
 
 public static Date getLastlyDateOfMonth(Date date){
  Calendar calendar = Calendar.getInstance();
  calendar.setTime(date);
  int month = calendar.get(Calendar.MONTH);
  calendar.set(Calendar.MONTH, month+1);
  calendar.set(Calendar.DAY_OF_MONTH, 1);
  calendar.set(Calendar.HOUR_OF_DAY, 23);
  calendar.set(Calendar.MINUTE, 59);
  calendar.set(Calendar.SECOND, 59);
  calendar.add(Calendar.DAY_OF_MONTH, -1);
  return calendar.getTime();
 }
 
 
 public static Date getFirstDateOfNextMonth(Date date){
  Calendar calendar = Calendar.getInstance();
  calendar.setTime(date);
  int month = calendar.get(Calendar.MONTH);
  calendar.set(Calendar.MONTH, month+1);
  calendar.set(Calendar.DAY_OF_MONTH, 1);
  calendar.set(Calendar.HOUR_OF_DAY, 0);
  calendar.set(Calendar.MINUTE, 0);
  calendar.set(Calendar.SECOND, 0);
  return calendar.getTime();
  
 }
 
 public static String getCurrentDayPath()
 {
  SimpleDateFormat sdf = new SimpleDateFormat("yyyy");
  Date now = new Date();
  String filePath = sdf.format(now) + "/";
  sdf = new SimpleDateFormat("MM");
  filePath += sdf.format(now) + "/";
  sdf = new SimpleDateFormat("dd");
  filePath += sdf.format(now) + "/";
  
  return filePath;
 }

}