本人之前做的项目中积累常用的时间方法，贴出来与大家共享，如果哪里有错误或更有效的方法请尽管拍砖！

package com.dc.util.date;
import java.sql.Timestamp;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Collection;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.List;
import java.util.Set;

import com.dc.util.collection.CollectionUtil;

public class TimeUtil {
// 用来全局控制 上一周，本周，下一周的周数变化
private int weeks = 0;
private int MaxDate;// 一月最大天数
private int MaxYear;// 一年最大天数

//字符串转为Timestamp
public static String getTimestampString(Timestamp d){
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
return format.format(d);
}


public static Timestamp removeHHMMSS(Timestamp d){
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
try {
return new Timestamp(format.parse(format.format(d)).getTime());
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

//加时间秒为单位
public static Timestamp addTimeForTimestamp(Timestamp d,long sec){
sec =  d.getTime()/1000+sec;
Date date = new Date(d.getTime());
date.setTime(sec * 1000);
d.setTime(date.getTime());
return d;
}

// 获取当天时间
public static String getNowTimeString() {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
return sdf.format(new Date());
}

public static String getTimestampPart(Timestamp d,String format){
SimpleDateFormat sformat = new SimpleDateFormat(format);
return sformat.format(d);
}

//字符串转为Timestamp
public static Timestamp getTimestamp(String d,String format){
if(format==null){
   format = "yyyy-MM-dd HH:mm:ss";
}
SimpleDateFormat sformat = new SimpleDateFormat(format);
try {
return new Timestamp(sformat.parse(d).getTime());
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}


/**
* 获得某年第一天星期几
* @param year
* @return
*/
public int getFirstDayOfYear(String year) {
//求某月的第一天星期几
SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd");
Date date = null;
try {
date = f.parse(year + "-1-1");
} catch (ParseException e) {
e.printStackTrace();
}
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
int firstWeek = calendar.get(Calendar.DAY_OF_WEEK);// (Calendar中1-星期天，2-星期一，3-星期二，4-星期三，5-星期四，6-星期五，7-星期六)
        return firstWeek;
}

/**
* 获得某年第一个星期X是几号
* @param year
* @param i 0 星期天 1星期一 .......
* @return
*/
public static Timestamp getFirstWeekDayOfYear(String year,Integer[] weeks) {
Collection<Integer> coll = CollectionUtil.arrayToCollection(weeks);
//求某月的第一天星期几
SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd");
Date date=null;
try {
date = f.parse(year + "-1-1");
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
int firstWeek = -1;
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
do{
    firstWeek = calendar.get(Calendar.DAY_OF_WEEK) - 1;
    if(!coll.contains(firstWeek)){
    calendar.setTime(new Date(date.getTime()+(60*60*24*1000)));
    }else{
    return new Timestamp(calendar.getTime().getTime());
    }
        }while(true);
}


/**
* 指定日期的下几天
* @param d 格式 yyyy-MM-dd HH:mm:ss
* @param c 下几天
* @return
*/
public static String getNextDate(String d,int c){
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
try {
  Date date = format.parse(d);
  Long myTime=(date.getTime()/1000)+(60*60*24)*c;
  date.setTime(myTime*1000);
  return format.format(date);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}

/**
* 指定日期的下几天
* @param d 格式 yyyy-MM-dd HH:mm:ss
* @param c 下几天
* @return
*/
public static String getNextDate(Date d,int c,String format){
if(format==null){
format = "yyyy-MM-dd HH:mm:ss";
}
SimpleDateFormat sdformat = new SimpleDateFormat(format);
    Date date = d;
    Long myTime=(date.getTime()/1000)+(60*60*24)*c;
    date.setTime(myTime*1000);
    return sdformat.format(date);
}

/**
* 指定日期的下几天
* @param d 格式 yyyy-MM-dd HH:mm:ss
* @param c 下几天
* @return
*/
public static Timestamp getNextDate(Timestamp date,int c){
try {
  Long myTime=(date.getTime()/1000)+(60*60*24)*c;
  date.setTime(myTime*1000);
  return date;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

/**
* 得到某天的下一天星期几
* @param d 某一日期
* @param c 偏移天数
* @return 日期包含星期
*/
public static String getNextDateWeek(String d,int c){
final String dayNames[] = {"星期日","星期一","星期二","星期三","星期四","星期五","星期六"};
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Calendar cal = Calendar.getInstance();
try {
  Date date = format.parse(d);
  Long myTime=(date.getTime()/1000)+(60*60*24)*c;
  date.setTime(myTime*1000);
  cal.setTime(date);
  return format.format(date) + " " + dayNames[cal.get(Calendar.DAY_OF_WEEK)-1];
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}

/**
* 获得指定星期范围内的日期集合
* @param d 某一日期
* @param c 偏移天数
* @param weeks 一个或一个以目的星期
* @param jishu 是否计数
* @return
*/
public static List<String> getWeekOfRange(String d,int c,Set<String> weeks,boolean jishu){
List<String> dates = new ArrayList<String>();
for(int i=0;jishu?dates.size()<c:i<c;i++){
String date = getNextDateWeek(d,i);
if(weeks.contains(date.split(" ")[2])){
dates.add(date);
}
}
return dates;
}


/**
* 得到二个日期间的间隔天数
*/
public static String getTwoDay(String sj1, String sj2) {
SimpleDateFormat myFormatter = new SimpleDateFormat("yyyy-MM-dd");
long day = 0;
try {
java.util.Date date = myFormatter.parse(sj1);
java.util.Date mydate = myFormatter.parse(sj2);
day = (date.getTime() - mydate.getTime()) / (24 * 60 * 60 * 1000);
} catch (Exception e) {
return "";
}
return day + "";
}

/**
* 根据一个日期，返回是星期几的字符串
*
* @param sdate
* @return
*/
public static String getWeek(String sdate) {
// 再转换为时间
Date date = TimeUtil.strToDate(sdate);
Calendar c = Calendar.getInstance();
c.setTime(date);
// int hour=c.get(Calendar.DAY_OF_WEEK);
// hour中存的就是星期几了，其范围 1~7
// 1=星期日 7=星期六，其他类推
return new SimpleDateFormat("EEEE").format(c.getTime());
}

/**
* 将短时间格式字符串转换为时间 yyyy-MM-dd
*
* @param strDate
* @return
*/
public static Date strToDate(String strDate) {
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
ParsePosition pos = new ParsePosition(0);
Date strtodate = formatter.parse(strDate, pos);
return strtodate;
}


/**
* 两个时间之间的天数
*
* @param date1
* @param date2
* @return
*/
public static long getDays(String date1, String date2) {
if (date1 == null || date1.equals(""))
return 0;
if (date2 == null || date2.equals(""))
return 0;
// 转换为标准时间
SimpleDateFormat myFormatter = new SimpleDateFormat("yyyy-MM-dd");
java.util.Date date = null;
java.util.Date mydate = null;
try {
date = myFormatter.parse(date1);
mydate = myFormatter.parse(date2);
} catch (Exception e) {
}
long day = (date.getTime() - mydate.getTime()) / (24 * 60 * 60 * 1000);
return day;
}

// 计算当月最后一天,返回字符串
public String getDefaultDay() {
String str = "";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Calendar lastDate = Calendar.getInstance();
lastDate.set(Calendar.DATE, 1);// 设为当前月的1号
lastDate.add(Calendar.MONTH, 1);// 加一个月，变为下月的1号
lastDate.add(Calendar.DATE, -1);// 减去一天，变为当月最后一天

str = sdf.format(lastDate.getTime());
return str;
}

// 上月第一天
public String getPreviousMonthFirst() {
String str = "";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Calendar lastDate = Calendar.getInstance();
lastDate.set(Calendar.DATE, 1);// 设为当前月的1号
lastDate.add(Calendar.MONTH, -1);// 减一个月，变为下月的1号
// lastDate.add(Calendar.DATE,-1);//减去一天，变为当月最后一天

str = sdf.format(lastDate.getTime());
return str;
}

// 获取当月第一天
public String getFirstDayOfMonth() {
String str = "";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Calendar lastDate = Calendar.getInstance();
lastDate.set(Calendar.DATE, 1);// 设为当前月的1号
str = sdf.format(lastDate.getTime());
return str;
}



// 获得本周星期日的日期
public String getCurrentWeekday() {
weeks = 0;
int mondayPlus = this.getMondayPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE, mondayPlus + 6);
Date monday = currentDate.getTime();

DateFormat df = DateFormat.getDateInstance();
String preMonday = df.format(monday);
return preMonday;
}

// 获取当天时间
public String getNowTime(String dateformat) {
Date now = new Date();
SimpleDateFormat dateFormat = new SimpleDateFormat(dateformat);// 可以方便地修改日期格式
String hehe = dateFormat.format(now);
return hehe;
}

// 获得当前日期与本周日相差的天数
private int getMondayPlus() {
Calendar cd = Calendar.getInstance();
// 获得今天是一周的第几天，星期日是第一天，星期二是第二天......
int dayOfWeek = cd.get(Calendar.DAY_OF_WEEK) - 1; // 因为按中国礼拜一作为第一天所以这里减1
if (dayOfWeek == 1) {
return 0;
} else {
return 1 - dayOfWeek;
}
}

// 获得本周一的日期
public String getMondayOFWeek() {
weeks = 0;
int mondayPlus = this.getMondayPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE, mondayPlus);
Date monday = currentDate.getTime();

DateFormat df = DateFormat.getDateInstance();
String preMonday = df.format(monday);
return preMonday;
}

// 获得相应周的周六的日期
public String getSaturday() {
int mondayPlus = this.getMondayPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE, mondayPlus + 7 * weeks + 6);
Date monday = currentDate.getTime();
DateFormat df = DateFormat.getDateInstance();
String preMonday = df.format(monday);
return preMonday;
}

// 获得上周星期日的日期
public String getPreviousWeekSunday() {
weeks = 0;
weeks--;
int mondayPlus = this.getMondayPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE, mondayPlus + weeks);
Date monday = currentDate.getTime();
DateFormat df = DateFormat.getDateInstance();
String preMonday = df.format(monday);
return preMonday;
}

// 获得上周星期一的日期
public String getPreviousWeekday() {
weeks--;
int mondayPlus = this.getMondayPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE, mondayPlus + 7 * weeks);
Date monday = currentDate.getTime();
DateFormat df = DateFormat.getDateInstance();
String preMonday = df.format(monday);
return preMonday;
}

// 获得下周星期一的日期
public String getNextMonday() {
weeks++;
int mondayPlus = this.getMondayPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE, mondayPlus + 7);
Date monday = currentDate.getTime();
DateFormat df = DateFormat.getDateInstance();
String preMonday = df.format(monday);
return preMonday;
}

// 获得下周星期日的日期
public String getNextSunday() {

int mondayPlus = this.getMondayPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE, mondayPlus + 7 + 6);
Date monday = currentDate.getTime();
DateFormat df = DateFormat.getDateInstance();
String preMonday = df.format(monday);
return preMonday;
}

private int getMonthPlus() {
Calendar cd = Calendar.getInstance();
int monthOfNumber = cd.get(Calendar.DAY_OF_MONTH);
cd.set(Calendar.DATE, 1);// 把日期设置为当月第一天
cd.roll(Calendar.DATE, -1);// 日期回滚一天，也就是最后一天
MaxDate = cd.get(Calendar.DATE);
if (monthOfNumber == 1) {
return -MaxDate;
} else {
return 1 - monthOfNumber;
}
}

// 获得上月最后一天的日期
public String getPreviousMonthEnd() {
String str = "";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Calendar lastDate = Calendar.getInstance();
lastDate.add(Calendar.MONTH, -1);// 减一个月
lastDate.set(Calendar.DATE, 1);// 把日期设置为当月第一天
lastDate.roll(Calendar.DATE, -1);// 日期回滚一天，也就是本月最后一天
str = sdf.format(lastDate.getTime());
return str;
}

// 获得下个月第一天的日期
public String getNextMonthFirst() {
String str = "";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Calendar lastDate = Calendar.getInstance();
lastDate.add(Calendar.MONTH, 1);// 减一个月
lastDate.set(Calendar.DATE, 1);// 把日期设置为当月第一天
str = sdf.format(lastDate.getTime());
return str;
}

// 获得下个月最后一天的日期
public String getNextMonthEnd() {
String str = "";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Calendar lastDate = Calendar.getInstance();
lastDate.add(Calendar.MONTH, 1);// 加一个月
lastDate.set(Calendar.DATE, 1);// 把日期设置为当月第一天
lastDate.roll(Calendar.DATE, -1);// 日期回滚一天，也就是本月最后一天
str = sdf.format(lastDate.getTime());
return str;
}

// 获得明年最后一天的日期
public String getNextYearEnd() {
String str = "";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Calendar lastDate = Calendar.getInstance();
lastDate.add(Calendar.YEAR, 1);// 加一个年
lastDate.set(Calendar.DAY_OF_YEAR, 1);
lastDate.roll(Calendar.DAY_OF_YEAR, -1);
str = sdf.format(lastDate.getTime());
return str;
}

// 获得明年第一天的日期
public String getNextYearFirst() {
String str = "";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Calendar lastDate = Calendar.getInstance();
lastDate.add(Calendar.YEAR, 1);// 加一个年
lastDate.set(Calendar.DAY_OF_YEAR, 1);
str = sdf.format(lastDate.getTime());
return str;

}

// 获得本年有多少天
private int getMaxYear() {
Calendar cd = Calendar.getInstance();
cd.set(Calendar.DAY_OF_YEAR, 1);// 把日期设为当年第一天
cd.roll(Calendar.DAY_OF_YEAR, -1);// 把日期回滚一天。
int MaxYear = cd.get(Calendar.DAY_OF_YEAR);
return MaxYear;
}

private int getYearPlus() {
Calendar cd = Calendar.getInstance();
int yearOfNumber = cd.get(Calendar.DAY_OF_YEAR);// 获得当天是一年中的第几天
cd.set(Calendar.DAY_OF_YEAR, 1);// 把日期设为当年第一天
cd.roll(Calendar.DAY_OF_YEAR, -1);// 把日期回滚一天。
int MaxYear = cd.get(Calendar.DAY_OF_YEAR);
if (yearOfNumber == 1) {
return -MaxYear;
} else {
return 1 - yearOfNumber;
}
}

// 获得本年第一天的日期
public String getCurrentYearFirst() {
int yearPlus = this.getYearPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE, yearPlus);
Date yearDay = currentDate.getTime();
DateFormat df = DateFormat.getDateInstance();
String preYearDay = df.format(yearDay);
return preYearDay;
}

// 获得本年最后一天的日期 *
public String getCurrentYearEnd() {
Date date = new Date();
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy");// 可以方便地修改日期格式
String years = dateFormat.format(date);
return years + "-12-31";
}

// 获得上年第一天的日期 *
public String getPreviousYearFirst() {
Date date = new Date();
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy");// 可以方便地修改日期格式
String years = dateFormat.format(date);
int years_value = Integer.parseInt(years);
years_value--;
return years_value + "-1-1";
}

// 获得上年最后一天的日期
public String getPreviousYearEnd() {
weeks--;
int yearPlus = this.getYearPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE, yearPlus + MaxYear * weeks
+ (MaxYear - 1));
Date yearDay = currentDate.getTime();
DateFormat df = DateFormat.getDateInstance();
String preYearDay = df.format(yearDay);
getThisSeasonTime(11);
return preYearDay;
}
/**
*以开始时间为参数进行计算
* @param beginDate
* @return
*/
public static Timestamp findNextDayOfWeek(Timestamp beginDate,Set<String> set){
Timestamp date = null;
Timestamp _beginDate = (Timestamp) beginDate.clone();
do{
          String week = getNextDateWeek(getTimestampString(_beginDate), 1);
          date = getNextDate(_beginDate, 1);
          if(set.contains(week.split(" ")[2])){
          return date;
          }
}while(true);
}







// 获得本季度
public String getThisSeasonTime(int month) {
int array[][] = { { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 }, { 10, 11, 12 } };
int season = 1;
if (month >= 1 && month <= 3) {
season = 1;
}
if (month >= 4 && month <= 6) {
season = 2;
}
if (month >= 7 && month <= 9) {
season = 3;
}
if (month >= 10 && month <= 12) {
season = 4;
}
int start_month = array[season - 1][0];
int end_month = array[season - 1][2];

Date date = new Date();
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy");// 可以方便地修改日期格式
String years = dateFormat.format(date);
int years_value = Integer.parseInt(years);

int start_days = 1;// years+"-"+String.valueOf(start_month)+"-1";//getLastDayOfMonth(years_value,start_month);
int end_days = getLastDayOfMonth(years_value, end_month);
String seasonDate = years_value + "-" + start_month + "-" + start_days
+ ";" + years_value + "-" + end_month + "-" + end_days;
return seasonDate;

}

/**
* 获取某年某月的最后一天
*
* @param year
*            年
* @param month
*            月
* @return 最后一天
*/
private int getLastDayOfMonth(int year, int month) {
if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8
|| month == 10 || month == 12) {
return 31;
}
if (month == 4 || month == 6 || month == 9 || month == 11) {
return 30;
}
if (month == 2) {
if (isLeapYear(year)) {
return 29;
} else {
return 28;
}
}
return 0;
}

/**
* 是否闰年
*
* @param year
*            年
* @return
*/
public  boolean isLeapYear(int year) {
return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
}

/**
* @param args
*/
public static void main(String[] args) {
TimeUtil tt = new TimeUtil();
// System.out.println("获取当天日期:" + tt.getNowTime("yyyy-MM-dd"));
// System.out.println("获取明天日期:"+ tt.getNextDate("2011-4-30 00:00:00",1));
// System.out.println("获取明天星期几:"+ tt.getNextDateWeek("2011-8-1 00:00:00",1));
// System.out.println("获取本周一日期:" + tt.getMondayOFWeek());
// System.out.println("获取本周日的日期~:" + tt.getCurrentWeekday());
// System.out.println("获取上周一日期:" + tt.getPreviousWeekday());
// System.out.println("获取上周日日期:" + tt.getPreviousWeekSunday());
// System.out.println("获取下周一日期:" + tt.getNextMonday());
// System.out.println("获取下周日日期:" + tt.getNextSunday());
// System.out.println("获得相应周的周六的日期:" + tt.getNowTime("yyyy-MM-dd"));
// System.out.println("获取本月第一天日期:" + tt.getFirstDayOfMonth());
// System.out.println("获取本月最后一天日期:" + tt.getDefaultDay());
// System.out.println("获取上月第一天日期:" + tt.getPreviousMonthFirst());
// System.out.println("获取上月最后一天的日期:" + tt.getPreviousMonthEnd());
// System.out.println("获取下月第一天日期:" + tt.getNextMonthFirst());
// System.out.println("获取下月最后一天日期:" + tt.getNextMonthEnd());
// System.out.println("获取本年的第一天日期:" + tt.getCurrentYearFirst());
// System.out.println("获取本年最后一天日期:" + tt.getCurrentYearEnd());
// System.out.println("获取去年的第一天日期:" + tt.getPreviousYearFirst());
//System.out.println("获取去年的最后一天日期:" + tt.getPreviousYearEnd());
//System.out.println("获取明年第一天日期:" + tt.getNextYearFirst());
//System.out.println("今年有多少天"+tt.getCurrentYearEnd());
// System.out.println("获取明年最后一天日期:" + tt.getNextYearEnd());
// System.out.println("获取本季度第一天到最后一天:" + tt.getThisSeasonTime(11));
     System.out.println("获取两个日期之间间隔天数2010-12-31~2010-9-14:" + TimeUtil.getTwoDay("2011-09-20 14:47:17", "2011-09-19 14:37:172011-09-19 14:37:17"));
// System.out.println("获得某年第一个星期X是几号" + tt.getFirstWeekDayOfYear("2011",new Integer[]{2,4,0}));
         System.out.println("某天的下一天" +tt.getNextDate(new Date(), -1,"yyyy-MM-dd 21:55:00"));
}

}