工具类2：DateUtil

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

/**
* 时间处理函数
*
* @20080509 15：50
*/
public class DateUtil {

private static final String DEFAULT_PATTERN = "yyyy-MM-dd HH:mm:ss";

public static final String TIME_YEAR = "yyyy";

public static final String TIME_MONEN = "MM";

public static final String TIME_DAY = "dd";

public static String getDate(String interval, Date starttime, String pattern) {
Calendar temp = Calendar.getInstance(TimeZone.getDefault());
temp.setTime(starttime);
temp.add(temp.MONTH, Integer.parseInt(interval));
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
return sdf.format(temp.getTime());
}

/**
* 将字符串类型转换为时间类型
*
* @return
*/
public static Date str2Date(String str) {
Date d = null;
SimpleDateFormat sdf = new SimpleDateFormat(DEFAULT_PATTERN);
try {
d = sdf.parse(str);
} catch (Exception e) {
e.printStackTrace();
}
return d;
}

public static Date str2Date(String str, String pattern) {
Date d = null;
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
try {
d = sdf.parse(str);
} catch (Exception e) {
e.printStackTrace();
}
return d;
}

/**
* 将时间格式化
*
* @return
*/
public static Date DatePattern(Date date) {
SimpleDateFormat sdf = new SimpleDateFormat(DEFAULT_PATTERN);
try {
String dd = sdf.format(date);
date = str2Date(dd);
} catch (Exception e) {
e.printStackTrace();
}
return date;
}

/**
* 将时间格式化
*/
public static Date DatePattern(Date date, String pattern) {
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
try {
String dd = sdf.format(date);
date = str2Date(dd, pattern);
} catch (Exception e) {
e.printStackTrace();
}
return date;
}

public static String date2Str(Date date) {
SimpleDateFormat sdf = new SimpleDateFormat(DEFAULT_PATTERN);
return sdf.format(date);
}

public static String date2Str(Date date, String format) {
SimpleDateFormat sdf = new SimpleDateFormat(format);
return sdf.format(date);
}

/**
* 获取昨天
*
* @param date
* @return
* @throws Exception
*/
public static Date getLastDate(Date date) {
Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
calendar.setTime(date);

calendar.add(calendar.DATE, -1);

return str2Date(date2Str(calendar.getTime()));
}
/**
* 获取前几天
* @param date
* @return
*/
public static Date getBeforeDate(Date date,int dates) {
Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
calendar.setTime(date);

calendar.add(calendar.DATE, -dates);

return str2Date(date2Str(calendar.getTime()));
}

/**
* 获取上周第一天（周一）
*
* @param date
* @return
* @throws Exception
*/
public static Date getLastWeekStart(Date date) {
Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
calendar.setTime(date);
int i = calendar.get(calendar.DAY_OF_WEEK) - 1;
int startnum = 0;
if (i == 0) {
startnum = 7 + 6;
} else {
startnum = 7 + i - 1;
}
calendar.add(calendar.DATE, -startnum);

return str2Date(date2Str(calendar.getTime()));
}

/**
* 获取上周最后一天（周末）
*
* @param date
* @return
* @throws Exception
*/
public static Date getLastWeekEnd(Date date) {
Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
calendar.setTime(date);
int i = calendar.get(calendar.DAY_OF_WEEK) - 1;
int endnum = 0;
if (i == 0) {
endnum = 7;
} else {
endnum = i;
}
calendar.add(calendar.DATE, -(endnum - 1));

return str2Date(date2Str(calendar.getTime()));
}

/**
* 根据年和月得到天数
* @param num 月
* @param year 年
* @return
*/
public static int getday(int num,int year){
if(num==1 || num==3 || num==5 || num==7 || num==8 || num==10 || num==12){
return 31;
}else if(num==2){
//判断是否为闰年
if(year%400==0 || (year%4==0 && year%100!=0)){
return 29;
}else{
return 28;
}

}else{
return 30;
}
}
/*
* 计算当前日期距离下个月还有多少天
*/
public static int getdaymis(Date time){
int year = Integer.parseInt(
new SimpleDateFormat(TIME_YEAR).format(time));//年

int mm = Integer.parseInt(
new SimpleDateFormat(TIME_MONEN).format(time));//月

int dd = Integer.parseInt(
new SimpleDateFormat(TIME_DAY).format(time));//日


//获取当前年月的总天数
int sdd = getday(mm,year);

return sdd-dd;


}
/**
* 日期转秒数
* @param dateString
* @return
*/
public static long getTime(String dateString) {
    long time = 0;
    try {
    Date ret = null;
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    ret = sdf.parse(dateString);
    time = ret.getTime()/1000;
    } catch (Exception e) {

    }
    return time;
    }


/**
* 精确计算时间差，精确到日
* @param fistill 起始日期
* @param nowtime 结束日期
* @param type type为1返回年月日（如：2年3个月零5天） 否则返回总的天数
* @return
*/
public static String patienage(Date fistill,Date nowtime,Integer type){

int fyear = Integer.parseInt(
new SimpleDateFormat(TIME_YEAR).format(fistill));//起始年

int fmm = Integer.parseInt(
new SimpleDateFormat(TIME_MONEN).format(fistill));//起始月

int fdd = Integer.parseInt(
new SimpleDateFormat(TIME_DAY).format(fistill));//起始日


int nyear = Integer.parseInt(
new SimpleDateFormat(TIME_YEAR).format(nowtime));//结束年

int nmm = Integer.parseInt(
new SimpleDateFormat(TIME_MONEN).format(nowtime));//结束月

int ndd = Integer.parseInt(
new SimpleDateFormat(TIME_DAY).format(nowtime));//结束日

int cyear = nyear - fyear;
int cmm = nmm - fmm;
int cdd = ndd - fdd;


int zyear = 0;
int zmm = 0;
int zdd = 0;

int countddd = 0;  //年月日累计天数

if(cdd<0){
if(cmm<0){
zyear = cyear - 1;
zmm = (cmm + 12)-1;
int dd = getday(zmm,nyear-1);
zdd = dd + cdd;


countddd = zyear*365+zmm*30+zdd;

}else if(cmm==0){
zyear = cyear - 1;
zmm = 12-1;
int dd = getday(zmm,nyear-1);
zdd = dd + cdd;

countddd = zyear*365+zmm*30+zdd;

}else{
zyear = cyear;
zmm = cmm - 1;
int dd = getday(zmm,nyear);
zdd = dd + cdd;

countddd = zyear*365+zmm*30+zdd;

}
}else if(cdd==0){
if(cmm<0){
zyear = cyear - 1;
zmm = cmm + 12;
zdd = 0;

countddd = zyear*365+zmm*30;

}else if(cmm==0){
zyear = cyear;
zmm = 0;
zdd = 0;

countddd = zyear*365+zmm*30;

}else{
zyear = cyear;
zmm = cmm;
zdd = 0;

countddd = zyear*365+zmm*30;
}
}else{
if(cmm<0){
zyear = cyear - 1;
zmm = cmm + 12;
zdd = cdd;

countddd = zyear*365+zmm*30+zdd;
}else if(cmm==0){
zyear = cyear;
zmm = 0;
zdd = cdd;

countddd = zyear*365+zmm*30+zdd;
}else{
zyear = cyear;
zmm = cmm;
zdd = cdd;

countddd = zyear*365+zmm*30+zdd;
}
}
String ptime = null;

if(zdd!=0){
if(zmm!=0){
if(zyear!=0){
ptime = zyear+"年"+zmm+"个月"+"零"+zdd+"天";
}else{
ptime = zmm+"个月"+"零"+zdd+"天";
}
}else{
if(zyear!=0){
ptime = zyear+"年"+"零"+zdd+"天";
}else{
ptime = zdd+"天";
}
}
}else{
if(zmm!=0){
if(zyear!=0){
ptime = zyear+"年"+zmm+"个月";
}else{
ptime = zmm+"个月";
}
}else{
if(zyear!=0){
ptime = zyear+"年";
}else{
ptime = null;
}
}
}
if(type==1){
return ptime;   //返回年月日（如：2年3个月零5天）
}else{
return String.valueOf(countddd);  //返回总天数
}


}
/**
* 得到月数
* @param year 年数差
* @param month 月数差
* @return
*/
public static int getCmm(Integer year,Integer month){
int zmm = 0;
if(month < 0){
zmm = (month + 12)+(year-1)*12;
}else if(month == 0){
zmm = year*12;
}else{
zmm = year*12+month;
}
return zmm;
}



/**
* 改更现在时间
*/
public static Date changeDate(String type, int value) {
Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
if (type.equals("month")) {
calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH) + value);
} else if (type.equals("date")) {
calendar.set(Calendar.DATE, calendar.get(Calendar.DATE) + value);
}
return calendar.getTime();
}

/**
* 更改时间
*/
public static Date changeDate(Date date, String type, int value) {
if (date != null) {
// Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
Calendar calendar = new GregorianCalendar();
calendar.setTime(date);
// Calendar calendar = Calendar.
if (type.equals("month")) {
calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH) + value);
} else if (type.equals("date")) {
calendar.set(Calendar.DATE, calendar.get(Calendar.DATE) + value);
} else if (type.endsWith("year")) {
calendar.set(Calendar.YEAR, calendar.get(Calendar.YEAR) + value);
}
return calendar.getTime();
}
return null;
}

/**
* haoxw 比较时间是否在这两个时间点之间
*
* @param time1
* @param time2
* @return
*/
public static boolean checkTime(String time1, String time2) {
Calendar calendar = Calendar.getInstance();
Date date1 = calendar.getTime();
Date date11 = DateUtil.str2Date(DateUtil.date2Str(date1, "yyyy-MM-dd") + " " + time1);// 起始时间

Calendar c = Calendar.getInstance();
c.add(Calendar.DATE, 1);
Date date2 = c.getTime();
Date date22 = DateUtil.str2Date(DateUtil.date2Str(date2, "yyyy-MM-dd") + " " + time2);// 终止时间

Calendar scalendar = Calendar.getInstance();
scalendar.setTime(date11);// 起始时间

Calendar ecalendar = Calendar.getInstance();
ecalendar.setTime(date22);// 终止时间

Calendar calendarnow = Calendar.getInstance();

if (calendarnow.after(scalendar) && calendarnow.before(ecalendar)) {
return true;
} else {
return false;
}

}

/**
* haoxw 比较时间是否在这两个时间点之间
*
* @param date11
* @param date22
* @return
*/
public static boolean checkTime(Date date11, Date date22) {



Calendar scalendar = Calendar.getInstance();
scalendar.setTime(date11);// 起始时间

Calendar ecalendar = Calendar.getInstance();
ecalendar.setTime(date22);// 终止时间

Calendar calendarnow = Calendar.getInstance();

if (calendarnow.after(scalendar) && calendarnow.before(ecalendar)) {
return true;
} else {
return false;
}

}


public static boolean checkDate(String date1, String date2) {

Date date11 = DateUtil.str2Date(date1, "yyyy-MM-dd HH:mm:ss");// 起始时间

Date date22 = DateUtil.str2Date(date2, "yyyy-MM-dd HH:mm:ss");// 终止时间

Calendar scalendar = Calendar.getInstance();
scalendar.setTime(date11);// 起始时间

Calendar ecalendar = Calendar.getInstance();
ecalendar.setTime(date22);// 终止时间

Calendar calendarnow = Calendar.getInstance();

System.out.println(date11.toString());
System.out.println(date22.toString());
System.out.println(scalendar.toString());
System.out.println(ecalendar.toString());
System.out.println(calendarnow.toString());

if (calendarnow.after(scalendar) && calendarnow.before(ecalendar)) {
return true;
} else {
return false;
}
}

/**
* 获取interval天之前的日期
*
* @param interval
* @param starttime
* @param pattern
* @return
*/
public static Date getIntervalDate(String interval, Date starttime, String pattern) {
Calendar temp = Calendar.getInstance();
temp.setTime(starttime);
temp.add(temp.DATE, Integer.parseInt(interval));
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
String shijian = sdf.format(temp.getTime());
return str2Date(shijian);
}
   
public static Date formatDate(Date date){
SimpleDateFormat bartDateFormat =
new SimpleDateFormat("yyyy-MM-dd");
System.out.println(bartDateFormat.format(date));
SimpleDateFormat bartDateFormat1 =new SimpleDateFormat("yyyy-MM-dd");
try {
Date date1 = bartDateFormat1.parse(bartDateFormat.format(date));
} catch (ParseException e) {
e.printStackTrace();
}
System.out.println(date.getTime());
return date;

}

public static void main(String arf[]) {

/*String time1 = "2009-05-07 19:20:00";
String time2 = "2009-05-08 19:30:00";

DateUtil d = new DateUtil();
System.out.println(d.checkDate(time1, time2));
System.out.println(d.date2Str(new Date()));*/

//System.out.println(d.getIntervalDate("-3", new Date(), DEFAULT_PATTERN));
Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
System.out.println(calendar.toString());
System.out.println(DateUtil.str2Date("20090731","yyyyMMdd"));

System.out.println(DateUtil.getBeforeDate(new Date(),2 ));
System.out.println(DateUtil.DatePattern(new Date()));

    SimpleDateFormat bartDateFormat =
new SimpleDateFormat("yyyy-MM-dd");
Date date = new Date();
System.out.println("date;"+bartDateFormat.format(date));
SimpleDateFormat bartDateFormat1 =new SimpleDateFormat("yyyy-MM-dd");
try {
Date date1 = bartDateFormat1.parse(bartDateFormat.format(date));
System.out.println("日期："+date1);
} catch (ParseException e) {
e.printStackTrace();
}

}
转自：http://lucien-zzy.iteye.com/blog/2009811