java日期处理
单独获取当前的年，月，日，时，分，秒
Calendar cal=Calendar.getInstance();
cal.setTime(new java.util.Date());
int year=cal.get(Calendar.YEAR);
int month=cal.get(Calendar.MONTH)+1;
int date=cal.get(Calendar.DATE);
int hour=cal.get(Calendar.HOUR);
int minute=cal.get(Calendar.MINUTE);
int second=cal.get(Calendar.SECOND);
int milliSecond=cal.get(https://www.360docs.net/doc/7118498837.html,LISECOND);
1.基本的获取时间方法
public class TestDate {
public static void main(String args[]) {
java.util.Date utildate=new java.util.Date();
System.out.println(utildate);
}
}
输出结果如下：
Mon Mar 12 17:40:00 CST 2007
2.获取年月日格式的时间
public class TestDate {
public static void main(String args[]) {
java.util.Date utildate=new java.util.Date();
java.sql.Date date=new java.sql.Date(utildate.getTime());
System.out.println(date);
}
}
输出结果如下：
2007-03-12
3.获取时分秒格式的时间
import java.util.*;
import java.text.*;
public class TestDate {
public static void main(String args[]) {
java.util.Date utildate=new java.util.Date();
String str=DateFormat.getTimeInstance().format(utildate);
System.out.println(str);
}
}
输出结果如下：
17:41:21
4.获取时间戳
import java.util.*;
public class TestDate {
public static void main(String args[]) {
java.util.Date utildate=new java.util.Date();
System.out.println(utildate.getTime());
}
}
或者用下面的方法:
public class TestDate {
public static void main(String args[]) {
long time=System.currentTimeMillis();
System.out.println(time);
}
}
输出结果如下：
1173692497326
5.按指定格式获取时间
import java.util.*;
import java.text.*;
public class TestDate {
public static void main(String args[]) {
Date today=new Date();
SimpleDateFormat f=new SimpleDateFormat("yyyy年MM月dd日
hh:mm:ss");
String time=f.format(today);
System.out.println(time);
}
}
格式里的时如果用hh表示用12小时制，HH表示用24小时制。MM必须是大写!
输出结果如下：
2007年03月12日05:42:08
JS获取当前年月的方法：
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package com.snail.gequ.action;
import java.util.Calendar;
import java.util.Date;
import org.apache.log4j.Logger;
import org.hibernate.criterion.Expression;
import org.hibernate.criterion.Projections;
import https://www.360docs.net/doc/7118498837.html,mons.basedao.IBaseDAO;
import https://www.360docs.net/doc/7118498837.html,ponent.beans.Gequ;
import https://www.360docs.net/doc/7118498837.html,ponent.beans.Gequzhuanji;
import https://www.360docs.net/doc/7118498837.html,ponent.beans.Hu
iyuan;
import https://www.360docs.net/doc/7118498837.html,ponent.beans.Renqirecord;
public class RenQiRecordUtil {
private static final long serialVersionUID = 3193922028309094171L;
private final static Logger logger = Logger
.getLogger(RenQiRecordUtil.class);
protected Integer getMonthOfThisYear() {
Calendar cal = Calendar.getInstance();
cal.setTime(new Date());
return cal.get(Calendar.MONTH) + 1;
}
protected Date getTimeByMonth(Integer month) {
Calendar cal = Calendar.getInstance();
cal.setTime(new Date());
cal.set(Calendar.MONTH, month - 1);
return cal.getTime();
}
protected Date getMonthBegin(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set(cal.get(Calendar.YEAR), cal.get(Calendar.MONTH), 1, 0, 0, 0);
return cal.getTime();
}
protected Date getMonthEnd(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal
.set(cal.get(Calendar.YEAR), cal.get(Calendar.MONTH) + 1, 1, 0,
0, 0);
cal.set(Calendar.SECOND, cal.get(Calendar.SECOND) - 1);
return cal.getTime();
}
protected Date getWeekBegin(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
Date mm=nDaysAgo(cal.get(Calendar.DAY_OF_WEEK)-2,date);
return getDayBegin(mm);
}
protected Date getWeekEnd(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
Date mm=nDaysAfter(cal.get(8-Calendar.DAY_OF_WEEK),date);
return getDayEnd(mm);
}
protected Date nDaysAfter(int n,Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set(Calendar.DAY_OF_MONTH, cal.get(Calendar.DAY_OF_MONTH)+n);
return cal.getTime();
}
protected Date getDayBegin(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set(cal.get(Calendar.YEAR), cal.get(Calendar.MONTH), cal.get(Calendar.DAY_OF_MONTH), 0, 0, 0);
return cal.getTime();
}
protected Date getDayEnd(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal
.set(cal.get(Calendar.YEAR), cal.get(Calendar.MONTH),cal.get(Calendar.DAY_OF_MONTH)+1, 0,
0, 0);
cal.set(Calendar.SECOND, cal.get(Calendar.SECOND) - 1);
return cal.getTime();
}
protected Date nMonthsAgo(Integer n,Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set
(Calendar.MONTH, cal.get(Calendar.MONTH) - n);
return cal.getTime();
}
protected Date nDaysAgo(Integer n,Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set(Calendar.DAY_OF_MONTH, cal.get(Calendar.DAY_OF_MONTH) -n);
return cal.getTime();
}
public RenQiRecordUtil() {
// TODO Auto-generated constructor stub
}
}
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
package com.hefeng.test;
import java.text.DateFormat;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
public class TimeTest {
//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
/**
* @param args
*/
public static void main(String[] args) {
TimeTest tt = new TimeTest();
System.out.println("获取当天日期:"+tt.getNowTime("yyyy-MM-dd"));
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("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.getTh
isSeasonTime(11));
System.out.println("获取两个日期之间间隔天数2008-12-1~2008-9.29:"+TimeTest.getTwoDay("2008-12-1","2008-9-29"));
}
/**
* 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 = TimeTest.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;
}
//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);
}
}
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
1.计算某一月份的最大天数
Calendar time=Calendar.getInstance();
time.clear();
time.set(Calendar.YEAR,year); //year 为 int
time.set(Calendar.MONTH,i-1);//注意,Calendar对象默认一月为0
int day=time.getActualMaximum(Calendar.DAY_OF_MONTH);//本月份的天数
注：在使用set方法之前，必须先clear一下，否则很多信息会继承自系统当前时间
2.Calendar和Date的转化
(1) Calendar转化为Date
Calendar cal=Calendar.getInstance();
Date date=cal.getTime();
(2) Date转化为Calendar
Date date=new Date();
Calendar cal=Calendar.getInstance();
cal.setTime(date);
3.格式化输出日期时间 （这个用的比较多）
Date date=new Date();
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
String time=df.format(date);
System.out.println(time);
4.计算一年中的第几星期
(1)计算某一天是一年中的第几星期
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH,;
cal.set(Calendar.DAY_OF_MONTH, 3);
int weekno=cal.get(Calendar.WEEK_OF_YEAR);
(2)计算一年中的第几星期是几号
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");
Cale
ndar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.WEEK_OF_YEAR, 1);
cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println(df.format(cal.getTime()));
输出:
2006-01-02
5.add()和roll()的用法(不太常用)
(1)add()方法
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH,;
cal.set(Calendar.DAY_OF_MONTH, 3);
cal.add(Calendar.DATE, -4);
Date date=cal.getTime();
System.out.println(df.format(date));
cal.add(Calendar.DATE, 4);
date=cal.getTime();
System.out.println(df.format(date));
输出：
2006-08-30
2006-09-03
(2)roll方法
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH,;
cal.set(Calendar.DAY_OF_MONTH, 3);
cal.roll(Calendar.DATE, -4);
date=cal.getTime();
System.out.println(df.format(date));
cal.roll(Calendar.DATE, 4);
date=cal.getTime();
System.out.println(df.format(date));
输出：
2006-09-29
2006-09-03
可见，roll()方法在本月内循环，一般使用add()方法；
6.计算两个任意时间中间的间隔天数（这个比较常用）
(1)传进Calendar对象
public int getIntervalDays(Calendar startday,Calendar endday)...{
if(startday.after(endday))...{
Calendar cal=startday;
startday=endday;
endday=cal;
}
long sl=startday.getTimeInMillis();
long el=endday.getTimeInMillis();
long ei=el-sl;
return (int)(ei/(1000*60*60*24));
}
(2)传进Date对象
public int getIntervalDays(Date startday,Date endday)...{
if(startday.after(endday))...{
Date cal=startday;
startday=endday;
endday=cal;
}
long sl=startday.getTime();
long el=endday.getTime();
long ei=el-sl;
return (int)(ei/(1000*60*60*24));
}
(3)改进精确计算相隔天数的方法
public int getDaysBetween (Calendar d1, Calendar d2) ...{
if (d1.after(d2)) ...{
java.util.Calendar swap = d1;
d1 = d2;
d2 = swap;
}
int days = d2.get(Calendar.DAY_OF_YEAR) - d1.get(Calendar.DAY_OF_YEAR);
int y2 = d2.get(Calendar.YEAR);
if (d1.get(Calendar.YEAR) != y2) ...{
d1 = (Calendar) d1.clone();
do ...{
days += d1.getActualMaximum(Calendar.DAY_OF_YEAR);//得到当年的实际天数
d1.add(Calendar.YEAR, 1);
} while (d1.get(Calendar.YEAR) != y2);
}
return days;
}
注意：通过上面的方法可以衍生出求任何时间，如要查出邮箱三周之内收到的邮件（得到当前系统时间－再得到三周前时间）用收件的时间去匹配 最好装化成 long去比较
如：1年前日期（注意毫秒的转换）
java.util.Date myDate=new java.util.Date();
long myTime=(myDate.getTime()/1000)-60*60*24*365;
myDate.setTime(myTime*1000);
String mDate=formatter.format(myDate);
7. String 和 Date ，Long 之间相互转换 （最常用）
字符串转化成时间类型（字符串可以是任意类型，只要和SimpleDateFormat中的格式一致即可）
通常我们取时间跨度的时候，会substring出具体时间－－long－比较
java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat("M/dd/yyyy hh:mm:ss a",https://www.360docs.net/doc/7118498837.html,);
java.util.Date d = sdf.parse("5/13/2003 10:31:37 AM");
long dvalue=d.getTime();
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String mDateTime1=formatter.format(d);
8. 通过时间求时间
年月周求日期
SimpleDateFormat formatter2 = new SimpleDateFormat("yyyy-MM F E");
java.util.Date date2= formatter2.parse("2003-05 5 星期五");
SimpleDateFormat formatter3 = new SimpleDateFormat("yyyy-MM-dd");
String mydate2=formatter3.format(date2);
求是星期几
mydate= myFormatter.parse("2001-1-1");
SimpleDateFormat formatter4 = new SimpleDateFormat("E");
String mydate3=formatter4.format(mydate);
9. java 和 具体的数据库结合
在开发web应用中，针对不同的数据库日期类型，我们需要在我们的程序中对日期类型做各种不同的转换。若对应数据库数据是oracle的Date类型，即只需要年月日的，可以选择使用java.sql.Date类型，若对应的是MSsqlserver 数据库的DateTime类型，即需要年月日时分秒的，选择java.sql.Timestamp类型
你可以使用dateFormat定义时间日期的格式，转一个字符串即可
class Datetest{
*method 将字符串类型的日期转换为一个timestamp（时间戳记java.sql.Timestamp）
*@param dateString 需要转换为timestamp的字符串
*@return dataTime timestamp
public final static java.sql.Timestamp string2Time(String dateString)
throws java.text.ParseException {
DateFormat dateFormat;
dateFormat = new SimpleDateFormat("yyyy-MM-dd kk:mm:ss.SSS", Locale.ENGLISH);//设定格式
//dateFormat = new SimpleDateFormat("yyyy-MM-dd kk:mm:ss", Locale.ENGLISH);
dateFormat.setLenient(false);
java.util.Date timeDate = dateFormat.parse(dateString);//util类型
java.sql.Timestamp dateTime = new java.sql.Timestamp(timeDate.getTime());//Timestamp类型,timeDate.getTime()返回一个long型
return dateTime;
}
*method 将字符串类型的日期转换为一个Date（java.sql.Date）
*@param dateString 需要转换为Date的字符串
*@return dataTime Date
public final static java.sql.Date string2Date(String dateString)
throws https://www.360docs.net/doc/7118498837.html,ng.Exception {
DateFormat dateFormat;
dateFormat = new SimpleDateFormat("yyyy-MM-dd", Locale.ENGLISH);
dateFormat.setLenient(false);
java.util.Date timeDate = dateFormat.parse(dateString);//util类型
java.sql.Date dateTime = new java.sql.Date(timeDate.getTime());//sql类型
return dateTime;
}
public static void main(String[] args){
Date da = new Date();
注意：这个地方da.getTime()得到的是一个long型的值
System.out.println(da.getTime());
由日期date转换为timestamp
第一种方法：使用new Timestamp(long)
Timestamp t = new Timestamp(new Date().getTime());
System.out.println(t);
第二种方法：使用Timestamp(int year,int month,int date,int hour,int minute,int second,int nano)
Timestamp tt = new Timestamp(Calendar.getInstance().get(
Calendar.YEAR) - 1900, Calendar.getInstance().get(
Calendar.MONTH), Calendar.getInstance().get(
Calendar.DATE), Calendar.getInstance().get(
Calendar.HOUR), Calendar.getInstance().get(
Calendar.MINUTE), Calendar.getInstance().get(
Calendar.SECOND), 0);
System.out.println(tt);
try {
String sToDate = "2005-8-18";//用于转换成java.sql.Date的字符串
String sToTimestamp = "2005-8-18 14:21:12.123";//用于转换成java.sql.Timestamp的字符串
Date date1 = string2Date(sToDate);
Timestamp date2 = string2Time(sToTimestamp);
System.out.println("Date:"+date1.toString());//结果显示
System.out.println("Timestamp:"+date2.toString());//结果显示
}catch(Exception e) {
e.printStackTrace();
}
}
}