java常用日期函数总结

请记得要引入java.util.Date和java.text.SimpleDateFormat两个包 

1.计算某一月份的最大天数 

Calendar time=Calendar.getInstance(); 
time.clear(); 
time.set(Calendar.YEAR,year); 
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，最好先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 
Date date=new Date(); 
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss"); 

System.out.println(df.format(date)); 

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, 9); 
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"); 
Calendar 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 
(1)add()方法 
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd"); 
Calendar cal=Calendar.getInstance(); 
cal.set(Calendar.YEAR, 2006); 
cal.set(Calendar.MONTH, 9); 
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 
2006-10-03 
(2)roll方法 
cal.set(Calendar.YEAR, 2006); 
cal.set(Calendar.MONTH, 9); 
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： 
2006-10-29 
2006-10-03 

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 
(1)传进Calendar对象 
/** *//**计算两个时间之间相隔天数 
* @param startday 开始时间 
* @param endday 结束时间 
* @return 
*/ 
public int getIntervalDays(Calendar startday,Calendar endday)...{ 
//确保startday在endday之前 
if(startday.after(endday))...{ 
Calendar cal=startday; 
startday=endday; 
endday=cal; 
} 
//分别得到两个时间的毫秒数 
long sl=startday.getTimeInMillis(); 
long el=endday.getTimeInMillis(); 

long ei=el-sl; 
//根据毫秒数计算间隔天数 
return (int)(ei/(1000*60*60*24)); 
} 
(2)传进Date对象 
/** *//**计算两个时间之间相隔天数 
* @param startday 开始时间 
* @param endday 结束时间 
* @return 
*/ 
public int getIntervalDays(Date startday,Date endday)...{ 
//确保startday在endday之前 
if(startday.after(endday))...{ 
Date cal=startday; 
startday=endday; 
endday=cal; 
} 
//分别得到两个时间的毫秒数 
long sl=startday.getTime(); 
long el=endday.getTime(); 

long ei=el-sl; 
//根据毫秒数计算间隔天数 
return (int)(ei/(1000*60*60*24)); 
}同理，可以用相同的方法计算出任意两个时间相隔的小时数，分钟数，秒钟数等 
注：以上方法是完全按时间计算，有时并不能令人满意，如： 
startday="2006-10-11 20:00:00" 
endday="2006-10-12 8:00:00" 
计算结果为0，但是我们也许相让计算结果变为1，此时可以用如下方法实现： 
在传参之前，先设定endday的时间，如： 
endday.set(Calendar.HOUR_OF_DAY, 23); 
endday.set(Calendar.MINUTE, 59); 
endday.set(Calendar.SECOND, 59); 
endday.set(Calendar.MILLISECOND, 59); 
这样再传进去startday,endday，则结果就如我们所愿了。不过，如果嫌以上方法麻烦，可以参考以下方法： 
(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)) ...{ // swap dates so that d1 is start and d2 is end 
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; 
} 


获取系统当前时间： 
public static String getSystemTime(){ 
Date date=new Date(); 
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 
return df.format(date); 
} 

//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） 

java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat("M/dd/yyyy hh:mm:ss a",java.util.Locale.US); 

java.util.Date d = sdf.parse("5/13/2003 10:31:37 AM"); 


SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 

String mDateTime1=formatter.format(d); 


   //当前时间 

   Calendar cal = Calendar.getInstance(); 

// SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 

SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss G E D F w W a E F"); 

   String mDateTime=formatter.format(cal.getTime()); 



   //1年前日期 

   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); 

   

   //明天日期 

   myDate=new java.util.Date(); 

   myTime=(myDate.getTime()/1000)+60*60*24; 

   myDate.setTime(myTime*1000); 

   mDate=formatter.format(myDate); 



//两个时间之间的天数 

   SimpleDateFormat myFormatter = new SimpleDateFormat("yyyy-MM-dd"); 

   java.util.Date date= myFormatter.parse("2003-05-1"); 

   java.util.Date mydate= myFormatter.parse("1899-12-30"); 

   long day=(date.getTime()-mydate.getTime())/(24*60*60*1000); 





//加半小时 

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss"); 

java.util.Date date1 = format.parse("2002-02-28 23:16:00"); 

long Time=(date1.getTime()/1000)+60*30; 

date1.setTime(Time*1000); 

String mydate1=formatter.format(date1); 







//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); 

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 

package personal.jessica; 
import java.util.Date; 
import java.util.Calendar; 
import java.sql.Timestamp; 
import java.text.DateFormat; 
import java.text.SimpleDateFormat; 
import java.util.Locale; 
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 java.lang.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(); 
} 
} 
} 

下面是例子： 

package test;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;

import java.util.Calendar;
import java.util.Date;
import java.util.Hashtable;

import javax.swing.JOptionPane;



public class Test2{

    public static boolean isdate(String s){
        String a[]=s.split("-");
        boolean flg=true;
        if(!(Integer.parseInt(a[0])>=1950 && Integer.parseInt(a[0])<=2050)){
                flg=false;
        }
        return flg;
    }

    public static boolean checkDate(String s){
        boolean ret = true;
        try{
            DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
            ret = df.format(df.parse(s)).equals(s);
        }
        catch(ParseException e){
            ret = false;
        }
        return ret;
    }

    public Object dateinfo(String s){
        String a[]=s.split("-",2);
        Hashtable fest =new Hashtable();
        fest.put("01-01","元旦节");
        fest.put("02-14","情人节");
        fest.put("03-12","植树节");
        fest.put("03-15","消费者节");
        fest.put("04-01","愚人节");
        fest.put("04-05","清明节");
        fest.put("05-01","劳动节");
        fest.put("06-01","儿童节");
        fest.put("07-01","建党节");
        fest.put("08-01","建军节");
        fest.put("09-10","教师节");
        fest.put("10-01","国庆节");
        fest.put("12-25","圣诞节");
        if(fest.containsKey(a[1])){
        return fest.get(a[1]);
        }
        else{
        return "无节日";
        }
    }

    public String xingzuo(Date s){
        Calendar cal = Calendar.getInstance();
        cal.setTime(s);
        String xingzuo="无";
        int day=cal.get(Calendar.DAY_OF_YEAR);
        if((cal.get(Calendar.YEAR)%4==0)&&(cal.get(Calendar.YEAR)%100!=0)||(cal.get(Calendar.YEAR)%400==0)){
            if((day>=1 &&day<=19)||(day>=357&&day<=366)){
                xingzuo= "魔蝎座";
            }
            else if(day>=20 &&day<=49){
                xingzuo= "水瓶座";
            }
            else if(day>=50 &&day<=80){
                xingzuo= "双鱼座";
            }
            else if(day>=81 &&day<=110){
                xingzuo= "白羊座";
            }
            else if(day>=111 &&day<=141){
                xingzuo= "金牛座";
            }
            else if(day>=142 &&day<=173){
                xingzuo= "双子座";
            }
            else if(day>=174 &&day<=203){
                xingzuo= "巨蟹座";
            }
            else if(day>=204 &&day<=235){
                xingzuo= "狮子座";
            }
            else if(day>=236 &&day<=266){
                xingzuo= "处女座";
            }
            else if(day>=267 &&day<=296){
                xingzuo= "天秤座";
            }
            else if(day>=297 &&day<=326){
                xingzuo= "天蝎座";
            }
            else if(day>=327 &&day<=356){
                xingzuo= "射手座";
            }
        }
        else{
            if((day>=1 &&day<=19)||(day>=357&&day<=366)){
                xingzuo= "魔蝎座";
            }
            else if(day>=20 &&day<=48){
                xingzuo= "水瓶座";
            }
            else if(day>=49 &&day<=79){
                xingzuo= "双鱼座";
            }
            else if(day>=80 &&day<=109){
                xingzuo= "白羊座";
            }
            else if(day>=110 &&day<=140){
                xingzuo= "金牛座";
            }
            else if(day>=141 &&day<=172){
                xingzuo= "双子座";
            }
            else if(day>=173 &&day<=202){
                xingzuo= "巨蟹座";
            }
            else if(day>=203 &&day<=234){
                xingzuo= "狮子座";
            }
            else if(day>=235 &&day<=265){
                xingzuo= "处女座";
            }
            else if(day>=266 &&day<=295){
                xingzuo= "天秤座";
            }
            else if(day>=296 &&day<=325){
                xingzuo= "天蝎座";
            }
            else if(day>=326 &&day<=355){
                xingzuo= "射手座";
            }
        }
        return xingzuo;
    }

    public Date parseDate(String s){
        SimpleDateFormat bartDateFormat = new SimpleDateFormat("yyyy-MM-dd");
            try {
                Date date3 = bartDateFormat.parse(s);
                date3=bartDateFormat.parse(s);
                return date3;
            }
            catch (Exception ex) {
                return null;
            }
    }

    public static void main(String[] args) {
        Calendar cal = Calendar.getInstance();
        Test2 test2=new Test2();
        String date1=JOptionPane.showInputDialog("请你输入日期，格式如2000-10-15");

        while(!(Test2.checkDate(date1)&&Test2.isdate(date1))){
            date1=JOptionPane.showInputDialog("请你输入日期，格式如2000-10-15");
        }
            SimpleDateFormat bartDateFormat1 = new SimpleDateFormat("yyyy,MM,dd,EEEE");
            SimpleDateFormat bartDateFormat2 = new SimpleDateFormat("yyyy-MM-dd");
            Date date2=test2.parseDate(date1);
            String festinfo=(String)test2.dateinfo(date1);
            System.out.println(bartDateFormat1.format(date2) +","+ festinfo+","+ test2.xingzuo(date2));



            String day=JOptionPane.showInputDialog("请你输入要查询N天后的日期信息");
            cal.setTime(date2);
            cal.add(Calendar.DATE, Integer.parseInt(day));
            String date5=bartDateFormat2.format(cal.getTime());
            festinfo=(String)test2.dateinfo(date5);
            System.out.println(bartDateFormat1.format(cal.getTime())+","+ festinfo+","+ test2.xingzuo(cal.getTime()));
    }
}