将字符串转换为对应日期
Date date = simpleDateFormat.parse(string);
将日期转换为字符串
String string = simpleDateFormat.format(date);
注意，因为可能定义的格式和实际字符串提供的格式不符合，所以会抛出异常。
将年月日的汉字日期转为 - - 分隔符的日期
public static void main(String[] args) throws ParseException {
//统一日期格式
String StrVal = "2018年05月22日";
Date d1 = new SimpleDateFormat("yyyy年MM月dd日").parse(StrVal);
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
String time = format.format(d1);
System.out.println(time);
}
/**
* 将日期对象格式化为指定格式的日期字符串
* @param date 传入的日期对象
* @param format 格式
* @return
*/
public static String formatDate(Date date,String format){
String result="";
SimpleDateFormat sdf=new SimpleDateFormat(format);
if(date!=null){
result=sdf.format(date);
}
return result;
}
/**
* 将日期字符串转换成一个日期对象
* @param dateStr 日期字符串
* @param format 格式
* @return
* @throws ParseException
*/
public static Date formatDate(String dateStr,String format) throws ParseException{
SimpleDateFormat sdf=new SimpleDateFormat(format);
return sdf.parse(dateStr);
}
public static void main(String[] args) throws ParseException {
Date date=new Date();
System.out.println(formatDate(date,"yyyy-MM-dd"));
System.out.println(formatDate(date,"yyyy-MM-dd HH:mm:ss"));
System.out.println(formatDate(date,"yyyy年MM月dd日HH时mm分ss秒"));
String dataStr="1989-11-02 18:01:41";
Date date2=formatDate(dataStr,"yyyy-MM-dd HH:mm:ss");
System.out.println(formatDate(date2,"yyyy-MM-dd HH:mm:ss"));
}运行输出：
2016-11-02
2016-11-02 18:06:50
2016年11月02日18时06分50秒
1989-11-02 18:01:41
SimpleDateFormat类主要是用作日期类型转换用的，常用的日期格式化
public static void main(String[] args) {
//默认输出格式
Date date=new Date();
System.out.println(date);
//日期格式化显示，首先定义格式
SimpleDateFormat sdf1=new SimpleDateFormat("yyyyMMdd");
SimpleDateFormat sdf2=new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat sdf3=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat sdf4=new SimpleDateFormat("yyyy年MM月dd日HH时mm分ss秒");
//将格式应用于日期
System.out.println(sdf1.format(date));
System.out.println(sdf2.format(date));
System.out.println(sdf3.format(date));
System.out.println(sdf4.format(date));
}
Calendar有个DAY_OF_WEEK 可以返回一个星期中的第几天；
这里说下注意点 老外的第一天是从星期日开始的，所以要-1；
import java.util.Calendar;
public class Test {
public static void main(String[] args) {
String[] weekDays = {"星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六"};
Calendar calendar=Calendar.getInstance();
System.out.println("今天是"+weekDays[calendar.get(Calendar.DAY_OF_WEEK)-1]);
}
}对日历进行操作
public static void main(String[] args) {
//默认输出格式
Date now = new Date();
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
String time = format.format(now);
System.out.println(time);
Calendar calendar = Calendar.getInstance();
calendar.setTime(now);
calendar.add(Calendar.MONTH, 1);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String nowTime = sdf.format(calendar.getTime());
System.out.println(nowTime);
calendar.add(Calendar.MONTH, -2);
String nowTime2 = sdf.format(calendar.getTime());
System.out.println(nowTime2);
}
获取时间
赋值时年月日时分秒常用的6个值，注意月份下标从0开始，所以取月份要+1
public static void main(String[] args) {
//默认输出格式
Date now = new Date();
SimpleDateFormat nowSdf = new SimpleDateFormat("yyyy-MM-dd");
System.out.println(nowSdf.format(now));
Calendar calendar = Calendar.getInstance();
// 赋值时年月日时分秒常用的6个值，注意月份下标从0开始，所以取月份要+1
System.out.println("年:" + calendar.get(Calendar.YEAR));
System.out.println("月:" + (calendar.get(Calendar.MONTH) + 1));
System.out.println("日:" + calendar.get(Calendar.DAY_OF_MONTH));
System.out.println("时:" + calendar.get(Calendar.HOUR_OF_DAY));
System.out.println("分:" + calendar.get(Calendar.MINUTE));
System.out.println("秒:" + calendar.get(Calendar.SECOND));
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String nowTime2 = sdf.format(calendar.getTime());
System.out.println(nowTime2);
}
设置时间
如果想设置为某个日期，可以一次设置年月日时分秒，由于月份下标从0开始赋值月份要-1
public static void main(String[] args) {
//默认输出格式
Date now = new Date();
SimpleDateFormat nowSdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
System.out.println(nowSdf.format(now));
Calendar calendar = Calendar.getInstance();
calendar.set(2013, 5, 4, 13, 44, 51);
calendar.set(Calendar.YEAR, 2014);//年
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String nowTime = sdf.format(calendar.getTime());
System.out.println(nowTime);
calendar.set(Calendar.MONTH, 7);//月（月份0代表1月）
SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String nowTime1 = sdf1.format(calendar.getTime());
System.out.println(nowTime1);
calendar.set(Calendar.DATE, 11);//日
calendar.set(Calendar.HOUR_OF_DAY, 15);//时
calendar.set(Calendar.MINUTE, 33);//分
calendar.set(Calendar.SECOND, 32);//秒
}
时间计算
public static void main(String[] args) {
//默认输出格式
Date now = new Date();
SimpleDateFormat nowSdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
System.out.println(nowSdf.format(now));
Calendar calendar = Calendar.getInstance();
calendar.setTime(now);
calendar.add(Calendar.YEAR, 1);//年
calendar.add(Calendar.MONTH, 1);//月
calendar.add(Calendar.DATE, 1);//日
//calendar.add(Calendar.DAY_OF_YEAR, 1);//今年的第 N 天
//calendar.add(Calendar.DAY_OF_MONTH, 1); // 本月第 N 天
//calendar.add(Calendar.DAY_OF_WEEK, 1);// 本周几
calendar.add(Calendar.HOUR_OF_DAY, -1);//时
calendar.add(Calendar.MINUTE, 1);//分
calendar.add(Calendar.SECOND, 1);//秒
//calendar.add(calendar.WEEK_OF_MONTH, 1);//增加一个礼拜
//calendar.add(calendar.WEEK_OF_YEAR,1);//增加一个礼拜
SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String nowTime1 = sdf1.format(calendar.getTime());
System.out.println(nowTime1);
}
日期的计算
获取本月最小天数与最大天数
public static void main(String[] args) {
//默认输出格式
Date now = new Date();
SimpleDateFormat nowSdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Calendar calendar = Calendar.getInstance();
int firstD = calendar.getActualMinimum(calendar.DAY_OF_MONTH);
int lastD = calendar.getActualMaximum(calendar.DAY_OF_MONTH);
System.out.println("获取本月的第一天和最后天：" + firstD +"," + lastD);
}
获取本周星期一、上周星期一、这周星期一
public static Date geLastWeekMonday(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(getThisWeekMonday(date));
cal.add(Calendar.DATE, -7);
return cal.getTime();
}
public static Date getThisWeekMonday(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
// 获得当前日期是一个星期的第几天
int dayWeek = cal.get(Calendar.DAY_OF_WEEK);
if (1 == dayWeek) {
cal.add(Calendar.DAY_OF_MONTH, -1);
}
// 设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一
cal.setFirstDayOfWeek(Calendar.MONDAY);
// 获得当前日期是一个星期的第几天
int day = cal.get(Calendar.DAY_OF_WEEK);
// 根据日历的规则，给当前日期减去星期几与一个星期第一天的差值
cal.add(Calendar.DATE, cal.getFirstDayOfWeek() - day);
return cal.getTime();
}
public static Date getNextWeekMonday(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(getThisWeekMonday(date));
cal.add(Calendar.DATE, 7);
return cal.getTime();
}
public static void main(String[] args) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
try {
Date date = sdf.parse("2017-09-10");
System.out.println("今天是" + sdf.format(date));
System.out.println("上周一" + sdf.format(geLastWeekMonday(date)));
System.out.println("本周一" + sdf.format(getThisWeekMonday(date)));
System.out.println("下周一" + sdf.format(getNextWeekMonday(date)));
} catch (Exception e) {
e.printStackTrace();
}
}
天数计算
用Date类计算日期差
public static void main(String[] args) {
Calendar love = Calendar.getInstance();
Calendar now = Calendar.getInstance();
love.set(2016, 8, 6); //真实的日期是2016-9-6;
int days = (int) ((now.getTimeInMillis() - love.getTimeInMillis()) / (24 * 60 * 60 * 1000.0));
System.out.println(days);
}
public static void main(String[] args) throws ParseException {
SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");//大小写还是很重要的
Date LoveDay=new Date();
Date now=new Date();
LoveDay=format.parse("2016-08-06");
int day=(int) ((now.getTime()-LoveDay.getTime())/(24*60*60*1000));
System.out.println(day);
}
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
public class DateUtils {
public static final String DATE_TIME_PATTERN = "yyyy-MM-dd HH:mm:ss";
public static final String MINUTE_PATTERN = "yyyy-MM-dd HH:mm";
public static final String HOUR_PATTERN = "yyyy-MM-dd HH:mm:ss";
public static final String DATE_PATTERN = "yyyy-MM-dd";
public static final String MONTH_PATTERN = "yyyy-MM";
public static final String YEAR_PATTERN = "yyyy";
public static final String MINUTE_ONLY_PATTERN = "mm";
public static final String HOUR_ONLY_PATTERN = "HH";
/**
* 日期相加减天数
* @param date 如果为Null，则为当前时间
* @param days 加减天数
* @param includeTime 是否包括时分秒,true表示包含
* @return
* @throws ParseException
*/
public static Date dateAdd(Date date, int days, boolean includeTime) throws ParseException{
if(date == null){
date = new Date();
}
if(!includeTime){
SimpleDateFormat sdf = new SimpleDateFormat(DateUtils.DATE_PATTERN);
date = sdf.parse(sdf.format(date));
}
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.DATE, days);
return cal.getTime();
}
/**
* 时间格式化成字符串
* @param date Date
* @param pattern StrUtils.DATE_TIME_PATTERN || StrUtils.DATE_PATTERN， 如果为空，则为yyyy-MM-dd
* @return
* @throws ParseException
*/
public static String dateFormat(Date date, String pattern) throws ParseException{
if(pattern==null||pattern.length()==0||pattern.equals(" ")){
pattern = DateUtils.DATE_PATTERN;
}
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
return sdf.format(date);
}
/**
* 字符串解析成时间对象
* @param dateTimeString String
* @param pattern StrUtils.DATE_TIME_PATTERN || StrUtils.DATE_PATTERN，如果为空，则为yyyy-MM-dd
* @return
* @throws ParseException
*/
public static Date dateParse(String dateTimeString, String pattern) throws ParseException{
if(pattern==null||pattern.length()==0||pattern.equals(" ")){
pattern = DateUtils.DATE_PATTERN;
}
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
return sdf.parse(dateTimeString);
}
/**
* 将日期时间格式成只有日期的字符串（可以直接使用dateFormat，Pattern为Null进行格式化）
* @param dateTime Date
* @return
* @throws ParseException
*/
public static String dateTimeToDateString(Date dateTime) throws ParseException{
String dateTimeString = DateUtils.dateFormat(dateTime, DateUtils.DATE_TIME_PATTERN);
return dateTimeString.substring(0, 10);
}
/**
* 当时、分、秒为00:00:00时，将日期时间格式成只有日期的字符串，
* 当时、分、秒不为00:00:00时，直接返回
* @param dateTime Date
* @return
* @throws ParseException
*/
public static String dateTimeToDateStringIfTimeEndZero(Date dateTime) throws ParseException{
String dateTimeString = DateUtils.dateFormat(dateTime, DateUtils.DATE_TIME_PATTERN);
if(dateTimeString.endsWith("00:00:00")){
return dateTimeString.substring(0, 10);
}else{
return dateTimeString;
}
}
/**
* 将日期时间格式成日期对象，和dateParse互用
* @param dateTime Date
* @return Date
* @throws ParseException
*/
public static Date dateTimeToDate(Date dateTime) throws ParseException{
Calendar cal = Calendar.getInstance();
cal.setTime(dateTime);
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
return cal.getTime();
}
/**
* 时间加减小时
* @param startDate 要处理的时间，Null则为当前时间
* @param hours 加减的小时
* @return Date
*/
public static Date dateAddHours(Date startDate, int hours) {
if (startDate == null) {
startDate = new Date();
}
Calendar c = Calendar.getInstance();
c.setTime(startDate);
c.set(Calendar.HOUR, c.get(Calendar.HOUR) + hours);
return c.getTime();
}
/**
* 时间加减分钟
* @param startDate 要处理的时间，Null则为当前时间
* @param minutes 加减的分钟
* @return
*/
public static Date dateAddMinutes(Date startDate, int minutes) {
if (startDate == null) {
startDate = new Date();
}
Calendar c = Calendar.getInstance();
c.setTime(startDate);
c.set(Calendar.MINUTE, c.get(Calendar.MINUTE) + minutes);
return c.getTime();
}
/**
* 时间加减秒数
* @param startDate 要处理的时间，Null则为当前时间
* @param minutes 加减的秒数
* @return
*/
public static Date dateAddSeconds(Date startDate, int seconds) {
if (startDate == null) {
startDate = new Date();
}
Calendar c = Calendar.getInstance();
c.setTime(startDate);
c.set(Calendar.SECOND, c.get(Calendar.SECOND) + seconds);
return c.getTime();
}
/**
* 时间加减天数
* @param startDate 要处理的时间，Null则为当前时间
* @param days 加减的天数
* @return Date
*/
public static Date dateAddDays(Date startDate, int days) {
if (startDate == null) {
startDate = new Date();
}
Calendar c = Calendar.getInstance();
c.setTime(startDate);
c.set(Calendar.DATE, c.get(Calendar.DATE) + days);
return c.getTime();
}
/**
* 时间加减月数
* @param startDate 要处理的时间，Null则为当前时间
* @param months 加减的月数
* @return Date
*/
public static Date dateAddMonths(Date startDate, int months) {
if (startDate == null) {
startDate = new Date();
}
Calendar c = Calendar.getInstance();
c.setTime(startDate);
c.set(Calendar.MONTH, c.get(Calendar.MONTH) + months);
return c.getTime();
}
/**
* 时间加减年数
* @param startDate 要处理的时间，Null则为当前时间
* @param years 加减的年数
* @return Date
*/
public static Date dateAddYears(Date startDate, int years) {
if (startDate == null) {
startDate = new Date();
}
Calendar c = Calendar.getInstance();
c.setTime(startDate);
c.set(Calendar.YEAR, c.get(Calendar.YEAR) + years);
return c.getTime();
}
/**
* 时间比较（如果myDate>compareDate返回1，<返回-1，相等返回0）
* @param myDate 时间
* @param compareDate 要比较的时间
* @return int
*/
public static int dateCompare(Date myDate, Date compareDate) {
Calendar myCal = Calendar.getInstance();
Calendar compareCal = Calendar.getInstance();
myCal.setTime(myDate);
compareCal.setTime(compareDate);
return myCal.compareTo(compareCal);
}
/**
* 获取两个时间中最小的一个时间
* @param date
* @param compareDate
* @return
*/
public static Date dateMin(Date date, Date compareDate) {
if(date == null){
return compareDate;
}
if(compareDate == null){
return date;
}
if(1 == dateCompare(date, compareDate)){
return compareDate;
}else if(-1 == dateCompare(date, compareDate)){
return date;
}
return date;
}
/**
* 获取两个时间中最大的一个时间
* @param date
* @param compareDate
* @return
*/
public static Date dateMax(Date date, Date compareDate) {
if(date == null){
return compareDate;
}
if(compareDate == null){
return date;
}
if(1 == dateCompare(date, compareDate)){
return date;
}else if(-1 == dateCompare(date, compareDate)){
return compareDate;
}
return date;
}
/**
* 获取两个日期（不含时分秒）相差的天数，不包含今天
* @param startDate
* @param endDate
* @return
* @throws ParseException
*/
public static int dateBetween(Date startDate, Date endDate) throws ParseException {
Date dateStart = dateParse(dateFormat(startDate, DATE_PATTERN), DATE_PATTERN);
Date dateEnd = dateParse(dateFormat(endDate, DATE_PATTERN), DATE_PATTERN);
return (int) ((dateEnd.getTime() - dateStart.getTime())/1000/60/60/24);
}
/**
* 获取两个日期（不含时分秒）相差的天数，包含今天
* @param startDate
* @param endDate
* @return
* @throws ParseException
*/
public static int dateBetweenIncludeToday(Date startDate, Date endDate) throws ParseException {
return dateBetween(startDate, endDate) + 1;
}
/**
* 获取日期时间的年份，如2017-02-13，返回2017
* @param date
* @return
*/
public static int getYear(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
return cal.get(Calendar.YEAR);
}
/**
* 获取日期时间的月份，如2017年2月13日，返回2
* @param date
* @return
*/
public static int getMonth(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
return cal.get(Calendar.MONTH) + 1;
}
/**
* 获取日期时间的第几天（即返回日期的dd），如2017-02-13，返回13
* @param date
* @return
*/
public static int getDate(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
return cal.get(Calendar.DATE);
}
/**
* 获取日期时间当月的总天数，如2017-02-13，返回28
* @param date
* @return
*/
public static int getDaysOfMonth(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
return cal.getActualMaximum(Calendar.DATE);
}
/**
* 获取日期时间当年的总天数，如2017-02-13，返回2017年的总天数
* @param date
* @return
*/
public static int getDaysOfYear(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
return cal.getActualMaximum(Calendar.DAY_OF_YEAR);
}
/**
* 根据时间获取当月最大的日期
* <li>2017-02-13，返回2017-02-28</li>
* <li>2016-02-13，返回2016-02-29</li>
* <li>2016-01-11，返回2016-01-31</li>
* @param date Date
* @return
* @throws Exception
*/
public static Date maxDateOfMonth(Date date) throws Exception {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
int value = cal.getActualMaximum(Calendar.DATE);
return dateParse(dateFormat(date, MONTH_PATTERN) + "-" + value, null);
}
/**
* 根据时间获取当月最小的日期，也就是返回当月的1号日期对象
* @param date Date
* @return
* @throws Exception
*/
public static Date minDateOfMonth(Date date) throws Exception {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
int value = cal.getActualMinimum(Calendar.DATE);
return dateParse(dateFormat(date, MONTH_PATTERN) + "-" + value, null);
}
} public static void main(String[] args) throws Exception {
System.out.println(dateTimeToDate(new Date()));
System.out.println(dateParse("2017-02-04 14:58:20", null));
System.out.println(dateTimeToDateStringIfTimeEndZero(new Date()));
System.out.println(dateTimeToDateStringIfTimeEndZero(dateTimeToDate(new Date())));
System.out.println(dateBetween(dateParse("2017-01-30", null), dateParse("2017-02-01", null)));
System.out.println(dateBetweenIncludeToday(dateParse("2017-01-30", null), dateParse("2017-02-01", null)));
System.out.println(getDate(dateParse("2017-01-17", null)));
System.out.println(getDaysOfMonth(dateParse("2017-02-01", null)));
System.out.println(getDaysOfYear(dateParse("2017-01-30", null)));
/* System.out.println(dateFormat(dateAddMonths(dateParse("2017-02-07", StrUtils.MONTH_PATTERN), -12), StrUtils.MONTH_PATTERN));*/
System.out.println(dateFormat(maxDateOfMonth(dateParse("2016-02", "yyyy-MM")), null));
System.out.println(dateFormat(minDateOfMonth(dateParse("2016-03-31", null)), null));
}
