String2Date && Date2String
首先，感谢阅览，能够帮到你是我的荣幸，有不足的挺多指教。
在java中不支持String和Date直接转换，提供了一个转换中间类SimpleDateFormat（import java.text.SimpleDateFormat;），通过SimpleDateFormat提供的两个方法进行转换：
/**
* Formats a Date into a date/time string.
* @param date the time value to be formatted into a time string.
* @return the formatted time string.
*/
public final String format(Date date)
{
return format(date, new StringBuffer(),
DontCareFieldPosition.INSTANCE).toString();
}
/**
* Parses text from the beginning of the given string to produce a date.
* The method may not use the entire text of the given string.
* <p>
* See the {@link #parse(String, ParsePosition)} method for more information
* on date parsing.
*
* @param source A <code>String</code> whose beginning should be parsed.
* @return A <code>Date</code> parsed from the string.
* @exception ParseException if the beginning of the specified string
* cannot be parsed.
*/
public Date parse(String source) throws ParseException
{
ParsePosition pos = new ParsePosition(0);
Date result = parse(source, pos);
if (pos.index == 0)
throw new ParseException("Unparseable date: \"" + source + "\"" ,
pos.errorIndex);
return result;
}创建SimpleDateFormat对象，相关函数语法
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
/**
SimpleDateFormat函数语法：
G 年代标志符
y 年
M 月
d 日
h 时 在上午或下午 (1~12)
H 时 在一天中 (0~23)
m 分
s 秒
S 毫秒
E 星期
D 一年中的第几天
F 一月中第几个星期几
w 一年中第几个星期
W 一月中第几个星期
a 上午 / 下午 标记符
k 时 在一天中 (1~24)
K 时 在上午或下午 (0~11)
z 时区 常见标准的写法"yyyy-MM-dd HH:mm:ss",注意大小写，时间是24小时制，24小时制转换成12小时制只需将HH改成hh,不需要另外的函数。
*/一般时间字符串格式：
/**
* 字符串转换为java.util.Date<br>
* 支持格式为 yyyy.MM.dd G 'at' hh:mm:ss z 如 '2022-1-1 AD at 22:10:59 PSD'<br>
* yy/MM/dd HH:mm:ss 如 '2022/1/1 17:55:00'<br>
* yy/MM/dd HH:mm:ss pm 如 '2022/1/1 17:55:00 pm'<br>
* yy-MM-dd HH:mm:ss 如 '2022-1-1 17:55:00' <br>
* yy-MM-dd HH:mm:ss am 如 '2022-1-1 17:55:00 am' <br>
*/
项目中使用的相对校多，具体转换实例如下：
import org.apache.commons.collections4.CollectionUtils;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.time.*;
import java.util.*;
/**
* @author: feng
* @date: 2018/3/16
* @description:
*/
public class DateUtils{
private static final int DAY_MILLISECONDS = 1000 * 24 * 60 * 60;
private static final int HOUR_MILLISECONDS = 1000 * 60 * 60;
private static final int MINUTE_MILLISECONDS = 1000 * 60;
//计算时间差，精确到天
public static int diffDays(Date start, Date end) {
long diff = end.getTime() - start.getTime();
return (int) (diff / (DAY_MILLISECONDS));
}
//计算时间差，精确到小时
public static int diffHours(Date start, Date end) {
long diff = end.getTime() - start.getTime();
return (int) (diff / (HOUR_MILLISECONDS));
}
//计算时间差，精确分钟
public static int diffMinutes(Date start, Date end) {
long diff = end.getTime() - start.getTime();
return (int) (diff / (MINUTE_MILLISECONDS));
}
//计算时间差，精确到分钟
public static int diffSeconds(Date start, Date end) {
long diff = end.getTime() - start.getTime();
return (int) (diff / 1000);
}
//获取当前时间，年-月-日
public static Date getToday() {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String s = sdf.format(new Date());
Date date = null;
try {
date = sdf.parse(s);
} catch (ParseException e) {
}
return date;
}
/**
* 获取前几天的时间
*
* @param date currentDate
* @param days beforeDate
* @return
*/
public static Date getDateBefore(Date date, int days) {
Calendar now = Calendar.getInstance();
now.setTime(date);
now.set(Calendar.DATE, now.get(Calendar.DATE) - days);
return now.getTime();
}
/**
* 获取后几天的时间
*
* @param date currentDate
* @param days afterDays
* @return
*/
public static Date getDateAfter(Date date, int days) {
Calendar now = Calendar.getInstance();
now.setTime(date);
now.set(Calendar.DATE, now.get(Calendar.DATE) + days);
return now.getTime();
}
//转换Date to String
public static String date2String(Date date,String str){
SimpleDateFormat sdf = new SimpleDateFormat(str);
return sdf.format(date);
}
public static Date parseDate(String str) {
return parseDate(str, "yyyy-MM-dd");
}
//转换String to Date,入参str:转换字符串，例如2018-01-01 00:00:00 pattern:转换后格式
public static Date parseDate(String str, String pattern) {
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern);
Date date = null;
try {
date = simpleDateFormat.parse(str);
} catch (ParseException e) {
e.printStackTrace();
}
return date;
}
public static List<Date> getDatesBetween(Date startDate, Date endDate) {
Long mils = (endDate.getTime() - startDate.getTime()) / (DAY_MILLISECONDS);
int days = mils.intValue();
List<Date> res = new ArrayList<>();
for (int i = 0; i < days; i++) {
res.add(org.apache.commons.lang3.time.DateUtils.addDays(startDate, i));
}
return res;
}
public static List<Date> getDatesBetweenIncludeEnd(Date startDate, Date endDate){
List<Date> res = getDatesBetween(startDate, endDate);
res.add(endDate);
return res;
}
public static Set<DayOfWeek> getWeekendDay(List<Integer> list) {
Set<DayOfWeek> res = new HashSet<>();
if (CollectionUtils.isEmpty(list)) {
return res;
}
for (Integer i : list) {
switch (i) {
case 1:
res.add(DayOfWeek.MONDAY);
break;
case 2:
res.add(DayOfWeek.TUESDAY);
break;
case 3:
res.add(DayOfWeek.WEDNESDAY);
break;
case 4:
res.add(DayOfWeek.THURSDAY);
break;
case 5:
res.add(DayOfWeek.FRIDAY);
break;
case 6:
res.add(DayOfWeek.SATURDAY);
break;
case 7:
res.add(DayOfWeek.SUNDAY);
break;
default:
}
}
return res;
}
public static DayOfWeek getDayOfWeek(Date date) {
Instant instant = date.toInstant();
ZoneId zoneId = ZoneId.systemDefault();
LocalDate localDate = LocalDateTime.ofInstant(instant, zoneId).toLocalDate();
return localDate.getDayOfWeek();
}
/**
* 将 1,2,3 .... 形式的星期集合 转化为 星期一,星期二,星期三 .... 这种形式
*
* @param weekDays
* @return
*/
public static List<String> weekDaysChange(List<String> weekDays) {
List<String> newWeekDays = new ArrayList<>();
for (String weekDay : weekDays) {
switch (weekDay) {
case "1":
newWeekDays.add("星期一");
break;
case "2":
newWeekDays.add("星期二");
break;
case "3":
newWeekDays.add("星期三");
break;
case "4":
newWeekDays.add("星期四");
break;
case "5":
newWeekDays.add("星期五");
break;
case "6":
newWeekDays.add("星期六");
break;
case "7":
newWeekDays.add("星期日");
break;
default:
}
}
return newWeekDays;
}
public static DayOfWeek getDayOfWeekFromNumber(Integer day) {
switch (day) {
case 1:
return DayOfWeek.MONDAY;
case 2:
return DayOfWeek.TUESDAY;
case 3:
return DayOfWeek.WEDNESDAY;
case 4:
return DayOfWeek.THURSDAY;
case 5:
return DayOfWeek.FRIDAY;
case 6:
return DayOfWeek.SATURDAY;
case 7:
return DayOfWeek.SUNDAY;
default:
}
return DayOfWeek.SUNDAY;
}
public static boolean isSameDay(Date date1, Date date2) {
return org.apache.commons.lang3.time.DateUtils.isSameDay(date1, date2);
}
public static Date addDays(Date date, int days){
return org.apache.commons.lang3.time.DateUtils.addDays(date, days);
}
public static int compareTime(Date date1, Date date2){
int t1;
int t2;
t1 = (int) (date1.getTime() % (24*60*60*1000L));
t2 = (int) (date2.getTime() % (24*60*60*1000L));
return (t1 - t2);
}
public static boolean isValidTonight(Date date1, Date date2){
Instant instant1 = date1.toInstant();
ZoneId zone = ZoneId.systemDefault();
LocalDateTime localDateTime1 = LocalDateTime.ofInstant(instant1, zone);
LocalTime localTime1 = localDateTime1.toLocalTime();
Instant instant2 = date2.toInstant();
LocalDateTime localDateTime2 = LocalDateTime.ofInstant(instant2, zone);
LocalTime localTime2 = localDateTime2.toLocalTime();
LocalTime now = LocalTime.now();
if(localTime1.isBefore(localTime2) && now.isBefore(localTime2)){
return true;
}else if(localTime1.isAfter(localTime2) && (now.isAfter(localTime1)||now.isBefore(localTime2))){
return true;
}
return false;
}
}