java日期类Date与DateFormat源码详解
Date类的定义
public class Date
implements java.io.Serializable, Cloneable, Comparable<Date>
{
private static final BaseCalendar gcal =
CalendarSystem.getGregorianCalendar();
private static BaseCalendar jcal;
private transient long fastTime;
private transient BaseCalendar.Date cdate;
// Initialized just before the value is used. See parse().
private static int defaultCenturyStart;
private static final long serialVersionUID = 7523967970034938905L;
public Date() {
this(System.currentTimeMillis());
}
public Date(long date) {
fastTime = date;
}
public Object clone() {
Date d = null;
try {
d = (Date)super.clone();
if (cdate != null) {
d.cdate = (BaseCalendar.Date) cdate.clone();
}
} catch (CloneNotSupportedException e) {} // Won't happen
return d;
}
}无参构造函数Date()内部会自动调用System.currentTimeMills()来获取该Date对象被创建时的时间戳（long类型，代表从1970年1月1日至现在所经历的毫秒数）。
Date(long date)需要调用者手动传入时间戳，来获得一个特定时间的Date对象。fastTime作为该类的成员变量保存对象的时间戳数据，以供Date类其他函数调用。
public long getTime() {
return getTimeImpl();
}
private final long getTimeImpl() {
if (cdate != null && !cdate.isNormalized()) {
normalize();
}
return fastTime;
}
public void setTime(long time) {
fastTime = time;
cdate = null;
}
public boolean before(Date when) {
return getMillisOf(this) < getMillisOf(when);
}
public boolean after(Date when) {
return getMillisOf(this) > getMillisOf(when);
}
public boolean equals(Object obj) {
return obj instanceof Date && getTime() == ((Date) obj).getTime();
}
static final long getMillisOf(Date date) {
if (date.cdate == null || date.cdate.isNormalized()) {
return date.fastTime;
}
BaseCalendar.Date d = (BaseCalendar.Date) date.cdate.clone();
return gcal.getTime(d);
}
public int compareTo(Date anotherDate) {
long thisTime = getMillisOf(this);
long anotherTime = getMillisOf(anotherDate);
return (thisTime<anotherTime ? -1 : (thisTime==anotherTime ? 0 : 1));
}
public int hashCode() {
long ht = this.getTime();
return (int) ht ^ (int) (ht >> 32);
}
public String toString() {
// "EEE MMM dd HH:mm:ss zzz yyyy";
BaseCalendar.Date date = normalize();
StringBuilder sb = new StringBuilder(28);
int index = date.getDayOfWeek();
if (index == BaseCalendar.SUNDAY) {
index = 8;
}
convertToAbbr(sb, wtb[index]).append(' '); // EEE
convertToAbbr(sb, wtb[date.getMonth() - 1 + 2 + 7]).append(' '); // MMM
CalendarUtils.sprintf0d(sb, date.getDayOfMonth(), 2).append(' '); // dd
CalendarUtils.sprintf0d(sb, date.getHours(), 2).append(':'); // HH
CalendarUtils.sprintf0d(sb, date.getMinutes(), 2).append(':'); // mm
CalendarUtils.sprintf0d(sb, date.getSeconds(), 2).append(' '); // ss
TimeZone zi = date.getZone();
if (zi != null) {
sb.append(zi.getDisplayName(date.isDaylightTime(), TimeZone.SHORT, Locale.US)); // zzz
} else {
sb.append("GMT");
}
sb.append(' ').append(date.getYear()); // yyyy
return sb.toString();
}
private static final StringBuilder convertToAbbr(StringBuilder sb, String name) {
sb.append(Character.toUpperCase(name.charAt(0)));
sb.append(name.charAt(1)).append(name.charAt(2));
return sb;
}
private final BaseCalendar.Date normalize() {
if (cdate == null) {
BaseCalendar cal = getCalendarSystem(fastTime);
cdate = (BaseCalendar.Date) cal.getCalendarDate(fastTime,
TimeZone.getDefaultRef());
return cdate;
}
// Normalize cdate with the TimeZone in cdate first. This is
// required for the compatible behavior.
if (!cdate.isNormalized()) {
cdate = normalize(cdate);
}
// If the default TimeZone has changed, then recalculate the
// fields with the new TimeZone.
TimeZone tz = TimeZone.getDefaultRef();
if (tz != cdate.getZone()) {
cdate.setZone(tz);
CalendarSystem cal = getCalendarSystem(cdate);
cal.getCalendarDate(fastTime, cdate);
}
return cdate;
}
// fastTime and the returned data are in sync upon return.
private final BaseCalendar.Date normalize(BaseCalendar.Date date) {
int y = date.getNormalizedYear();
int m = date.getMonth();
int d = date.getDayOfMonth();
int hh = date.getHours();
int mm = date.getMinutes();
int ss = date.getSeconds();
int ms = date.getMillis();
TimeZone tz = date.getZone();
// If the specified year can't be handled using a long value
// in milliseconds, GregorianCalendar is used for full
// compatibility with underflow and overflow. This is required
// by some JCK tests. The limits are based max year values -
// years that can be represented by max values of d, hh, mm,
// ss and ms. Also, let GregorianCalendar handle the default
// cutover year so that we don't need to worry about the
// transition here.
if (y == 1582 || y > 280000000 || y < -280000000) {
if (tz == null) {
tz = TimeZone.getTimeZone("GMT");
}
GregorianCalendar gc = new GregorianCalendar(tz);
gc.clear();
gc.set(GregorianCalendar.MILLISECOND, ms);
gc.set(y, m-1, d, hh, mm, ss);
fastTime = gc.getTimeInMillis();
BaseCalendar cal = getCalendarSystem(fastTime);
date = (BaseCalendar.Date) cal.getCalendarDate(fastTime, tz);
return date;
}
BaseCalendar cal = getCalendarSystem(y);
if (cal != getCalendarSystem(date)) {
date = (BaseCalendar.Date) cal.newCalendarDate(tz);
date.setNormalizedDate(y, m, d).setTimeOfDay(hh, mm, ss, ms);
}
// Perform the GregorianCalendar-style normalization.
fastTime = cal.getTime(date);
// In case the normalized date requires the other calendar
// system, we need to recalculate it using the other one.
BaseCalendar ncal = getCalendarSystem(fastTime);
if (ncal != cal) {
date = (BaseCalendar.Date) ncal.newCalendarDate(tz);
date.setNormalizedDate(y, m, d).setTimeOfDay(hh, mm, ss, ms);
fastTime = ncal.getTime(date);
}
return date;
}
private static final BaseCalendar getCalendarSystem(int year) {
if (year >= 1582) {
return gcal;
}
return getJulianCalendar();
}
private static final BaseCalendar getCalendarSystem(long utc) {
// Quickly check if the time stamp given by `utc' is the Epoch
// or later. If it's before 1970, we convert the cutover to
// local time to compare.
if (utc >= 0
|| utc >= GregorianCalendar.DEFAULT_GREGORIAN_CUTOVER
- TimeZone.getDefaultRef().getOffset(utc)) {
return gcal;
}
return getJulianCalendar();
}
private static final BaseCalendar getCalendarSystem(BaseCalendar.Date cdate) {
if (jcal == null) {
return gcal;
}
if (cdate.getEra() != null) {
return jcal;
}
return gcal;
}
synchronized private static final BaseCalendar getJulianCalendar() {
if (jcal == null) {
jcal = (BaseCalendar) CalendarSystem.forName("julian");
}
return jcal;
}
private void writeObject(ObjectOutputStream s)
throws IOException
{
s.writeLong(getTimeImpl());
}
private void readObject(ObjectInputStream s)
throws IOException, ClassNotFoundException
{
fastTime = s.readLong();
}
public static Date from(Instant instant) {
try {
return new Date(instant.toEpochMilli());
} catch (ArithmeticException ex) {
throw new IllegalArgumentException(ex);
}
}
public Instant toInstant() {
return Instant.ofEpochMilli(getTime());
}
}
Date常用函数
after(Date date)
该函数用来对比date是否比传入的参数when在时间上更晚，如果更晚则返回true，否则返回false。其中getMillisOf方法用来获取某Date对象储存的时间的时间戳。
before(Date date)
意义和上面的after()反过来
compareTo(Date date)
这个方法是为了sort（排序）方法服务的，compareTo方法的三种返回值（-1,0,1）的意义不在此赘述。此方法是通过比较两个date对象时间距离1970.1.1的毫秒数来确定谁大谁小的。
getTime()
其实就是返回保存了该Date对象时间戳的成员变量fastTime（该date对象时间距离1970.1.1的毫秒数）。
标注的Java类库包含两个类，一个是用来表示时间点的Date类，另一个是用来表示大家熟悉的日历表示法LocalDate类。
将时间与日历分开是一种很好的面向对象设计，通常，最好使用不同的类表示不同的概念。
public final class LocalDate
implements Temporal, TemporalAdjuster, ChronoLocalDate, Serializable {
/**
* 最小的LocalDate日期 '-999999999-01-01'.
* 表示过去很久
*/
public static final LocalDate MIN = LocalDate.of(Year.MIN_VALUE, 1, 1);
/**
* 最大的LocalDate日期'+999999999-12-31'
* 表示很久以后
*/
public static final LocalDate MAX = LocalDate.of(Year.MAX_VALUE, 12, 31);
/**
* Serialization version.
*/
private static final long serialVersionUID = 2942565459149668126L;
/**
* 400年是一个循环 共146097天
*/
private static final int DAYS_PER_CYCLE = 146097;
/**
* 计算0000-1970年共多少天，这里倒过来算即先算2000年的再回退30年
*/
static final long DAYS_0000_TO_1970 = (DAYS_PER_CYCLE * 5L) - (30L * 365L + 7L);
/**
* The year.
*/
private final int year;
/**
* The month-of-year.
*/
private final short month;
/**
* The day-of-month.
*/
private final short day;
//-----------------------------------------------------------------------
/**
* 获取本地系统时钟的时区
*/
public static LocalDate now() {
return now(Clock.systemDefaultZone());
}
/**
* 使用特定时区
*/
public static LocalDate now(ZoneId zone) {
return now(Clock.system(zone));
}
/**
* 获取当前日期，传入参数clock
*/
public static LocalDate now(Clock clock) {
Objects.requireNonNull(clock, "clock");
// inline to avoid creating object and Instant checks
final Instant now = clock.instant(); // called once
ZoneOffset offset = clock.getZone().getRules().getOffset(now);
long epochSec = now.getEpochSecond() + offset.getTotalSeconds(); // overflow caught later
long epochDay = Math.floorDiv(epochSec, SECONDS_PER_DAY);
return LocalDate.ofEpochDay(epochDay);
}
//-----------------------------------------------------------------------
/**
*用特定的年月日返回LocalDate,这里月份是Month类型，也就是英文的JUNE,MAY那些
*/
public static LocalDate of(int year, Month month, int dayOfMonth) {
YEAR.checkValidValue(year);
Objects.requireNonNull(month, "month");
DAY_OF_MONTH.checkValidValue(dayOfMonth);
return create(year, month.getValue(), dayOfMonth);
}
/**
*用特定的年月日返回LocalDate
*/
public static LocalDate of(int year, int month, int dayOfMonth) {
YEAR.checkValidValue(year);
MONTH_OF_YEAR.checkValidValue(month);
DAY_OF_MONTH.checkValidValue(dayOfMonth);
return create(year, month, dayOfMonth);
}
//-----------------------------------------------------------------------
/**
*用年和一年中的第几天来返回LocalDate
*/
public static LocalDate ofYearDay(int year, int dayOfYear) {
YEAR.checkValidValue(year);
DAY_OF_YEAR.checkValidValue(dayOfYear);
boolean leap = IsoChronology.INSTANCE.isLeapYear(year);
if (dayOfYear == 366 && leap == false) {
throw new DateTimeException("Invalid date 'DayOfYear 366' as '" + year + "' is not a leap year");
}
Month moy = Month.of((dayOfYear - 1) / 31 + 1);
int monthEnd = moy.firstDayOfYear(leap) + moy.length(leap) - 1;
if (dayOfYear > monthEnd) {
moy = moy.plus(1);
}
int dom = dayOfYear - moy.firstDayOfYear(leap) + 1;
return new LocalDate(year, moy.getValue(), dom);
}
//-----------------------------------------------------------------------
/**
* 用纪元时间来返回LocalDate。就是从1970-01-01
*/
public static LocalDate ofEpochDay(long epochDay) {
long zeroDay = epochDay + DAYS_0000_TO_1970;
// find the march-based year
zeroDay -= 60; // adjust to 0000-03-01 so leap day is at end of four year cycle
long adjust = 0;
if (zeroDay < 0) {
// adjust negative years to positive for calculation
long adjustCycles = (zeroDay + 1) / DAYS_PER_CYCLE - 1;
adjust = adjustCycles * 400;
zeroDay += -adjustCycles * DAYS_PER_CYCLE;
}
long yearEst = (400 * zeroDay + 591) / DAYS_PER_CYCLE;
long doyEst = zeroDay - (365 * yearEst + yearEst / 4 - yearEst / 100 + yearEst / 400);
if (doyEst < 0) {
// fix estimate
yearEst--;
doyEst = zeroDay - (365 * yearEst + yearEst / 4 - yearEst / 100 + yearEst / 400);
}
yearEst += adjust; // reset any negative year
int marchDoy0 = (int) doyEst;
// convert march-based values back to january-based
int marchMonth0 = (marchDoy0 * 5 + 2) / 153;
int month = (marchMonth0 + 2) % 12 + 1;
int dom = marchDoy0 - (marchMonth0 * 306 + 5) / 10 + 1;
yearEst += marchMonth0 / 10;
// check year now we are certain it is correct
int year = YEAR.checkValidIntValue(yearEst);
return new LocalDate(year, month, dom);
}
//-----------------------------------------------------------------------
/**
*
*/
public static LocalDate from(TemporalAccessor temporal) {
Objects.requireNonNull(temporal, "temporal");
LocalDate date = temporal.query(TemporalQueries.localDate());
if (date == null) {
throw new DateTimeException("Unable to obtain LocalDate from TemporalAccessor: " +
temporal + " of type " + temporal.getClass().getName());
}
return date;
}
//-----------------------------------------------------------------------
/**
* 解析像 {@code 2007-12-03} 格式的为LocalDate.实际底层封装了DateTimeFormatter.ISO_LOCAL_DATE格式也就是2007-12-03这种
*/
public static LocalDate parse(CharSequence text) {
return parse(text, DateTimeFormatter.ISO_LOCAL_DATE);
}
/**
* 传入一直预定义的DateTimeFormatter格式，进行解析返回LocalDate.可查看相关
*/
public static LocalDate parse(CharSequence text, DateTimeFormatter formatter) {
Objects.requireNonNull(formatter, "formatter");
return formatter.parse(text, LocalDate::from);
}
//-----------------------------------------------------------------------
/**
*私有方法返回传入年月日参数的LocalDate
*/
private static LocalDate create(int year, int month, int dayOfMonth) {
if (dayOfMonth > 28) {
int dom = 31;
switch (month) {
case 2:
dom = (IsoChronology.INSTANCE.isLeapYear(year) ? 29 : 28);
break;
case 4:
case 6:
case 9:
case 11:
dom = 30;
break;
}
if (dayOfMonth > dom) {
if (dayOfMonth == 29) {
throw new DateTimeException("Invalid date 'February 29' as '" + year + "' is not a leap year");
} else {
throw new DateTimeException("Invalid date '" + Month.of(month).name() + " " + dayOfMonth + "'");
}
}
}
return new LocalDate(year, month, dayOfMonth);
}
/**
* 判断传递的日期是否合理
*/
private static LocalDate resolvePreviousValid(int year, int month, int day) {
switch (month) {
case 2:
day = Math.min(day, IsoChronology.INSTANCE.isLeapYear(year) ? 29 : 28);
break;
case 4:
case 6:
case 9:
case 11:
day = Math.min(day, 30);
break;
}
return new LocalDate(year, month, day);
}
/**
* 私有的构造函数
*/
private LocalDate(int year, int month, int dayOfMonth) {
this.year = year;
this.month = (short) month;
this.day = (short) dayOfMonth;
}
//-----------------------------------------------------------------------
/**
* 检查特定的变量是否被支持，以下是支持的种类：
* <ul>
* <li>{@code DAY_OF_WEEK}
* <li>{@code ALIGNED_DAY_OF_WEEK_IN_MONTH}
* <li>{@code ALIGNED_DAY_OF_WEEK_IN_YEAR}
* <li>{@code DAY_OF_MONTH}
* <li>{@code DAY_OF_YEAR}
* <li>{@code EPOCH_DAY}
* <li>{@code ALIGNED_WEEK_OF_MONTH}
* <li>{@code ALIGNED_WEEK_OF_YEAR}
* <li>{@code MONTH_OF_YEAR}
* <li>{@code PROLEPTIC_MONTH}
* <li>{@code YEAR_OF_ERA}
* <li>{@code YEAR}
* <li>{@code ERA}
* </ul>
*对于非以上种类返回false
*/
@Override // override for Javadoc
public boolean isSupported(TemporalField field) {
return ChronoLocalDate.super.isSupported(field);
}
/**
* 检查特定的unit是否支持，如果不支持在进行plus，minus方法时会抛出异常
* 支持的单元有：
* <ul>
* <li>{@code DAYS}
* <li>{@code WEEKS}
* <li>{@code MONTHS}
* <li>{@code YEARS}
* <li>{@code DECADES}
* <li>{@code CENTURIES}
* <li>{@code MILLENNIA}
* <li>{@code ERAS}
* </ul>
* 其他类型会返回false
*/
@Override // override for Javadoc
public boolean isSupported(TemporalUnit unit) {
return ChronoLocalDate.super.isSupported(unit);
}
//-----------------------------------------------------------------------
/**
* 获取特定变量的合法值
*/
@Override
public ValueRange range(TemporalField field) {
if (field instanceof ChronoField) {
ChronoField f = (ChronoField) field;
if (f.isDateBased()) {
switch (f) {
case DAY_OF_MONTH: return ValueRange.of(1, lengthOfMonth());
case DAY_OF_YEAR: return ValueRange.of(1, lengthOfYear());
case ALIGNED_WEEK_OF_MONTH: return ValueRange.of(1, getMonth() == Month.FEBRUARY && isLeapYear() == false ? 4 : 5);
case YEAR_OF_ERA:
return (getYear() <= 0 ? ValueRange.of(1, Year.MAX_VALUE + 1) : ValueRange.of(1, Year.MAX_VALUE));
}
return field.range();
}
throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
}
return field.rangeRefinedBy(this);
}
/**
* 从特定的变量中取值返回int类型
*/
@Override // override for Javadoc and performance
public int get(TemporalField field) {
if (field instanceof ChronoField) {
return get0(field);
}
return ChronoLocalDate.super.get(field);
}
/**
* 从特定的变量中取值返回long类型
*/
@Override
public long getLong(TemporalField field) {
if (field instanceof ChronoField) {
if (field == EPOCH_DAY) {
return toEpochDay();
}
if (field == PROLEPTIC_MONTH) {
return getProlepticMonth();
}
return get0(field);
}
return field.getFrom(this);
}
private int get0(TemporalField field) {
switch ((ChronoField) field) {
case DAY_OF_WEEK: return getDayOfWeek().getValue();
case ALIGNED_DAY_OF_WEEK_IN_MONTH: return ((day - 1) % 7) + 1;
case ALIGNED_DAY_OF_WEEK_IN_YEAR: return ((getDayOfYear() - 1) % 7) + 1;
case DAY_OF_MONTH: return day;
case DAY_OF_YEAR: return getDayOfYear();
case EPOCH_DAY: throw new UnsupportedTemporalTypeException("Invalid field 'EpochDay' for get() method, use getLong() instead");
case ALIGNED_WEEK_OF_MONTH: return ((day - 1) / 7) + 1;
case ALIGNED_WEEK_OF_YEAR: return ((getDayOfYear() - 1) / 7) + 1;
case MONTH_OF_YEAR: return month;
case PROLEPTIC_MONTH: throw new UnsupportedTemporalTypeException("Invalid field 'ProlepticMonth' for get() method, use getLong() instead");
case YEAR_OF_ERA: return (year >= 1 ? year : 1 - year);
case YEAR: return year;
case ERA: return (year >= 1 ? 1 : 0);
}
throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
}
private long getProlepticMonth() {
return (year * 12L + month - 1);
}
//-----------------------------------------------------------------------
/**
* 获取数据的年表，ISO日历系统标准
*/
@Override
public IsoChronology getChronology() {
return IsoChronology.INSTANCE;
}
/**
* 获取时间的era，像BE.AD这些（公元，公元前...）
*/
@Override // override for Javadoc
public Era getEra() {
return ChronoLocalDate.super.getEra();
}
/**
* 获取年
*/
public int getYear() {
return year;
}
/**
* 获取月份
*/
public int getMonthValue() {
return month;
}
/**
* 获取英文的那种月份
*/
public Month getMonth() {
return Month.of(month);
}
/**
* 获取日
*/
public int getDayOfMonth() {
return day;
}
/**
* 获取一年中的第几天
*/
public int getDayOfYear() {
return getMonth().firstDayOfYear(isLeapYear()) + day - 1;
}
/**
* 获取1周中的第几天
*/
public DayOfWeek getDayOfWeek() {
int dow0 = (int)Math.floorMod(toEpochDay() + 3, 7);
return DayOfWeek.of(dow0 + 1);
}
//-----------------------------------------------------------------------
/**
* 判断是否是闰年
*/
@Override // override for Javadoc and performance
public boolean isLeapYear() {
return IsoChronology.INSTANCE.isLeapYear(year);
}
/**
* 返回月份的长度
*/
@Override
public int lengthOfMonth() {
switch (month) {
case 2:
return (isLeapYear() ? 29 : 28);
case 4:
case 6:
case 9:
case 11:
return 30;
default:
return 31;
}
}
/**
* 返回年的长度
public int lengthOfYear() {
return (isLeapYear() ? 366 : 365);
}
//-----------------------------------------------------------------------
/**
* 返回一个调整过的LocalDate类型，这些adjuster是预定义的
*/
@Override
public LocalDate with(TemporalAdjuster adjuster) {
// optimizations
if (adjuster instanceof LocalDate) {
return (LocalDate) adjuster;
}
return (LocalDate) adjuster.adjustInto(this);
}
/**
* 返回一个调整过的LocalDate类型，这些adjuster是预定义的，传入一个新的值
*/
@Override
public LocalDate with(TemporalField field, long newValue) {
if (field instanceof ChronoField) {
ChronoField f = (ChronoField) field;
f.checkValidValue(newValue);
switch (f) {
case DAY_OF_WEEK: return plusDays(newValue - getDayOfWeek().getValue());
case ALIGNED_DAY_OF_WEEK_IN_MONTH: return plusDays(newValue - getLong(ALIGNED_DAY_OF_WEEK_IN_MONTH));
case ALIGNED_DAY_OF_WEEK_IN_YEAR: return plusDays(newValue - getLong(ALIGNED_DAY_OF_WEEK_IN_YEAR));
case DAY_OF_MONTH: return withDayOfMonth((int) newValue);
case DAY_OF_YEAR: return withDayOfYear((int) newValue);
case EPOCH_DAY: return LocalDate.ofEpochDay(newValue);
case ALIGNED_WEEK_OF_MONTH: return plusWeeks(newValue - getLong(ALIGNED_WEEK_OF_MONTH));
case ALIGNED_WEEK_OF_YEAR: return plusWeeks(newValue - getLong(ALIGNED_WEEK_OF_YEAR));
case MONTH_OF_YEAR: return withMonth((int) newValue);
case PROLEPTIC_MONTH: return plusMonths(newValue - getProlepticMonth());
case YEAR_OF_ERA: return withYear((int) (year >= 1 ? newValue : 1 - newValue));
case YEAR: return withYear((int) newValue);
case ERA: return (getLong(ERA) == newValue ? this : withYear(1 - year));
}
throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
}
return field.adjustInto(this, newValue);
}
//-----------------------------------------------------------------------
/**
* 改年返回新的LocalDate
*/
public LocalDate withYear(int year) {
if (this.year == year) {
return this;
}
YEAR.checkValidValue(year);
return resolvePreviousValid(year, month, day);
}
/**
* 改月返回新的LocalDate
*/
public LocalDate withMonth(int month) {
if (this.month == month) {
return this;
}
MONTH_OF_YEAR.checkValidValue(month);
return resolvePreviousValid(year, month, day);
}
/**
*改日返回新的LocalDate
*/
public LocalDate withDayOfMonth(int dayOfMonth) {
if (this.day == dayOfMonth) {
return this;
}
return of(year, month, dayOfMonth);
}
/**
* 改一年中第几日返回新的LocalDate
*/
public LocalDate withDayOfYear(int dayOfYear) {
if (this.getDayOfYear() == dayOfYear) {
return this;
}
return ofYearDay(year, dayOfYear);
}
//-----------------------------------------------------------------------
/**
* 返回新的LocalDate，在原值上进行 加 操作
*/
@Override
public LocalDate plus(TemporalAmount amountToAdd) {
if (amountToAdd instanceof Period) {
Period periodToAdd = (Period) amountToAdd;
return plusMonths(periodToAdd.toTotalMonths()).plusDays(periodToAdd.getDays());
}
Objects.requireNonNull(amountToAdd, "amountToAdd");
return (LocalDate) amountToAdd.addTo(this);
}
/**
* 返回新的LocalDate，在原值上进行 加 操作
/
@Override
public LocalDate plus(long amountToAdd, TemporalUnit unit) {
if (unit instanceof ChronoUnit) {
ChronoUnit f = (ChronoUnit) unit;
switch (f) {
case DAYS: return plusDays(amountToAdd);
case WEEKS: return plusWeeks(amountToAdd);
case MONTHS: return plusMonths(amountToAdd);
case YEARS: return plusYears(amountToAdd);
case DECADES: return plusYears(Math.multiplyExact(amountToAdd, 10));
case CENTURIES: return plusYears(Math.multiplyExact(amountToAdd, 100));
case MILLENNIA: return plusYears(Math.multiplyExact(amountToAdd, 1000));
case ERAS: return with(ERA, Math.addExact(getLong(ERA), amountToAdd));
}
throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
}
return unit.addTo(this, amountToAdd);
}
//-----------------------------------------------------------------------
/**
* 在原本基础上对年添加传入值后返回一个LocalDate
*/
public LocalDate plusYears(long yearsToAdd) {
if (yearsToAdd == 0) {
return this;
}
int newYear = YEAR.checkValidIntValue(year + yearsToAdd); // safe overflow
return resolvePreviousValid(newYear, month, day);
}
/**
* 在原本基础上对月添加传入值后返回一个LocalDate
*/
public LocalDate plusMonths(long monthsToAdd) {
if (monthsToAdd == 0) {
return this;
}
long monthCount = year * 12L + (month - 1);
long calcMonths = monthCount + monthsToAdd; // safe overflow
int newYear = YEAR.checkValidIntValue(Math.floorDiv(calcMonths, 12));
int newMonth = (int)Math.floorMod(calcMonths, 12) + 1;
return resolvePreviousValid(newYear, newMonth, day);
}
/**
* 在原本基础上对周添加传入值后返回一个LocalDate，底层调用的是加7天
*/
public LocalDate plusWeeks(long weeksToAdd) {
return plusDays(Math.multiplyExact(weeksToAdd, 7));
}
/**
* 在原本基础上对日添加传入值后返回一个LocalDate
*/
public LocalDate plusDays(long daysToAdd) {
if (daysToAdd == 0) {
return this;
}
long mjDay = Math.addExact(toEpochDay(), daysToAdd);
return LocalDate.ofEpochDay(mjDay);
}
//-----------------------------------------------------------------------
/**
* 减，底层调用的还是plus相关的方法，传入的是实际上是负值
*/
@Override
public LocalDate minus(TemporalAmount amountToSubtract) {
if (amountToSubtract instanceof Period) {
Period periodToSubtract = (Period) amountToSubtract;
return minusMonths(periodToSubtract.toTotalMonths()).minusDays(periodToSubtract.getDays());
}
Objects.requireNonNull(amountToSubtract, "amountToSubtract");
return (LocalDate) amountToSubtract.subtractFrom(this);
}
@Override
public LocalDate minus(long amountToSubtract, TemporalUnit unit) {
return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
}
public LocalDate minusYears(long yearsToSubtract) {
return (yearsToSubtract == Long.MIN_VALUE ? plusYears(Long.MAX_VALUE).plusYears(1) : plusYears(-yearsToSubtract));
}
public LocalDate minusMonths(long monthsToSubtract) {
return (monthsToSubtract == Long.MIN_VALUE ? plusMonths(Long.MAX_VALUE).plusMonths(1) : plusMonths(-monthsToSubtract));
}
public LocalDate minusWeeks(long weeksToSubtract) {
return (weeksToSubtract == Long.MIN_VALUE ? plusWeeks(Long.MAX_VALUE).plusWeeks(1) : plusWeeks(-weeksToSubtract));
}
public LocalDate minusDays(long daysToSubtract) {
return (daysToSubtract == Long.MIN_VALUE ? plusDays(Long.MAX_VALUE).plusDays(1) : plusDays(-daysToSubtract));
}
//-----------------------------------------------------------------------
/**
* 特定查询
*/
@SuppressWarnings("unchecked")
@Override
public <R> R query(TemporalQuery<R> query) {
if (query == TemporalQueries.localDate()) {
return (R) this;
}
return ChronoLocalDate.super.query(query);
}
/**
*
* <pre>
* // 下面两种是相同的，但推荐第二种
* temporal = thisLocalDate.adjustInto(temporal);
* temporal = temporal.with(thisLocalDate);
* </pre>
*
*/
@Override // override for Javadoc
public Temporal adjustInto(Temporal temporal) {
return ChronoLocalDate.super.adjustInto(temporal);
}
@Override
public long until(Temporal endExclusive, TemporalUnit unit) {
LocalDate end = LocalDate.from(endExclusive);
if (unit instanceof ChronoUnit) {
switch ((ChronoUnit) unit) {
case DAYS: return daysUntil(end);
case WEEKS: return daysUntil(end) / 7;
case MONTHS: return monthsUntil(end);
case YEARS: return monthsUntil(end) / 12;
case DECADES: return monthsUntil(end) / 120;
case CENTURIES: return monthsUntil(end) / 1200;
case MILLENNIA: return monthsUntil(end) / 12000;
case ERAS: return end.getLong(ERA) - getLong(ERA);
}
throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
}
return unit.between(this, end);
}
long daysUntil(LocalDate end) {
return end.toEpochDay() - toEpochDay(); // no overflow
}
private long monthsUntil(LocalDate end) {
long packed1 = getProlepticMonth() * 32L + getDayOfMonth(); // no overflow
long packed2 = end.getProlepticMonth() * 32L + end.getDayOfMonth(); // no overflow
return (packed2 - packed1) / 32;
}
@Override
public Period until(ChronoLocalDate endDateExclusive) {
LocalDate end = LocalDate.from(endDateExclusive);
long totalMonths = end.getProlepticMonth() - this.getProlepticMonth(); // safe
int days = end.day - this.day;
if (totalMonths > 0 && days < 0) {
totalMonths--;
LocalDate calcDate = this.plusMonths(totalMonths);
days = (int) (end.toEpochDay() - calcDate.toEpochDay()); // safe
} else if (totalMonths < 0 && days > 0) {
totalMonths++;
days -= end.lengthOfMonth();
}
long years = totalMonths / 12; // safe
int months = (int) (totalMonths % 12); // safe
return Period.of(Math.toIntExact(years), months, days);
}
/**
* 用特定的格式格式化日期
*/
@Override // override for Javadoc and performance
public String format(DateTimeFormatter formatter) {
Objects.requireNonNull(formatter, "formatter");
return formatter.format(this);
}
//-----------------------------------------------------------------------
/**
* 结合时间格式LocalTime，返回一个LocalDateTime对象
*/
@Override
public LocalDateTime atTime(LocalTime time) {
return LocalDateTime.of(this, time);
}
/**
* 结合时间格式： 时 分，返回一个LocalDateTime对象
*/
public LocalDateTime atTime(int hour, int minute) {
return atTime(LocalTime.of(hour, minute));
}
/**
* 结合时分秒，返回一个LocalDateTime对象
*/
public LocalDateTime atTime(int hour, int minute, int second) {
return atTime(LocalTime.of(hour, minute, second));
}
/**
* 结合时分秒 纳秒，返回一个LocalDateTime对象
*/
public LocalDateTime atTime(int hour, int minute, int second, int nanoOfSecond) {
return atTime(LocalTime.of(hour, minute, second, nanoOfSecond));
}
/**
* 结合一个OffsetTime格式，返回一个OffsetTime对象。OffsetTime表示具有相对于UTC的固定区偏移的时间。
*/
public OffsetDateTime atTime(OffsetTime time) {
return OffsetDateTime.of(LocalDateTime.of(this, time.toLocalTime()), time.getOffset());
}
/**
* 结合午夜时间0点返回一个LocalDateTime对象
*/
public LocalDateTime atStartOfDay() {
return LocalDateTime.of(this, LocalTime.MIDNIGHT);
}
/**
* 传入时区id，返回一个ZonedDateTime
*/
public ZonedDateTime atStartOfDay(ZoneId zone) {
Objects.requireNonNull(zone, "zone");
// need to handle case where there is a gap from 11:30 to 00:30
// standard ZDT factory would result in 01:00 rather than 00:30
LocalDateTime ldt = atTime(LocalTime.MIDNIGHT);
if (zone instanceof ZoneOffset == false) {
ZoneRules rules = zone.getRules();
ZoneOffsetTransition trans = rules.getTransition(ldt);
if (trans != null && trans.isGap()) {
ldt = trans.getDateTimeAfter();
}
}
return ZonedDateTime.of(ldt, zone);
}
//-----------------------------------------------------------------------
@Override
public long toEpochDay() {
long y = year;
long m = month;
long total = 0;
total += 365 * y;
if (y >= 0) {
total += (y + 3) / 4 - (y + 99) / 100 + (y + 399) / 400;
} else {
total -= y / -4 - y / -100 + y / -400;
}
total += ((367 * m - 362) / 12);
total += day - 1;
if (m > 2) {
total--;
if (isLeapYear() == false) {
total--;
}
}
return total - DAYS_0000_TO_1970;
}
//-----------------------------------------------------------------------
/**
* 和另一个日期的年月日进行比较判断
*/
@Override // override for Javadoc and performance
public int compareTo(ChronoLocalDate other) {
if (other instanceof LocalDate) {
return compareTo0((LocalDate) other);
}
return ChronoLocalDate.super.compareTo(other);
}
int compareTo0(LocalDate otherDate) {
int cmp = (year - otherDate.year);
if (cmp == 0) {
cmp = (month - otherDate.month);
if (cmp == 0) {
cmp = (day - otherDate.day);
}
}
return cmp;
}
/**
* 判断一个日期是否在另一个之后
*/
@Override // override for Javadoc and performance
public boolean isAfter(ChronoLocalDate other) {
if (other instanceof LocalDate) {
return compareTo0((LocalDate) other) > 0;
}
return ChronoLocalDate.super.isAfter(other);
}
/**
* 判断一个日期是否在另一个日期之前
*/
@Override // override for Javadoc and performance
public boolean isBefore(ChronoLocalDate other) {
if (other instanceof LocalDate) {
return compareTo0((LocalDate) other) < 0;
}
return ChronoLocalDate.super.isBefore(other);
}
/**
* 判断一个日期是否在另一个之前
*/
@Override // override for Javadoc and performance
public boolean isEqual(ChronoLocalDate other) {
if (other instanceof LocalDate) {
return compareTo0((LocalDate) other) == 0;
}
return ChronoLocalDate.super.isEqual(other);
}
//-----------------------------------------------------------------------
/**
* 重写object的equals方法，判断与对象obj是否相等
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj instanceof LocalDate) {
return compareTo0((LocalDate) obj) == 0;
}
return false;
}
/**
* 重写object的hashcode方法
*/
@Override
public int hashCode() {
int yearValue = year;
int monthValue = month;
int dayValue = day;
return (yearValue & 0xFFFFF800) ^ ((yearValue << 11) + (monthValue << 6) + (dayValue));
}
//-----------------------------------------------------------------------
/**
*重写toString方法，返回格式： {@code 2007-12-03}.
*
*/
@Override
public String toString() {
int yearValue = year;
int monthValue = month;
int dayValue = day;
int absYear = Math.abs(yearValue);
StringBuilder buf = new StringBuilder(10);
if (absYear < 1000) {
if (yearValue < 0) {
buf.append(yearValue - 10000).deleteCharAt(1);
} else {
buf.append(yearValue + 10000).deleteCharAt(0);
}
} else {
if (yearValue > 9999) {
buf.append('+');
}
buf.append(yearValue);
}
return buf.append(monthValue < 10 ? "-0" : "-")
.append(monthValue)
.append(dayValue < 10 ? "-0" : "-")
.append(dayValue)
.toString();
}
private Object writeReplace() {
return new Ser(Ser.LOCAL_DATE_TYPE, this);
}
private void readObject(ObjectInputStream s) throws InvalidObjectException {
throw new InvalidObjectException("Deserialization via serialization delegate");
}
void writeExternal(DataOutput out) throws IOException {
out.writeInt(year);
out.writeByte(month);
out.writeByte(day);
}
static LocalDate readExternal(DataInput in) throws IOException {
int year = in.readInt();
int month = in.readByte();
int dayOfMonth = in.readByte();
return LocalDate.of(year, month, dayOfMonth);
}
}
原文链接：https://blog.csdn.net/sayWhat_sayHello/article/details/80418498不要使用构造器来构造LocalDate类的对象。实际上，应该使用静态工厂方法代表调用构造器
LocalDate.now();
可以提供年月日来构造一个特定日期的对象，LocalDate newYearValue = LocalDate.of(1999，12，31)
一旦有了LocalDate对象，可以使用getYear、getMonthValue、getDayOfMonth得到年月日。
newYearValue .plusDays(1000)会得到一个新的日期对象，距离当前日期指定天数的一个新日期。
显示当前月的日历
