JAVA中的日期用Date.before()和Date.after(),还是直接Date.getTime比较,哪个好?
根据 OpenJDK 7 的源代码:
public boolean before(Date when) {
return getMillisOf(this) < getMillisOf(when);
}
public boolean after(Date when) {
return getMillisOf(this) > getMillisOf(when);
}
public long getTime() {
return getTimeImpl();
}
private final long getTimeImpl() {
if (cdate != null && !cdate.isNormalized()) {
normalize();
}
return fastTime;
}
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);
}
private final BaseCalendar.Date normalize() {
if (cdate == null) {
BaseCalendar cal = getCalendarSystem(fastTime);
cdate = (BaseCalendar.Date) cal.getCalendarDate(fastTime, TimeZone.getDefaultRef());
return cdate;
}
if (!cdate.isNormalized()) {
cdate = normalize(cdate);
}
TimeZone tz = TimeZone.getDefaultRef();
if (tz != cdate.getZone()) {
cdate.setZone(tz);
CalendarSystem cal = getCalendarSystem(cdate);
cal.getCalendarDate(fastTime, cdate);
}
return cdate;
}
看起来 before
和 after
会稍微快一点点。不过也有的 Java 实现里面 before
和 after
就是调用 getTime()
的。