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Calendar now = Calendar.getInstance();
set(int year ,int month,int date)
set(int year ,int month,int date,int hour,int minute)
set(int year ,int month,int date,int hour,int minute,int second)
Now.get(Calendar.Month) 这样的方法 0表示一月,1表示二月
get(Calendar.DAY_OF_MONTH)获得这个月的第几天
get(Calendar.DAY_OF_WEEK)获得这个星期的第几天
get(Calendar.DAY_OF_YEAR)获得这个年的第几天
getTimeMillis()获得当前时间的毫秒表示
abstract void add(int field, int amount)
boolean after(Object when)
boolean before(Object when)
void clear()
void clear(int field)
Object clone()
int compareTo(Calendar anotherCalendar)
protected void complete()
protected abstract void computeFields()
protected abstract void computeTime()
boolean equals(Object obj)
int get(int field)
int getActualMaximum(int field)
int getActualMinimum(int field)
static Locale[] getAvailableLocales()
String getDisplayName(int field, int style, Locale locale)
Map<String,Integer> getDisplayNames(int field, int style, Locale locale)
int getFirstDayOfWeek()
abstract int getGreatestMinimum(int field)
static Calendar getInstance()
static Calendar getInstance(Locale aLocale)
static Calendar getInstance(TimeZone zone)
static Calendar getInstance(TimeZone zone, Locale aLocale)
abstract int getLeastMaximum(int field)
返回此 Calendarabstract int getMaximum(int field)
int getMinimalDaysInFirstWeek()
abstract int getMinimum(int field)
Date getTime()
long getTimeInMillis()
TimeZone getTimeZone()
int hashCode()
protected int internalGet(int field)
boolean isLenient()
boolean isSet(int field)
abstract void roll(int field, boolean up)
void roll(int field, int amount)
void set(int field, int value)
void set(int year, int month, int date)
void set(int year, int month, int date, int hourOfDay, int minute)
void set(int year, int month, int date, int hourOfDay, int minute, int second)
void setFirstDayOfWeek(int value)
void setLenient(boolean lenient)
void setMinimalDaysInFirstWeek(int value)
void setTime(Date date)
void setTimeInMillis(long millis)
void setTimeZone(TimeZone value)
String toString()
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,必须先clear一下,否则很多信息会继承自系统当前时间
Calendar和Date的转化
Calendar cal=Calendar.getInstance();
Date date=cal.getTime();
Date date=new Date();
Calendar cal=Calendar.getInstance();
cal.setTime(date);
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));
计算一年中的第几星期
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH, 8);
cal.set(Calendar.DAY_OF_MONTH, 3);
int weekno=cal.get(Calendar.WEEK_OF_YEAR);
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
add()和roll()的用法
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH, 8);
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
2006-09-03
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH, 8);
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:
2006-09-29
2006-09-03
可见,roll()方法在本月内循环,一般使用add()方法;
计算两个任意时间中间的间隔天数
/
**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));
}
/**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:
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;
}
2020年10月7日更
大家觉得写还可以,可以点赞、收藏、关注一下吧!
也可以到我的个人博客参观一下,估计近几年都会一直更新!和我做个朋友吧!https://motongxue.cn