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📜  Java Calendar类

📅  最后修改于: 2020-10-01 06:44:39             🧑  作者: Mango

Java Calendar类

Java Calendar类是一个抽象类，它提供在特定时间点和一组日历字段(例如MONTH，YEAR，HOUR等)之间转换日期的方法。它继承了Object类并实现Comparable接口。

Java Calendar类声明

让我们看看java.util.Calendar类的声明。

public abstract class Calendar extends Object 
implements Serializable, Cloneable, Comparable

日历方法清单

No Method Description
1. public void add(int field, int amount) Adds the specified (signed) amount of time to the given calendar field.
2. public boolean after (Object when) The method Returns true if the time represented by this Calendar is after the time represented by when Object.
3. public boolean before(Object when) The method Returns true if the time represented by this Calendar is before the time represented by when Object.
4. public final void clear(int field) Set the given calendar field value and the time value of this Calendar undefined.
5. public Object clone() Clone method provides the copy of the current object.
6. public int compareTo(Calendar anotherCalendar) The compareTo() method of Calendar class compares the time values (millisecond offsets) between two calendar object.
7. protected void complete() It fills any unset fields in the calendar fields.
8. protected abstract void computeFields() It converts the current millisecond time value time to calendar field values in fields[].
9. protected abstract void computeTime() It converts the current calendar field values in fields[] to the millisecond time value time.
10. public boolean equals(Object object) The equals() method compares two objects for equality and Returns true if they are equal.
11. public int get(int field) In get() method fields of the calendar are passed as the parameter, and this method Returns the value of fields passed as the parameter.
12. public int getActualMaximum(int field) Returns the Maximum possible value of the calendar field passed as the parameter to getActualMaximum() method.
13. public int getActualMinimum(int field) Returns the Minimum possible value of the calendar field passed as parameter to getActualMinimum() methot.
14. public static Set getAvailableCalendarTypes() Returns a set which contains string set of all available calendar type supported by Java Runtime Environment.
15. public static Locale[] getAvailableLocales() Returns an array of all locales available in java runtime environment.
16. public String getCalendarType() Returns in string all available calendar type supported by Java Runtime Environment.
17. public String getDisplayName(int field, int style, Locale locale) Returns the String representation of the calendar field value passed as the parameter in a given style and local.
18. public Map getDisplayNames(int field, int style, Locale locale) Returns Map representation of the calendar field value passed as the parameter in a given style and local.
19. public int getFirstDayOfWeek() Returns the first day of the week in integer form.
20. public abstract int getGreatestMinimum(int field) This method returns the highest minimum value of Calendar field passed as the parameter.
21. public static Calendar getInstance() This method is used with calendar object to get the instance of calendar according to current time zone set by java runtime environment
22. public abstract int getLeastMaximum(int field) Returns smallest value from all maximum value for the field specified as the parameter to the method.
23. public abstract int getMaximum(int field) This method is used with calendar object to get the maximum value of the specified calendar field as the parameter.
24. public int getMinimalDaysInFirstWeek() Returns required minimum days in integer form.
25. public abstract int getMinimum(int field) This method is used with calendar object to get the minimum value of specified calendar field as the parameter.
26. public final Date getTime() This method gets the time value of calendar object and Returns date.
27. public long getTimeInMillis() Returns the current time in millisecond. This method has long as return type.
28. public TimeZone getTimeZone() This method gets the TimeZone of calendar object and Returns a TimeZone object.
29. public int getWeeksInWeekYear() Return total weeks in week year. Weeks in week year is returned in integer form.
30. public int getWeekYear() This method gets the week year represented by current Calendar.
31. public int hashCode() All other classes in Java overload hasCode() method. This method Returns the hash code for calendar object.
32. protected final int internalGet(int field) This method returns the value of the calendar field passed as the parameter.
33. Public boolean isLenient() Return Boolean value. True if the interpretation mode of this calendar is lenient; false otherwise.
34. public final boolean isSet(int field) This method checks if specified field as the parameter has been set or not. If not set then it returns false otherwise true.
35. public boolean isWeekDateSupported() Checks if this calendar supports week date. The default value is false.
36. public abstract void roll(int field, boolean up) This method increase or decrease the specified calendar field by one unit without affecting the other field
37. public void set(int field, int value) Sets the specified calendar field by the specified value.
38. public void setFirstDayOfWeek(int value) Sets the first day of the week. The value which is to be set as the first day of the week is passed as parameter.
39. public void setMinimalDaysInFirstWeek(int value) Sets the minimal days required in the first week. The value which is to be set as minimal days in first week is passed as parameter.
40. public final void setTime(Date date) Sets the Time of current calendar object. A Date object id passed as the parameter.
41. public void setTimeInMillis(long millis) Sets the current time in millisecond.
42. public void setTimeZone(TimeZone value) Sets the TimeZone with passed TimeZone value (object) as the parameter.
43. public void setWeekDate(int weekYear, int weekOfYear, int dayOfWeek) Sets the current date with specified integer value as the parameter. These values are weekYear, weekOfYear and dayOfWeek.
44. public final Instant toInstant() The toInstant() method convert the current object to an instant.
45. public String toString() Returns string representation of the current object.

Java Calendar类示例

import java.util.Calendar;
public class CalendarExample1 {
   public static void main(String[] args) {
   Calendar calendar = Calendar.getInstance();
   System.out.println("The current date is : " + calendar.getTime());
   calendar.add(Calendar.DATE, -15);
   System.out.println("15 days ago: " + calendar.getTime());
   calendar.add(Calendar.MONTH, 4);
   System.out.println("4 months later: " + calendar.getTime());
   calendar.add(Calendar.YEAR, 2);
   System.out.println("2 years later: " + calendar.getTime());
   }
}

输出：

The current date is : Thu Jan 19 18:47:02 IST 2017
15 days ago: Wed Jan 04 18:47:02 IST 2017
4 months later: Thu May 04 18:47:02 IST 2017
2 years later: Sat May 04 18:47:02 IST 2019

Java Calendar类示例：get()

import java.util.*;
public class CalendarExample2{
  public static void main(String[] args) {
   Calendar calendar = Calendar.getInstance();
   System.out.println("At present Calendar's Year: " + calendar.get(Calendar.YEAR));
   System.out.println("At present Calendar's Day: " + calendar.get(Calendar.DATE));
   }
}

输出：

At present Calendar's Year: 2017
At present Calendar's Day: 20

Java Calendar类示例：getInstance()

import java.util.*;
public class CalendarExample3{
   public static void main(String[] args) {
   Calendar calendar = Calendar.getInstance();
   System.out.print("At present Date And Time Is: " + calendar.getTime());
   }
}

输出：

At present Date And Time Is: Fri Jan 20 14:26:19 IST 2017

Java Calendar类示例：getMaximum()

import java.util.*;
public class CalendarExample4 {
   public static void main(String[] args) {
   Calendar calendar = Calendar.getInstance();
   int maximum = calendar.getMaximum(Calendar.DAY_OF_WEEK);
   System.out.println("Maximum number of days in week: " + maximum);
   maximum = calendar.getMaximum(Calendar.WEEK_OF_YEAR);
   System.out.println("Maximum number of weeks in year: " + maximum);
   }
}

输出：

Maximum number of days in week: 7
Maximum number of weeks in year: 53

Java Calendar类示例：getMinimum()

import java.util.*;
public class CalendarExample5 {
   public static void main(String[] args) {
   Calendar cal = Calendar.getInstance();
   int maximum = cal.getMinimum(Calendar.DAY_OF_WEEK);
   System.out.println("Minimum number of days in week: " + maximum);
   maximum = cal.getMinimum(Calendar.WEEK_OF_YEAR);
   System.out.println("Minimum number of weeks in year: " + maximum);
   }
}

输出：

Minimum number of days in week: 1
Minimum number of weeks in year: 1