请参考一个书上的:
注意其中的daysBetween()方法。package corejava;import java.util.*;
import java.io.*;/**
Stores dates and perform date arithmetic. This is another date class, but more convenient that
<tt>java.util.Date</tt> or <tt>java.util.Calendar</tt> @version 1.20 5 Oct 1998
@author Cay Horstmann
*/public class Day implements Cloneable, Serializable
{ /**
Constructs today's date
*/
public Day()
{ GregorianCalendar todaysDate
= new GregorianCalendar();
year = todaysDate.get(Calendar.YEAR);
month = todaysDate.get(Calendar.MONTH) + 1;
day = todaysDate.get(Calendar.DAY_OF_MONTH);
} /**
Constructs a specific date @param yyyy year (full year, e.g., 1996,
<i>not</i> starting from 1900)
@param m month
@param d day
@exception IllegalArgumentException if yyyy m d not a
valid date
*/
public Day(int yyyy, int m, int d)
{ year = yyyy;
month = m;
day = d;
if (!isValid())
throw new IllegalArgumentException();
}
/**
Advances this day by n days. For example.
d.advance(30) adds thirdy days to d @param n the number of days by which to change this
day (can be < 0)
*/
public void advance(int n)
{ fromJulian(toJulian() + n);
} /**
Gets the day of the month @return the day of the month (1...31)
*/ public int getDay()
{ return day;
} /**
Gets the month
@return the month (1...12)
*/ public int getMonth() { return month;
} /**
Gets the year
@return the year (counting from 0, <i>not</i> from 1900)
*/ public int getYear()
{ return year;
}
/**
Gets the weekday
@return the weekday ({@link Day#SUNDAY}, ...,
{@link Day#SATURDAY})
*/
public int weekday()
{ return (toJulian() + 1) % 7 + 1;
}
/**
The number of days between this and day parameter
@param b any date
@return the number of days between this and day parameter
and b (> 0 if this day comes after b)
*/
public int daysBetween(Day b)
{ return toJulian() - b.toJulian();
} /**
A string representation of the day
@return a string representation of the day
*/
public String toString()
{ return "Day[" + year + "," + month + "," + day + "]";
} /**
Makes a bitwise copy of a Day object
@return a bitwise copy of a Day object
*/
public Object clone()
{ try
{ return super.clone();
} catch (CloneNotSupportedException e)
{ // this shouldn't happen, since we are Cloneable
return null;
}
} /**
Compares this Day against another object
@param obj another object
@return true if the other object is identical to this Day object
*/ public boolean equals(Object obj)
{ if (!getClass().equals(obj.getClass())) return false;
Day b = (Day)obj;
return day == b.day && month == b.month && year == b.year;
} /**
Computes the number of days between two dates
@return true iff this is a valid date
*/
private boolean isValid()
{ Day t = new Day();
t.fromJulian(this.toJulian());
return t.day == day && t.month == month
&& t.year == year;
} /**
@return The Julian day number that begins at noon of
this day
Positive year signifies A.D., negative year B.C.
Remember that the year after 1 B.C. was 1 A.D. A convenient reference point is that May 23, 1968 noon
is Julian day 2440000. Julian day 0 is a Monday. This algorithm is from Press et al., Numerical Recipes
in C, 2nd ed., Cambridge University Press 1992
*/ private int toJulian()
{ int jy = year;
if (year < 0) jy++;
int jm = month;
if (month > 2) jm++;
else
{ jy--;
jm += 13;
}
int jul = (int) (java.lang.Math.floor(365.25 * jy)
+ java.lang.Math.floor(30.6001*jm) + day + 1720995.0); int IGREG = 15 + 31*(10+12*1582);
// Gregorian Calendar adopted Oct. 15, 1582 if (day + 31 * (month + 12 * year) >= IGREG)
// change over to Gregorian calendar
{ int ja = (int)(0.01 * jy);
jul += 2 - ja + (int)(0.25 * ja);
}
return jul;
} /**
Converts a Julian day to a calendar date This algorithm is from Press et al., Numerical Recipes
in C, 2nd ed., Cambridge University Press 1992
@param j the Julian date
*/ private void fromJulian(int j)
{ int ja = j;
int JGREG = 2299161;
/* the Julian date of the adoption of the Gregorian
calendar
*/ if (j >= JGREG)
/* cross-over to Gregorian Calendar produces this
correction
*/
{ int jalpha = (int)(((float)(j - 1867216) - 0.25)
/ 36524.25);
ja += 1 + jalpha - (int)(0.25 * jalpha);
}
int jb = ja + 1524;
int jc = (int)(6680.0 + ((float)(jb-2439870) - 122.1)
/365.25);
int jd = (int)(365 * jc + (0.25 * jc));
int je = (int)((jb - jd)/30.6001);
day = jb - jd - (int)(30.6001 * je);
month = je - 1;
if (month > 12) month -= 12;
year = jc - 4715;
if (month > 2) --year;
if (year <= 0) --year;
} public static int SUNDAY = 1;
public static int MONDAY = 2;
public static int TUESDAY = 3;
public static int WEDNESDAY = 4;
public static int THURSDAY = 5;
public static int FRIDAY = 6;
public static int SATURDAY = 7; /** @serial */
private int day;
/** @serial */
private int month;
/** @serial */
private int year;
}
注意其中的daysBetween()方法。package corejava;import java.util.*;
import java.io.*;/**
Stores dates and perform date arithmetic. This is another date class, but more convenient that
<tt>java.util.Date</tt> or <tt>java.util.Calendar</tt> @version 1.20 5 Oct 1998
@author Cay Horstmann
*/public class Day implements Cloneable, Serializable
{ /**
Constructs today's date
*/
public Day()
{ GregorianCalendar todaysDate
= new GregorianCalendar();
year = todaysDate.get(Calendar.YEAR);
month = todaysDate.get(Calendar.MONTH) + 1;
day = todaysDate.get(Calendar.DAY_OF_MONTH);
} /**
Constructs a specific date @param yyyy year (full year, e.g., 1996,
<i>not</i> starting from 1900)
@param m month
@param d day
@exception IllegalArgumentException if yyyy m d not a
valid date
*/
public Day(int yyyy, int m, int d)
{ year = yyyy;
month = m;
day = d;
if (!isValid())
throw new IllegalArgumentException();
}
/**
Advances this day by n days. For example.
d.advance(30) adds thirdy days to d @param n the number of days by which to change this
day (can be < 0)
*/
public void advance(int n)
{ fromJulian(toJulian() + n);
} /**
Gets the day of the month @return the day of the month (1...31)
*/ public int getDay()
{ return day;
} /**
Gets the month
@return the month (1...12)
*/ public int getMonth() { return month;
} /**
Gets the year
@return the year (counting from 0, <i>not</i> from 1900)
*/ public int getYear()
{ return year;
}
/**
Gets the weekday
@return the weekday ({@link Day#SUNDAY}, ...,
{@link Day#SATURDAY})
*/
public int weekday()
{ return (toJulian() + 1) % 7 + 1;
}
/**
The number of days between this and day parameter
@param b any date
@return the number of days between this and day parameter
and b (> 0 if this day comes after b)
*/
public int daysBetween(Day b)
{ return toJulian() - b.toJulian();
} /**
A string representation of the day
@return a string representation of the day
*/
public String toString()
{ return "Day[" + year + "," + month + "," + day + "]";
} /**
Makes a bitwise copy of a Day object
@return a bitwise copy of a Day object
*/
public Object clone()
{ try
{ return super.clone();
} catch (CloneNotSupportedException e)
{ // this shouldn't happen, since we are Cloneable
return null;
}
} /**
Compares this Day against another object
@param obj another object
@return true if the other object is identical to this Day object
*/ public boolean equals(Object obj)
{ if (!getClass().equals(obj.getClass())) return false;
Day b = (Day)obj;
return day == b.day && month == b.month && year == b.year;
} /**
Computes the number of days between two dates
@return true iff this is a valid date
*/
private boolean isValid()
{ Day t = new Day();
t.fromJulian(this.toJulian());
return t.day == day && t.month == month
&& t.year == year;
} /**
@return The Julian day number that begins at noon of
this day
Positive year signifies A.D., negative year B.C.
Remember that the year after 1 B.C. was 1 A.D. A convenient reference point is that May 23, 1968 noon
is Julian day 2440000. Julian day 0 is a Monday. This algorithm is from Press et al., Numerical Recipes
in C, 2nd ed., Cambridge University Press 1992
*/ private int toJulian()
{ int jy = year;
if (year < 0) jy++;
int jm = month;
if (month > 2) jm++;
else
{ jy--;
jm += 13;
}
int jul = (int) (java.lang.Math.floor(365.25 * jy)
+ java.lang.Math.floor(30.6001*jm) + day + 1720995.0); int IGREG = 15 + 31*(10+12*1582);
// Gregorian Calendar adopted Oct. 15, 1582 if (day + 31 * (month + 12 * year) >= IGREG)
// change over to Gregorian calendar
{ int ja = (int)(0.01 * jy);
jul += 2 - ja + (int)(0.25 * ja);
}
return jul;
} /**
Converts a Julian day to a calendar date This algorithm is from Press et al., Numerical Recipes
in C, 2nd ed., Cambridge University Press 1992
@param j the Julian date
*/ private void fromJulian(int j)
{ int ja = j;
int JGREG = 2299161;
/* the Julian date of the adoption of the Gregorian
calendar
*/ if (j >= JGREG)
/* cross-over to Gregorian Calendar produces this
correction
*/
{ int jalpha = (int)(((float)(j - 1867216) - 0.25)
/ 36524.25);
ja += 1 + jalpha - (int)(0.25 * jalpha);
}
int jb = ja + 1524;
int jc = (int)(6680.0 + ((float)(jb-2439870) - 122.1)
/365.25);
int jd = (int)(365 * jc + (0.25 * jc));
int je = (int)((jb - jd)/30.6001);
day = jb - jd - (int)(30.6001 * je);
month = je - 1;
if (month > 12) month -= 12;
year = jc - 4715;
if (month > 2) --year;
if (year <= 0) --year;
} public static int SUNDAY = 1;
public static int MONDAY = 2;
public static int TUESDAY = 3;
public static int WEDNESDAY = 4;
public static int THURSDAY = 5;
public static int FRIDAY = 6;
public static int SATURDAY = 7; /** @serial */
private int day;
/** @serial */
private int month;
/** @serial */
private int year;
}
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