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《JAVA核心技术》范例中的问题请教
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本文导语: 编译I/O程序:ObjectFileTest.java等程序时一直出现好几个如下错误: D:corejavav1ch12ObjectFileTestObjectFileTest.java:44: 不能解析符号 符号:类 Day 位置:类 in Employee { public Employee(String n, double s, Day d) ...
编译I/O程序:ObjectFileTest.java等程序时一直出现好几个如下错误:
D:corejavav1ch12ObjectFileTestObjectFileTest.java:44: 不能解析符号
符号:类 Day
位置:类 in Employee
{ public Employee(String n, double s, Day d)
^
是何原因呢?给20分。
D:corejavav1ch12ObjectFileTestObjectFileTest.java:44: 不能解析符号
符号:类 Day
位置:类 in Employee
{ public Employee(String n, double s, Day d)
^
是何原因呢?给20分。
|
呵呵,是这样的。carejava的作者写了几个类。放在carejava包里。你得import它,然后才能用。
或者,把下面的程序放到你当前类的子目录里:
import java.util.*;
import java.io.*;
/**
Stores dates and perform date arithmetic.
This is another date class, but more convenient that
java.util.Date or java.util.Calendar
@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,
not 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 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 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
或者,把下面的程序放到你当前类的子目录里:
import java.util.*;
import java.io.*;
/**
Stores dates and perform date arithmetic.
This is another date class, but more convenient that
java.util.Date or java.util.Calendar
@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,
not 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 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 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