Lab 12-12-2005 (1) Constructor

檔案 ConstructorsDemo
package aaa;

public class ConstructorsDemo
{
public static void main(String[] args)
{
Date date1 = new Date("December", 16, 1770);
Date date2 = new Date(12, 27, 1756);
Date date3 = new Date(1882);
Date date4 = new Date( );

System.out.println("Whose birthday is " + date1 + "?");
System.out.println("Whose birthday is " + date2 + "?");
System.out.println("Whose birthday is " + date3 + "?");
System.out.println("The default date is " + date4 + ".");
}
}

檔案 Date

package aaa;
import java.io.*;
public class Date
{
private String month;
private int day;
private int year;

public Date( )
{
month = "January";
day = 1;
year = 1000;
}

public Date(int monthInt, int day, int year)
{
setDate(monthInt, day, year);
}

public Date(String monthString, int day, int year)
{
setDate(monthString, day, year);
}

public Date(int year)
{
setDate(1, 1, year);
}

public Date(Date aDate)
{
if (aDate == null)
{
System.out.println("Fatal Error.");
System.exit(0);
}

month = aDate.month;
day = aDate.day;
year = aDate.year;
}

public void setDate(int monthInt, int day, int year)
{
if (dateOK(monthInt, day, year))
{
this.month = monthString(monthInt);
this.day = day;
this.year = year;
}
else
{
System.out.println("Fatal Error");
System.exit(0);
}
}

public void setDate(String monthString, int day, int year)
{
if (dateOK(monthString, day, year))
{
this.month = monthString;
this.day = day;
this.year = year;
}
else
{
System.out.println("Fatal Error");
System.exit(0);
}
}

public void setDate(int year)
{
setDate(1, 1, year);
}

public void setYear(int year)
{
if ( (year < 1000) || (year > 9999) )
{
System.out.println("Fatal Error");
System.exit(0);
}
else
this.year = year;
}
public void setMonth(int monthNumber)
{
if ((monthNumber <= 0) || (monthNumber > 12))
{
System.out.println("Fatal Error");
System.exit(0);
}
else
month = monthString(monthNumber);
}

public void setDay(int day)
{
if ((day <= 0) || (day > 31))
{
System.out.println("Fatal Error");
System.exit(0);
}
else
this.day = day;
}

public int getMonth( )
{
if (month.equals("January"))
return 1;
else if (month.equals("February"))
return 2;
else if (month.equalsIgnoreCase("March"))
return 3;
else if (month.equalsIgnoreCase("April"))
return 4;
else if (month.equalsIgnoreCase("May"))
return 5;
else if (month.equals("June"))
return 6;
else if (month.equalsIgnoreCase("July"))
return 7;
else if (month.equalsIgnoreCase("August"))
return 8;
else if (month.equalsIgnoreCase("September"))
return 9;
else if (month.equalsIgnoreCase("October"))
return 10;
else if (month.equals("November"))
return 11;
else if (month.equals("December"))
return 12;
else
{
System.out.println("Fatal Error");
System.exit(0);
return 0;
}
}

public int getDay( )
{
return day;
}

public int getYear( )
{
return year;
}

public String toString( )
{
return (month + " " + day + ", " + year);
}

public boolean equals(Date otherDate)
{
return ( (month.equals(otherDate.month))
&& (day == otherDate.day) && (year == otherDate.year) );
}

public boolean precedes(Date otherDate)
{
return ( (year < otherDate.year) ||
(year == otherDate.year && getMonth( ) < otherDate.getMonth( )) ||
(year == otherDate.year && month.equals(otherDate.month)
&& day < otherDate.day) );
}

public void readInput( ) throws IOException
{
boolean tryAgain = true;
BufferedReader keyboard= new BufferedReader(new InputStreamReader(System.in));

while (tryAgain)
{
System.out.println("Enter month, day, and year.");
System.out.println("Do not use a comma.");
String monthInput = keyboard.readLine( );
int dayInput = keyboard.read( );
int yearInput = keyboard.read( );
if (dateOK(monthInput, dayInput, yearInput) )
{
setDate(monthInput, dayInput, yearInput);
tryAgain = false;
}
else
System.out.println("Illegal date. Reenter input.");
}
}

private boolean dateOK(int monthInt, int dayInt, int yearInt)
{
return ( (monthInt >= 1) && (monthInt <= 12) &&
(dayInt >= 1) && (dayInt <= 31) &&
(yearInt >= 1000) && (yearInt <= 9999) );
}

private boolean dateOK(String monthString, int dayInt, int yearInt)
{
return ( monthOK(monthString) &&
(dayInt >= 1) && (dayInt <= 31) &&
(yearInt >= 1000) && (yearInt <= 9999) );
}

private boolean monthOK(String month)
{
return (month.equals("January") || month.equals("February") ||
month.equals("March") || month.equals("April") ||
month.equals("May") || month.equals("June") ||
month.equals("July") || month.equals("August") ||
month.equals("September") || month.equals("October") ||
month.equals("November") || month.equals("December") );
}

private String monthString(int monthNumber)
{
switch (monthNumber)
{
case 1:
return "January";
case 2:
return "February";
case 3:
return "March";
case 4:
return "April";
case 5:
return "May";
case 6:
return "June";
case 7:
return "July";
case 8:
return "August";
case 9:
return "September";
case 10:
return "October";
case 11:
return "November";
case 12:
return "December";
default:
System.out.println("Fatal Error");
System.exit(0);
return "Error";
}
}
}

圖