第六章第三十四题（打印日历）(Print calendar)
**6.34（打印日历）编程练习题3.21使用Zeller一致性原理来计算某天是星期几。使用Zeller的算法简化程序清单6-12以获得每月开始的第一天是星期几。 **6.34(Print calendar) Programming Exercise 3.21 uses Zeller’s congruence to calculate the day of the week. Simplify Listing 6.12, PrintCalendar.java, using Zeller’s algorithm to get the start day of the month.参考代码：
package chapter06
;
import java
.util
.Scanner
;
public class Code_34 {
public static void main(String
[] args
) {
Scanner input
= new Scanner(System
.in
);
System
.out
.print("Enter full year (e.g., 2012): ");
int year
= input
.nextInt();
System
.out
.print("Enter month as a number between 1 and 12: ");
int month
= input
.nextInt();
printMonth(year
, month
);
}
public static void printMonth(int year
, int month
) {
printMonthTitle(year
, month
);
printMonthBody(year
, month
);
}
public static void printMonthTitle(int year
, int month
) {
System
.out
.println(" " + getMonthName(month
) + " " + year
);
System
.out
.println("-----------------------------");
System
.out
.println(" Sun Mon Tue Wed Thu Fri Sat");
}
public static String
getMonthName(int month
) {
String monthName
= "";
switch (month
) {
case 1:
monthName
= "January";
break;
case 2:
monthName
= "February";
break;
case 3:
monthName
= "March";
break;
case 4:
monthName
= "April";
break;
case 5:
monthName
= "May";
break;
case 6:
monthName
= "June";
break;
case 7:
monthName
= "July";
break;
case 8:
monthName
= "August";
break;
case 9:
monthName
= "September";
break;
case 10:
monthName
= "October";
break;
case 11:
monthName
= "November";
break;
case 12:
monthName
= "December";
}
return monthName
;
}
public static void printMonthBody(int year
, int month
) {
int startDay
= getStartDay(year
, month
);
int numberOfDaysInMonth
= getNumberOfDaysInMonth(year
, month
);
int i
= 0;
for (i
= 0; i
< startDay
; i
++)
System
.out
.print(" ");
for (i
= 1; i
<= numberOfDaysInMonth
; i
++) {
System
.out
.printf("%4d", i
);
if ((i
+ startDay
) % 7 == 0)
System
.out
.println();
}
System
.out
.println();
}
public static int getStartDay(int year
, int month
) {
int day
= 1, h
, q
, m
, j
, k
,statement
;
q
= day
;
if(month
== 1 || month
== 2) {
month
+= 12;
year
-= 1;
}
m
= month
;
j
= year
/ 100;
k
= year
% 100;
h
= (q
+ (26 * (m
+ 1) / 10) + k
+ k
/ 4 + j
/ 4 + 5 * j
) % 7;
switch(h
) {
case 0:
statement
= 6; break;
case 1:
statement
= 0; break;
case 2:
statement
= 1; break;
case 3:
statement
= 2; break;
case 4:
statement
= 3; break;
case 5:
statement
= 4; break;
case 6:
statement
= 5; break;
default:
statement
= -1;
}
return statement
;
}
public static int getNumberOfDaysInMonth(int year
, int month
) {
if (month
== 1 || month
== 3 || month
== 5 || month
== 7 || month
== 8 || month
== 10 || month
== 12)
return 31;
if (month
== 4 || month
== 6 || month
== 9 || month
== 11)
return 30;
if (month
== 2)
return isLeapYear(year
) ? 29 : 28;
return 0;
}
public static boolean isLeapYear(int year
) {
return year
% 400 == 0 || (year
% 4 == 0 && year
% 100 != 0);
}
}
结果显示：
Enter full year
(e
.g
., 2012): 2012
Enter month as a number between
1 and
12: 2
February
2012
-----------------------------
Sun Mon Tue Wed Thu Fri Sat
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29
Process finished with exit code
0
