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
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
/**
* Assignment 2, COMP268 Class: WeekDay.java
*
* @description A class used to determine the week day for any given date.
* @author: mo khan Student ID: 3431709
* @date Jul 13, 2019
* @version 1.0
*/
package Q6;
import java.util.*;
public class WeekDay {
private static final String[] DAYS =
new String[] {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
private static final int[] MONTHS = new int[] {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
/**
* Returns the day of the week that a certain date falls on.
*
* @param day the day of the month
* @param month the month of the year
* @param year the year
* @return the name of the day of the week. (Sunday to Saturday)
*/
public String getWeekDay(int day, int month, int year) {
this.ensureValidDate(year, month, day);
return DAYS[daysSinceEpoch(day, month, year) % 7];
}
private int daysSinceEpoch(int day, int month, int year) {
int days = ((year - 1900) * 365) + ((year - 1900) / 4);
if (isLeapYear(year) && (month == 1 || month == 2)) days -= 1;
days += daysThisYearUpTo(day, month);
return days;
}
private boolean isLeapYear(int year) {
return year % 4 == 0;
}
private int daysThisYearUpTo(int day, int month) {
int days = 0;
for (int i = 1; i < month; i++) days += daysInMonth(i);
return days + day;
}
private int daysInMonth(int month) {
return MONTHS[month - 1];
}
private void ensureValidDate(int year, int month, int day) {
if (month < 1 || month > 12 || day < 1 || day > MONTHS[month - 1])
throw new IllegalArgumentException();
}
/**
* The entry point to the console application.
* @param args the argument vector given to the program.
* */
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.println("--- Question 6 ---");
System.out.println("Enter year:");
int year = in.nextInt();
if (year < 1900 || year > 2100) {
System.out.println("Invalid year.");
System.exit(-1);
}
System.out.println("Enter month:");
int month = in.nextInt();
if (month < 1 || month > 12 || (year == 1900 && month < 3) || (year == 2100 && month > 2)) {
System.out.println("Invalid month.");
System.exit(-1);
}
System.out.println("Enter day:");
int day = in.nextInt();
System.out.println();
System.out.println("Today is:");
try {
System.out.println(new WeekDay().getWeekDay(day, month, year));
} catch (IllegalArgumentException error) {
System.out.println("Invalid date.");
System.exit(-1);
}
System.out.println();
}
}
|
