(Display calendars) Rewrite the PrintCalendar class in Listing 1 to display a calendar for...

(Display calendars) Rewrite the PrintCalendar class in Listing 1 to display a calendar for a specified month using the Calendar and GregorianCalendar classes. Your program receives the month and year from the command line. For example:

java Exercise13_04 5 2016

This displays the calendar shown in Figure 1.

FIGURE 1 The program displays a calendar for May 2016.

You also can run the program without the year. In this case, the year is the current year. If you run the program without specifying a month and a year, the month is the current month.

LISTING 1 PrintCalendar.java

1 import java.util.Scanner;
2
3 public class PrintCalendar {
4 /** Main method */
5 public static void main(String[] args) {
6 Scanner input = new Scanner(System.in);
7
8 // Prompt the user to enter year
9 System.out.print("Enter full year (e.g., 2012): ");
10 int year = input.nextInt();
11
12 // Prompt the user to enter month
13 System.out.print("Enter month as a number between 1 and 12: ");
14 int month = input.nextInt();
15
16 // Print calendar for the month of the year
17 printMonth(year, month);
18 }
19
20 /** Print the calendar for a month in a year */
21 public static void printMonth(int year, int month) {
22 // Print the headings of the calendar
23 printMonthTitle(year, month);
24
25 // Print the body of the calendar
26 printMonthBody(year, month);
27 }
28
29 /** Print the month title, e.g., March 2012 */
30 public static void printMonthTitle(int year, int month) {
31 System.out.println(" " + getMonthName(month)
32 + " " + year);
33 System.out.println("-----------------------------");
34 System.out.println(" Sun Mon Tue Wed Thu Fri Sat");
35 }
36
37 /** Get the English name for the month */
38 public static String getMonthName(int month) {
39 String monthName = "";
40 switch (month) {
41 case 1: monthName = "January"; break;
42 case 2: monthName = "February"; break;
43 case 3: monthName = "March"; break;
44 case 4: monthName = "April"; break;
45 case 5: monthName = "May"; break;
46 case 6: monthName = "June"; break;
47 case 7: monthName = "July"; break;
48 case 8: monthName = "August"; break;
49 case 9: monthName = "September"; break;
50 case 10: monthName = "October"; break;
51 case 11: monthName = "November"; break;
52 case 12: monthName = "December";
53 }
54
55 return monthName;
56 }
57
58 /** Print month body */
59 public static void printMonthBody(int year, int month) {
60 // Get start day of the week for the first date in the month
61 int startDay = getStartDay(year, month)
62
63 // Get number of days in the month
64 int numberOfDaysInMonth = getNumberOfDaysInMonth(year, month);
65
66 // Pad space before the first day of the month
67 int i = 0;
68 for (i = 0; i
69 System.out.print(" ");
70
71 for (i = 1; i <= numberOfDaysInMonth; i++) {
72 System.out.printf("%4d", i);
73
74 if ((i + startDay) % 7 == 0)
75 System.out.println();
76 }
77
78 System.out.println();
79 }
80
81 /** Get the start day of month/1/year */
82 public static int getStartDay(int year, int month) {
83 final int START_DAY_FOR_JAN_1_1800 = 3;
84 // Get total number of days from 1/1/1800 to month/1/year
85 int totalNumberOfDays = getTotalNumberOfDays(year, month);
86
87 // Return the start day for month/1/year
88 return (totalNumberOfDays + START_DAY_FOR_JAN_1_1800) % 7;
89 }
90
91 /** Get the total number of days since January 1, 1800 */
92 public static int getTotalNumberOfDays(int year, int month) {
93 int total = 0;
94
95 // Get the total days from 1800 to 1/1/year
96 for (int i = 1800; i
97 if (isLeapYear(i))
98 total = total + 366;
99 else
100 total = total + 365;
101
102 // Add days from Jan to the month prior to the calendar month
103 for (int i = 1; i
104 total = total + getNumberOfDaysInMonth(year, i);
105
106 return total;
107 }
108
109 /** Get the number of days in a month */
110 public static int getNumberOfDaysInMonth(int year, int month) {
111 if (month == 1 || month == 3 || month == 5 || month == 7 ||
112 month == 8 || month == 10 || month == 12)
113 return 31;
114
115 if (month == 4 || month == 6 || month == 9 || month == 11)
116 return 30;
117
118 if (month == 2) return isLeapYear(year) ? 29 : 28;
119
120 return 0; // If month is incorrect
121 }
122
123 /** Determine if it is a leap year */
124 public static boolean isLeapYear(int year) {
125 return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
126 }
127 }