Hello. My program seems to be a couple of days off. For example, for January 201
ID: 3888956 • Letter: H
Question
Hello. My program seems to be a couple of days off. For example, for January 2017, should start on a Saturday. It is showing up as starting on Thursday. March 2017 should start on a Wednesday. It is showing up as starting on a Saturday. Any advice/critiques?
package javaCalendar.java;
import java.util.Scanner;
public class javaCalendar {
public static void main ( String args []) {
Scanner input = new Scanner(System.in);
//print the year
System.out.println("Input the Year (Ex: 2017): ");
int y = input.nextInt();
//print the month
System.out.println("Input the Month (1-12): ");
int m = input.nextInt();
//ask method to display calendar for month of year
printMonth(y, m);
}
//method to display Header for Month
public static void printMonthHeader (int y, int m) {
System.out.println(" " + getMonthName (m) + " " + y);
System.out.println("_____________________________");
System.out.println(" Sun Mon Tue Wed Thu Fri Sat");
}
//method to display calendar for a month in a particular year
static void printMonth (int y, int m) {
printMonthHeader(y, m);
printMonthBody (y,m);
}
static String getMonthName (int m)
{
String monthName = null;
switch (m) {
case 1: monthName = "January";
case 2: monthName = "February";
case 3: monthName = "March";
case 4: monthName = "April";
case 5: monthName = "May";
case 6: monthName = "June";
case 7: monthName = "July";
case 8: monthName = "August";
case 9: monthName = "September";
case 10: monthName = "October";
case 11: monthName = "November";
case 12: monthName = "December";
}
return monthName;
}
static void printMonthBody(int y, int m) {
int dayNumb = getStartDay(y, m);
int numberOfDaysInMonth = getNumberOfDaysInMonth(y,m);
int i = 0;
for (i = 0; i <dayNumb; i++)
System.out.print(" ");
for (i = 1; i <= numberOfDaysInMonth; i++) {
if (i<10)
System.out.print(" " + i);
else System.out.print (" " + i);
if ((i + dayNumb) % 7 == 0)
System.out.println();
}
System.out.println();
}
static int getStartDay (int y, int m) {
return getDayOfWeek (y, m, 1);
}
public static int getDayOfWeek( int m, int d, int y )
{
// Adjust month number & year to fit Zeller's numbering system
if (m < 3)
{
m = m + 12;
y = y - 1;
}
int k = y % 100; // Calculate year within century
int j = y / 100; // Calculate century term
int h = 0; // Day number of first day in month 'm'
h = ( d + ( 13 * ( m + 1 ) / 5 ) + k + ( k / 4 ) + ( j / 4 ) +
( 5 * j ) ) % 7;
// Convert Zeller's value to ISO value (1 = Mon, ... , 7 = Sun )
int dayNum = ( ( h + 5 ) % 7 ) + 1;
return dayNum;
}
public static int getNumberOfDaysInMonth (int y, int m)
{
if (m == 1 || m == 3 || m == 5 || m ==7 || m == 8 || m == 10 || m == 12)
return 31;
if (m == 4 || m == 6 || m == 9 || m == 11)
return 30;
if (m == 2) return isLeapYear (y) ?29:28;
return 0;
}
static boolean isLeapYear (int y)
{
return y % 400 == 0 || (y % 4 ==0 && y % 100 != 0);
}
}
Explanation / Answer
1. change your code
public static int getDayOfWeek( int m, int d, int y )
to
public static int getDayOfWeek( int y, int m, int d )
Also, put a break; statement after every case statement
case 1: monthName = "January";
case 2: monthName = "February";
case 3: monthName = "March";
case 4: monthName = "April";
case 5: monthName = "May";
case 6: monthName = "June";
case 7: monthName = "July";
case 8: monthName = "August";
case 9: monthName = "September";
case 10: monthName = "October";
case 11: monthName = "November";
case 12: monthName = "December";
to
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";
break;
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