Days In A Month
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ProblemWrite a Java program DaysInAMonth, that prompts for a month and year and determines the amount of days that will be in the month.
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...By Students"I remember coming into COMP 1010 having taken AP Computer Science in high school. One thing to note is the KISS theory, Keep it Simple Stupid. In other words, don't over complicate the matter where even yourself can't understand your own code looking over it.
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SolutionStart by importing the swing java package. import javax.swing.*; import java.util.Scanner;
final static int MONTH30 = 30; final static int FEB = 28; final static int MONTH31 = 31;
int year, monthNum; String monthName; Scanner input = new Scanner(System.in); //sentinel values for error checking monthNum = -1; year = -1; monthName = "";
System.out.print("Please enter the month [Jan(1) to Dec(12)]: ");
if(input.hasNextInt())
{
monthNum = input.nextInt();
System.out.print("Please enter the Year: ");
if(input.hasNextInt())
{
//code here
}
else
{
System.out.println("Please try again, there was an error with the month or the year you have entered");
}
}
else
{
System.out.println("Invalid month number entered, choose between 1 - 12 (Jan - Dec)");
}
Please enter the month [Jan(1) to Dec(12)]: abcd Please enter the Year: 2009 Invalid input of month Please enter the month [Jan(1) to Dec(12)]: 12 Please enter the Year: asdf Invalid Input of Year
First case, if user left both month and year blank. if (monthNum <= 0 && year <= 999)
System.out.println("Please try again, there was an error with the month and the year you have entered");
Please enter the month [Jan(1) to Dec(12)]: -1 Please enter the Year: 987 Please try again, there was an error with the month and the year you have entered
else if (monthNum <= 0)
{
System.out.println("Please try again, there was an error with the month you have entered");
}
Please enter the month [Jan(1) to Dec(12)]: -1 Please enter the Year: 2009 Please try again, there was an error with the month you have entered
else if (year <= 999)
{
System.out.println("Please try again, there was an error with the month you have entered");
}
Please enter the month [Jan(1) to Dec(12)]: 12 Please enter the Year: 987 Please try again, there was an error with the month you have entered
The last case, which is most important since it is processing the valid input will be the next step. In this case there is a set of nested cases. Again, we will have to separate the conditions into statements. In this problem we separated the months by 31 days, 30 days, and February as a case of its own for calculating leap years. Months with 31 days, since we are assuming Jan = 0, the condition will "or" all integer representations of the months with 31 days. Remember July and August are back to back months with 31 days! The first condition checks for the appropriate monthNum and the nested conditions will assign the appropriate monthName depending on which integer was chosen. There may be alternate solutions and methods to solve this problem but for the sake of example and topics to cover we have chosen this method. Lastly, System.out.println prints an meaningful output message. //JAN //MAR //MAY //JUL //AUG //OCT //DEC
if (monthNum == 1 || monthNum == 3 || monthNum == 5 ||
monthNum == 7 || monthNum == 8 || monthNum == 10 ||
monthNum == 12)
{
if (monthNum == 1)
monthName = "January";
else if (monthNum == 3)
monthName = "March";
else if (monthNum == 5)
monthName = "May";
else if (monthNum == 7)
monthName = "July";
else if (monthNum == 8)
monthName = "August";
else if (monthNum == 10)
monthName = "October";
else if (monthNum == 12)
monthName = "December";
System.out.println(monthName + " " + year + " has " + MONTH31 + " days.");
}
Please enter the month [Jan(1) to Dec(12)]: 3 Please enter the Year: 2009 March 2009 has 31 days.
//FEB
else if (monthNum == 2)
{
monthName = "February";
//check for leap
if (year % 4 == 0)
System.out.println(monthName + " " + year + " has " + (FEB + 1) + " days.");
else
System.out.println(monthName + " " + year + " has " + FEB + " days.");
}
Please enter the month [Jan(1) to Dec(12)]: 2 Please enter the Year: 2008 February 2009 has 29 days. Please enter the month [Jan(1) to Dec(12)]: 2 Please enter the Year: 2009 February 2009 has 28 days.
//APR //JUN //SEP //NOV
else if (monthNum == 4|| monthNum == 6 || monthNum == 9 || monthNum == 11)
{
if (monthNum == 4)
monthName = "April";
else if (monthNum == 6)
monthName = "June";
else if (monthNum == 9)
monthName = "September";
else if (monthNum == 11)
monthName = "November";
System.out.println(monthName + " " + year + " has " + MONTH30 + " days.");
}
Please enter the month [Jan(1) to Dec(12)]: 11 Please enter the Year: 2009 November 2009 has 30 days.
Lastly, for additional robustness, you can check if the user enters a monthNum that is too high. Remember, initially we checked for negative monthNum, but this time is now the opposite end of the spectrum where the monthNum is too beyond the scope. If the monthNum is too high output a meaningful error message. //number is larger than 11
else
System.out.println("Invalid month number entered, choose between 1 - 12 (Jan - Dec)");
Please enter the month [Jan(1) to Dec(12)]: 13 Please enter the Year: 2009 Invalid month number entered, choose between 1 - 12 (Jan - Dec)
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