Printing the month name for the month number

Question

This program asks a user to input any number equal to or between 1-12. It then converts the number to a message that will be printed (Copy the program to see it yourself). Is there a way to make the code shorter by still using the switch statement?

This is homework, so using a switch is a requirement.

import javax.swing.JOptionPane;

public class NumOfMonth {

   public static void main(String[] args) {

    int num = Integer.parseInt (JOptionPane.showInputDialog ("Enter any number equal to or between 1-12 to display the month"));

    switch (num)
    {
    case 1:
        System.out.println ("The name of month number 1 is January");
        break;
    case 2:
        System.out.println ("The name of month number 2 is February");
        break;
    case 3:
        System.out.println ("The name of month number 3 is March");
        break;
    case 4:
        System.out.println ("The name of month number 4 is April");
        break;
    case 5:
        System.out.println ("The name of month number 5 is May");
        break;
    case 6:
        System.out.println ("The name of month number 6 is June");
        break;
    case 7:
        System.out.println ("The name of month number 7 is July");
        break;
    case 8:
        System.out.println ("The name of month number 8 is August");
        break;
    case 9:
        System.out.println ("The name of month number 9 is September");
        break;
    case 10:
        System.out.println ("The name of month number 10 is October");
        break;
    case 11:
        System.out.println ("The name of month number 11 is November");
        break;
    case 12:
        System.out.println ("The name of month number 12 is December");
        break;
        default:
            System.out.println ("You have entered an invalid number");
        }
    } // main method
}

Answer 1

As you have probably noticed, there is a lot of repetition which we can take advantage of. We can declare an array containing all the string representations of the months like so.

String[] months = {"January", "February", "March", ..., "December"};

Once you have that, we can simply do:

if (num >= 1 && num <= 12) {
    System.out.format("The name of month number %d is %s\n", num, months[num-1]);
} else {
    System.out.println("You have entered an invalid number");
}

Edit: sorry, just saw the bit about "by still using the switch statement". I'll still leave this here though because I think it's a better solution than a switch statement.

If you really insist on using the switch (but you shouldn't), then you can at least extract the repeated string part and formatting logic to a helper method:

private static void printMonth(int num, String name) {
    System.out.printf("The name of month number %d is %s%n", num, name);
}

And then rewrite the switch using that method:

switch (num)
{
case 1:
    printMonth(num, "January");
    break;
case 2:
    printMonth(num, "February");
    break;
// .... and so on

But really, insisting on a switch here is forced, and goes against good practices.

Answer 2

Month enum:

You could simply use the Month enum. This enum is defined as part of the new java.time framework built into Java 8 and later.

You can use this to easily get the name of the month:

int monthNumber = 5;
Month.of(monthNumber).name();

Output will be:

MAY

Answer 3

First of all I would add a loop around the input to make sure that a proper month number is entered. This could also be extended with exception handling if that has been covered, as the user might input text.

int monthNumber = 0;
while (true) {
    monthNumber = Integer.parseInt (JOptionPane.showInputDialog ("Enter any number equal to or between 1-12 to display the month"));

    if (monthNumber < 1) && (monthNumber > 12) {
        System.out.println("You have entered an invalid month number");
    } else {
        break; // Number is a valid month number
    }
}

Secondly, my take on converting the monthNumber into a name when being constrained to using a switch would be something like the following:

switch(monthNumber): {
  case  1: monthName = 'January'; break;
  case  2: monthName = 'February'; break;
  ...
  case 12: monthName = 'December'; break;
}

System.out.printf("The name of month number %d is %s\n", monthNumber, monthName);

This way the code is concise and precise. The error handling is close to the actual input, and the "business logic" is tightly coupled in the switch, before a final presentation statement at the end.