Question

Create a simple Java class for a Month object with the following requirements:

 This program will have a header block comment with your name, the course and section, as well as a brief description of what the class does.
 All methods will have comments concerning their purpose, their inputs, and their outputs
 One integer property: monthNumber (protected to only allow values 1-12). This is a numeric representation of the month (e.g. 1 represents January, 2 represents February, etc.)
 A constructor that takes no arguments, and sets the monthNumber to 1.
 Add a second constructor that takes in an integer argument to set the initial monthNumber for the new Month object. Use data protection to prevent the user from entering a number less than 1 or greater than 12. When a non-valid input is entered, throw a new IllegalArgumentException.
 A setMonth() method that takes an integer and uses data protection to prevent the user from entering a number less than 1 or greater than 12. Also throw an IllegalArgumentException if an illegal value is entered.
 A getMonth() method that returns the monthNumber as an integer.
 Add a String array property that holds the values of the month names (e.g. monthNames[3] would hold the value “March”). Remember, you can leave the 0th index blank/null
 Add a toString() method to use the monthNumber property to return the name of the month as a String. Use the private global String array with the names of the months in it to return the proper String based on the monthNumber.
 Add an equals() method that takes in a month object and returns a boolean based on the values of each object’s monthNumber
 Add a compareTo() method that takes in a month object and returns a negative number if the called object is smaller than the passed in object, a positive number if the called object is bigger than the passed in object, and zero (0) if the two objects are equivalent.

Create a simple program using Java that demonstrates the month object with the following requirements:

 That creates a month object using the no argument constructor.
 A second month object is created using the constructor that takes in an integer argument.
 Additionally, use either a do or while loop to get the user to enter a number between 1 and 12 using the setMonth() method on the 1st month object. The loop will continue until they enter a valid number.
 The program will display the month number for both of the objects using the getMonth() method.
 Display the month names using toString() for the months created, and see whether they are the same or not.
 Additionally, use the equals() method created above to show whether the two months are equivalent to each other or not.
 Use the compareTo() method created above to show which object is the biggest.
 Use appropriate try and catch statements to properly handle erroneous input by the user.

Answer 1

/* The java program that demonstrates the methods
* of Month class. Then print the results of the program
* on console output.
* */
//MonthTester.java
import java.util.Scanner;
public class MonthTester
{
   public static void main(String[] args)
   {
       Scanner console=new Scanner(System.in);
       //default constructor object
       Month one=new Month();
       //second Month object with month number =1
       Month second=new Month(1);
       //declare month variable
       int month = 0;
       //do-while loop
       do
       {      
           //try-catch block to handle invalid input
           try
           {
               System.out.printf("Enter month number : ");
               month=Integer.parseInt(console.nextLine());
              
               if(month<1 || month>12)
                   System.out.println("Invalid month number");
               else
                   second.setMonth(month);          
           }
           catch (Exception e)
           {
               System.out.println("invalid input");
           }

       }while(month<1 ||month>12);

       //print one and second objects
       System.out.println("Default month object");
       System.out.println(one.toString());
       System.out.println("Second month object");
       System.out.println(second.toString());

       //checking if equal method one two objects
       if(one.equals(second))
           System.out.println(one+" and "+second+" are same objects");
       else
           System.out.println(one+" and "+second+" are not same objects");
      
       //calling compareTo method on two month objects
       if(second.compareTo(one)>0)
           System.out.println(second+" is more than "+one);
       else if(second.compareTo(one)<0)
           System.out.println(second+" is less than "+one);
       else
           System.out.println(second+" and "+one+" are same objects");

   }
}
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/** The month class has an instance variable monthNumber
* The constructor and parameterized constructor is to set
* the default and parameter values to the month class.
* The class has setter and getter method for instance variable,
* monthNumber.
* */
//Month.java
public class Month implements Comparable
{
   //declare an instance variable
   private int monthNumber;
   //declare an array of month names
   private String months[]= {"", "January","February","March","April","May","June","July",
           "August","September","October","November","December"};
  
   //default constructor
   public Month()
   {
       monthNumber=1;
   }
   //parameter constructor
   public Month(int month)
   {
       if(month<1 || month>12)
           monthNumber=1;
       else
           monthNumber=month;
   }
  
   //settter method for month
   public void setMonth(int month)
   {
       if(month<1 || month>12)
           monthNumber=1;
       else
           monthNumber=month;
   }
   //getter method for month
   public int getMonth()
   {
       return monthNumber;
   }
   /*Override the toString method*/
   public String toString()
   {
       return String.format("Month Name: %s", months[monthNumber]);
   }
   /*Override the equals method*/
   public boolean equals(Object obj)
   {
       Month other=(Month)obj;
       return monthNumber==other.getMonth();
   }
   /*Override the compareTo method*/
   public int compareTo(Object obj)
   {
       Month other=(Month)obj;
       return monthNumber-other.getMonth();
   }
}

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Sample Output:

RUn1:

Enter month number : 3
Default month object
Month Name: January
Second month object
Month Name: March
Month Name: January and Month Name: March are not same objects
Month Name: March is more than Month Name: January

Run2:

Enter month number : 1
Default month object
Month Name: January
Second month object
Month Name: January
Month Name: January and Month Name: January are same objects
Month Name: January and Month Name: January are same objects