Question

Create a class called Date212 to represent a date. It will store the year, month and day as integers (not as a String in the form yyyymmdd (such as 20161001 for October 1, 2016), so you will need three private instance variables. Two constructors should be provided, one that takes three integer parameters, and one that takes a String.

The constructor with the String parameter and should validate the parameter. As you are reading the dates you should check that the value read in is legal (8 digits), and if it is not, print it to the console and do not put it in the array of dates., and then use the substring method of class String to pull out the month, day and year, parse them as integers and call the three-argument constructor.

The three-argument constructor should make sure that the month and day values are legal. To call another constructor from within a constructor, use the method this :

public Date212 (String d) { // the one-argument constructor

… this(year, month, day) // invokes the three-argument constructor.

…

}

The dates will be taken from an .txt input file in the format :

20161001

20080912,20131120,19980927

20020202

20120104

ToString() for Class Date212. Create a toString method in class Date212 the will return the date in the form mm/dd/yyyy. Use this method to display the dates in DateGUI.

Answer 1

Java Program:

/* Java Program that reads date string from file and prints in the specified format */

import java.util.*;
import java.io.*;

//Class that holds date
class Date212
{
   //Private member variables
   private int year;
   private int month;
   private int day;
  
   //Three argument Constructor
   public Date212 (int y, int m, int d)
   {
       //Validating month
       if(m < 1 || m > 12)
           System.out.println("\n Invalid month... \n");
          
       //Validating day  
       else if(d < 1 || d > 31)
           System.out.println("\n Invalid day... \n");
       else
       {
           //Assigning values to member variables
           this.year = y;
           this.month = m;
           this.day = d;
       }
   }
  
   //Constructor with single argument
   public Date212 (String d)
   {
       //Calling three argument constructor
       this(Integer.parseInt(d.substring(0, 4)), Integer.parseInt(d.substring(4, 6)), Integer.parseInt(d.substring(6, 8)));
   }
  
   //Method that returns date in the required format
   public String toString()
   {
       return String.format("%02d", month) + "/" + String.format("%02d", day) + "/" + String.format("%04d", year);
   }
}

//Class that test Date212 class
class Date212Driver
{
   //Main program
   public static void main(String args[])
   {
       //Array list to hold list of dates
       ArrayList<Date212> dates = new ArrayList<Date212>();
      
       //Opening file
       File file = new File("birthDates.txt");
      
       try
       {
           Scanner sc = new Scanner(file);
      
           //Reading date from file
           while (sc.hasNextLine())
           {
               //Reading a line
               String temp = sc.nextLine();
              
               //Validating length
               if(temp.length() == 8)
               {
                   //Creating an object
                   Date212 tdate = new Date212(temp);
                  
                   //Adding to array list
                   dates.add(tdate);
               }
           }
          
           sc.close();
       }
       catch (FileNotFoundException e)
       {
           //Handling exceptions
           e.printStackTrace();
       }
      
       //Printing values in array list
       for(int i=0; i<dates.size(); i++)
           System.out.println("\n Date: " + dates.get(i) + " \n");
   }
}

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Sample Output:

CWindowslsystem32\cmd.exe D:Java>javac Date212Driver.java D:\Java java Date212Driver C: Date: 10/01/2016 Date: 09/12/2008 Date: 02/02/2002 Date: 01/04/2012 Date: 11/20/2013 Date: 09/27/1998 D:Java>