Question

Your task is to open a file containing a list of dates in various formats, read each date, determine if it is a valid format and print it in **ISO 8601 format**(YYYY/MM/DD) to console. The list will be terminated by a `-1`.

There are **two** valid formats:
- plain-language format: <Month> <Day>, <Year> where Day and Year are valid integers. ex. `March 3, 1990`.
- reversed ISO format, `DD/MM/YYYY` (Note that we aren't concerned with the precise ordering of month and day; the format is valid if it is 3 valid integers in `N/N/N` format, with the year (the largest number) at the end).
All other date formats should be ignored.

When a valid date is detected print, a String of the date converted into `YYYY/MM/DD` format. For the above example, `March 3, 1990` gets converted to `1990/03/03`. The string `03/03/1990` would likewise get reversed to `1990/03/03`.

Note that the day and month integers need to be left-padded with zeros to two places if not already double-digit, ie. '1' becomes '01' and so on. The `printDateISOFormat()` function created for you will need to be updated to do this.

You do not need to submit a class with a main method for the lab as the autograder has that already. However, it might be easiest for you to test this lab in your own environment.    Our class with the main method looks like this:

import java.io.FileNotFoundException;
import java.io.IOException;

public class RunMe {
    
    public static void main(String[] args) throws IOException, FileNotFoundException {
        DateParser parser = new DateParser();
        parser.readFile();       
    }
}

Here are some examples of possible input to your parser:

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;

public class DateParser {
    // Converts a month name to an integer format
    public static int getMonthAsInt(String monthString) {
        int monthInt;

        // Java switch/case statement
        switch (monthString) {
            case "January":
                monthInt = 1;
                break;
            case "February":
                monthInt = 2;
                break;
            case "March":
                monthInt = 3;
                break;
            case "April":
                monthInt = 4;
                break;
            case "May":
                monthInt = 5;
                break;
            case "June":
                monthInt = 6;
                break;
            case "July":
                monthInt = 7;
                break;
            case "August":
                monthInt = 8;
                break;
            case "September":
                monthInt = 9;
                break;
            case "October":
                monthInt = 10;
                break;
            case "November":
                monthInt = 11;
                break;
            case "December":
                monthInt = 12;
                break;
            default:
                monthInt = 00;
        }

        return monthInt;
    }

    // Prints the given numeric information in ISO 8601 YYYY/MM/DD format.
    public static void printDateISOFormat(int inputYear, int inputMonth, int inputDay) {
        // TODO: modify so that days and months that are single-digit are left-padded
        // with zeros to two digits (ie. '9' becomes '09', '12' stays as '12', etc.)
        System.out.println(inputYear + "/" + month + "/" + day);
    }


    /** Check that the input has the correct numeric data already(yyyy, mm, dd)
    *   but in reversed order (dd/mm/yyyy)
    *   The year will never be smaller than the month or day
    */
    public static boolean validateReverseOrder(String input) {

        return true;
    } 



    /** Valid English format is <Month> <Day>, <Year>
    *   all other formats (besides the reversed order above) 
    *   are considered invalid
    *   For students to complete
    */
    public static boolean validateFormat(String[] input) {

        return true;
    }

    /** For students to complete
    *   Prompts the user for a filename, opens said file, reads in dates and 
    *   converts the valid ones to ISO 8601 (YYYY/MM/DD) format
    *   call printDateISOFormat() to print dates to console
    */
    public void readFile() throws IOException, FileNotFoundException {
        Scanner scnr = new Scanner(System.in);
        String filename = scnr.nextLine().trim();  //use trim() here or you'll have a newline on your filename
        
    }

}

Answer 1

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class DateParser {
// Converts a month name to an integer format
public static int getMonthAsInt(String monthString) {
int monthInt;

// Java switch/case statement
switch (monthString) {
case "January":
monthInt = 1;
break;
case "February":
monthInt = 2;
break;
case "March":
monthInt = 3;
break;
case "April":
monthInt = 4;
break;
case "May":
monthInt = 5;
break;
case "June":
monthInt = 6;
break;
case "July":
monthInt = 7;
break;
case "August":
monthInt = 8;
break;
case "September":
monthInt = 9;
break;
case "October":
monthInt = 10;
break;
case "November":
monthInt = 11;
break;
case "December":
monthInt = 12;
break;
default:
monthInt = 00;
}

return monthInt;
}

// Prints the given numeric information in ISO 8601 YYYY/MM/DD format.
public static void printDateISOFormat(int inputYear, int inputMonth, int inputDay) {
// TODO: modify so that days and months that are single-digit are left-padded
// with zeros to two digits (ie. '9' becomes '09', '12' stays as '12', etc.)
   String day="",month="";
   if(inputDay<10)
       day="0"+inputDay+"";
   if(inputMonth<10)
       month="0"+inputMonth+"";
System.out.println(inputYear + "/" + month + "/" + day);
}

/** Check that the input has the correct numeric data already(yyyy, mm, dd)
* but in reversed order (dd/mm/yyyy)
* The year will never be smaller than the month or day
*/
public static boolean validateReverseOrder(String input) {
   String mm[]=input.split("/");
   int d=0,m=0,y=0;
   try {
       if(mm[0].charAt(0)=='0')
           d=mm[0].charAt(1)-'0';
       else
           d=Integer.parseInt(mm[0]);
       if(mm[1].charAt(0)=='0')
           m=mm[1].charAt(1)-'0';
       else
           m=Integer.parseInt(mm[1]);
       y=Integer.parseInt(mm[2]);
   }
   catch(NumberFormatException e) {
       return false;
   }
   if(y<m||y<d)
       return false;
return true;
}

/** Valid English format is <Month> <Day>, <Year>
* all other formats (besides the reversed order above)
* are considered invalid
* For students to complete
*/
public static boolean validateFormat(String[] input) {
   if(getMonthAsInt(input[0])<1)
       return false;
   int d=0,y=0;
   try {
       input[1]=input[1].substring(0,input[1].length()-1);
       if(input[1].charAt(0)=='0')
           d=input[1].charAt(1)-'0';
       else
           d=Integer.parseInt(input[1]);
       y=Integer.parseInt(input[2]);
   }
   catch(NumberFormatException e) {
       return false;
   }
   if(y<d)
       return false;
return true;
}

/** For students to complete
* Prompts the user for a filename, opens said file, reads in dates and
* converts the valid ones to ISO 8601 (YYYY/MM/DD) format
* call printDateISOFormat() to print dates to console
*/
public void readFile() throws IOException, FileNotFoundException {
Scanner scnr = new Scanner(System.in);
String filename = scnr.nextLine().trim(); //use trim() here or you'll have a newline on your filename
File f=new File(filename);
BufferedReader bf=new BufferedReader(new FileReader(f));
String l;
while((l=bf.readLine())!=null)
{
   if(l.equals("-1"))
       break;
   if(l.contains("/")) {// for checking dates containing '/'
       if(validateReverseOrder(l)) {
           String mm[]=l.split("/");
       int d=0,m=0,y=0;
           if(mm[0].charAt(0)=='0')
           d=mm[0].charAt(1)-'0';
       else
           d=Integer.parseInt(mm[0]);
       if(mm[1].charAt(0)=='0')
           m=mm[1].charAt(1)-'0';
       else
           m=Integer.parseInt(mm[1]);
       y=Integer.parseInt(mm[2]);
       printDateISOFormat(y,m,d);
       }
   }
   else {
       if(validateFormat(l.split(" "))) {
           String input[]=l.split(" ");
           int d=0,y=0,m=0;
           input[1]=input[1].substring(0,input[1].length()-1);
       if(input[1].charAt(0)=='0')
           d=input[1].charAt(1)-'0';
       else
           d=Integer.parseInt(input[1]);
       y=Integer.parseInt(input[2]);
       m=getMonthAsInt(input[0]);
       printDateISOFormat(y,m,d);
       }
   }
}
}

}

/////////////////////Sample Input

//////////////////Sample Output