Question

A question about exceptions, the language is JAVA.

The purpose is writing a program that reads a string from the keyboard and tests whether it contains a valid time.
Display the time as described below if it is valid, otherwise display a message as described below.
The input date should have the format hh:mm:ss (where hh = hour, mm = minutes and ss =
seconds in a 24 hour clock , for example 23:47:55).
Here are the input errors (Exceptions) that your program should detect and deal with:
Receive the input from the user ( give an example of the format you are expecting the user to use
when entering the time ) and check for the following:
a. missing one of parts (the hour or the minutes or the second is missing.
b. hh, mm or ss is not numeric
c. hh not between 0 and 23
d. mm is not between 0 and 59
e. ss is not between 0 and 59

Be specific when reporting an error. For example, “The input 24:04:20 contains an invalid hour
of 24”.
If the user gives you invalid input, start the whole process again by asking the user for a valid
time. Keep prompting the user until you get a valid time. A while (!valid) loop would work well
here.
If the time is valid, then output a message in this format, “23:45:16 is 11:45:16 pm”. That is,
convert it to the am/pm format.

The program should be coded as a series of method calls (within the try block, inside the while loop):
1. getInput( ) – asks the user for the time. Uses the String split( ) method to break it into 3 parts.
Checks that there are 3 parts and throws a MissingColonException if there aren’t. The method
returns the String array.
2. checkHour( ) – receives the hour String part of the array, tries to convert it to a numeric value, then
checks if the number is between 0 and 23. Throws NumberFormatException and HourException
3. checkMinutes( ) – similar to checkHour( )
4. checkSeconds( ) – similar to checkHour( )

Notes:
1. Be sure that the output that you submit shows that your program has tested ALL the
different types of errors that can occur.
2. The messages output by the catch blocks should be very specific. For example, output “24 is an
invalid hour”, or “23:15 is missing one part”, rather than simply “invalid hour” or “invalid input”.
The first 2 messages allow the user to better understand what input caused the problem; the other
messages leave the user guessing about what the source of the problem is.
3. You do not need to write code for the NumberFormatException class; this already exists as
part of Java.
4. You’ll need to write class definition files for the other exceptions described above.

Answer 1

import java.util.*;
public class ValidTime
{
   //method to get input
   public static String[] getInput()
   {
       //prompt the user to enter an input
       System.out.print("Enter valid time:\t");
       Scanner sc = new Scanner(System.in);
       String time = sc.nextLine();
       //split the input
       String[] vals = time.split(":");
       return vals;
   }
   //method to check the hours are valid or not
   public static int checkHours(String time, String hour) throws Exception
   {
       //conver the string to integer
       int hours = Integer.parseInt(hour);
       //check whether the hours are in given range
       if(hours < 0 || hours > 23)
       {
           throw new HourException(time, hour);
       }
       return hours;
   }
   //method to check the minutes are valid or not
   public static int checkMinutes(String time, String minute) throws Exception
   {
       //conver the stirng to integer
       int minutes = Integer.parseInt(minute);
       //check whether the minutes are in given range
       if(minutes < 0 || minutes > 59)
       {
           throw new MinuteException(time, minute);
       }
       return minutes;
   }
   //method to chcek the seconds are valid or not
   public static int checkSeconds(String time, String second) throws Exception
   {
       //conver the string to integer
       int seconds = Integer.parseInt(second);
       //check the seconds are in given range
       if(seconds < 0 || seconds > 59)
       {
           throw new SecondException(time, second);
       }
       return seconds;
   }
   public static void main(String args[]) throws Exception
   {
       //iterate in an infinite loop
       while(true)
       {
           //call the method to get input
           String[] vals = getInput();
           String time = vals[0] + ":" + vals[1] + ":" + vals[2];
           try
           {
               //call the three functions
               int hours = checkHours(time, vals[0]);
               int minutes = checkMinutes(time, vals[1]);
               int seconds = checkSeconds(time, vals[2]);
               //if all are valid calculate the time in 12 hour format and print the output
               if(hours >= 12)
               {
                   hours = hours - 12;
                   if(hours == 0)
                   {
                       hours = 12;
                   }
                   System.out.println(time + " is " + hours + ":" + minutes + ":" + seconds + " pm");
                   break;
               }
               else if(hours == 0)
               {
                   hours = 12;
                   System.out.println(time + " is " + hours + ":" + minutes + ":" + seconds + " am");
                   break;
               }
               else
               {
                   System.out.println(time + " is " + hours + ":" + minutes + ":" + seconds + " am");
                   break;
               }
           }
           //catch the appropriate exception and print the output
           catch(NumberFormatException e)
           {
               System.out.println("Invalid Format");
           }
           catch(HourException e)
           {
               e.toString();
           }
           catch(MinuteException e)
           {
               e.toString();
           }
           catch(SecondException e)
           {
               e.toString();
           }
       }
      
   }
}
//class for hour exception
class HourException extends Exception
{
   //define the constructor to print the message
   HourException(String time, String hour)
   {
       System.out.println("The input " + time + " consists an invalid hour of " + hour);
   }
}
//class for minute exception
class MinuteException extends Exception
{
   //define the constructor to print the message
   MinuteException(String time, String minutes)
   {
       System.out.println("The input " + time + " consists an invalid minute of " + minutes);
   }
}
//class for second exception
class SecondException extends Exception
{
   //define the constructor to print the message
   SecondException(String time, String seconds)
   {
       System.out.println("The input " + time + " consists an invalid second of " + seconds);
   }
}

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