How am I catching an InputMismatchException here?

Question

I'm trying to catch InputMismatch exceptions and display a message that tells me where the exception occurred and what type of input is required. I need this to loop until the correct input is entered. I'm doing this by incrementing "statusCode" and "expectedCode" (which is what statusCode has to be to exit the loop. expectedCode increments before each loop, and statusCode increments at the end of each method. I have my exception-related methods and data in a different class so that accessing it is easier later.

When I enter the correct input the first time (an int), it works as intended. However, if I enter incompatible data, I first get an extra blank input line, and then after input on that, my exception is caught. The problem is that all input afterwards throws the exception, no matter what I enter, and I can't proceed.

An ExceptionTracker object called track is declared prior. Here is the relevant code:

  track.incrementExpected();          //expectedCode=1
  while(track.getStatusCode()!=track.getExpectedCode())
  {
     try
     {
        setGuests();            //statusCode=1 if successful
     }
     catch(InputMismatchException mis)
     {
        track.eventException();
     }
  }

the setGuests() method:

   public void setGuests()
   {
      guests=0;
      
      while(guests<5||guests>100)
      {
         System.out.print("How many guests will be attending? ");
         guests=input.nextInt();
         input.nextLine();
         if(guests<5)
            System.out.println("Events for fewer than 5 guests are not accepted.");
         else
            if(guests>100)
               System.out.println("Events for greater than 100 guests are not accepted.");
      }
      
      if(guests>=CUTOFF)
         PPG=BPPG;
      else
         PPG=SPPG;
      price=guests*PPG;
      track.incrementStatus();            //statusCode=1
   }

in the ExceptionTracker class:

   public void incrementExpected()
   {
      ++expectedCode;
   }
   
   public void incrementStatus()
   {
      ++statusCode;
   }
   
   public void eventException()
   {
      input.nextLine();
      System.out.println("Error code: "+statusCode);
      switch(statusCode)
      {
         case 3:
         case 1:
            System.out.println("Input must be of type int.");
            break;
         
         case 2:
         case 0:
            System.out.println("Input must be of type String.");
            break;
      }
  }

Assistance is appreciated.

Edit: Stack trace is as follows

java.util.InputMismatchException
    at java.base/java.util.Scanner.throwFor(Scanner.java:939)
    at java.base/java.util.Scanner.next(Scanner.java:1594)
    at java.base/java.util.Scanner.nextInt(Scanner.java:2258)
    at java.base/java.util.Scanner.nextInt(Scanner.java:2212)
    at Event.setGuests(Event.java:106)
    at Event.<init>(Event.java:38)

You should start by printing the stack trace to see what the message is, not simply hiding the error. — chrylis -cautiouslyoptimistic-, Apr 16 '21 at 16:27
@chrylis-cautiouslyoptimistic- added stack trace to end of post, thanks for the advice, I'll remember it for the future. — timestopMachinist, Apr 16 '21 at 16:57

score 0 · Accepted Answer · answered Apr 16 '21 at 20:25

0

It sounds like he did not discard your old input. Make sure it is reseted when the loop circle restarts.

answered Apr 16 '21 at 20:25

Nasten1988

86
8

This ended up being what the problem was, but can you explain how? I had to move `input.nextLine()` to the catch block, and out of my `eventException` method, but why wasn't it working there? In earlier tests, it worked fine clearing the line in my method, but then it just started prompting for an input of its own. I'll be marking this as answer but I'm hoping for a bit more explanation if possible, so that I dont make the same mistake again later. – timestopMachinist Apr 16 '21 at 23:27
Depending on your track class the lifespan of your input (old) ends after bracket is closed, I don't have the whole code to see for myself I would guess, on what I see, the old input was already cleared from the memory when the new compare happens. So he compared NULL with your Exception Code and that's never the same. If you like send me your old and new Code as textile and I have a better look, but iam not a pro in Java. – Nasten1988 Apr 17 '21 at 11:57

How am I catching an InputMismatchException here?

1 Answers1