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Java Java Objects Harnessing the Power of Objects Exceptions

Posted by Morgan D'Antoni
Morgan D'Antoni
1,183 Points

What is iae.getMessage() and how does it work?

I'm following along with the lesson, and I don't understand how this code is able to return "Too many PEZ!!!" in the console:

    try {
      dispenser.fill(400);
      System.out.println("This will never happen.");
    } catch(IllegalArgumentException iae) {
      System.out.println("Whoa there!");
      System.out.printf("The error was %s", iae.getMessage());
    }

I never defined getMessage anywhere in my code, yet it still spits out the intended text. The only area where I wrote "Too many PEZ!!!" was in a different class:

public void fill(int pezAmount) {
   int newAmount = pezCount + pezAmount;
    if (newAmount > MAX_PEZ) {
     throw new IllegalArgumentException("Too many PEZ!!!"); 
    }
    pezCount = newAmount;
  }

Can someone please explain this to me?

1 Answer

Jason Larson
Jason Larson
8,361 Points

iae is a custom error that you created as part of your fill() method ( throw new IllegalArgumentException("Too many PEZ!!!") ). As part of that, you told it to send the message "Too many PEZ!!!" if the error was thrown. You then ran your method within a try/catch block and told the catch block to catch any iae errors ( catch(IllegalArgumentException iae) ). Since your method apparently triggered an IllegalArgumentException error, the catch block was called, where it ran the code you defined. What you may be confused about is the .getMessage() method on iae. I don't know Java, but I assume that this is a built-in method on errors.

Hopefully this clears it up for you, but if not, just reply and I'll see if I can clarify.

Morgan D'Antoni
Morgan D'Antoni
1,183 Points

Yes, thank you! I wasn't understanding that .getMessage() is a built-in method, but now I get it.