Question

I think this is a dumb question but I hear and see the term exception handling a lot. I have used try/catch, but i am still wondering what on earth ‘handling‘ means. Can anyone kindly give some example that we can say the exception is actually ‘handled‘?

sorry for poor English, hope i made myself clear.

Answer 1

It means catching an Exception and performing some logic based on its type, so that your application can handle it gracefully rather than abruptly shutting down.

Here is an example (albeit a contrived one) in Java:

public int arrayRetrieve(int[] a, int index) {
   return a[index]; 
}

Given this function, there is no guarantee that index will be a valid position in a. In Java, this will throw an ArrayOutOfBoundsException.

Code that calls arrayRetrieve needs to be aware of this possibility, and handle this case accordingly:

int num = 0;
try {
    num = arrayRetrieve(someArray, 77);
}  catch (ArrayOutOfBoundsException e) {
    // Set num to a default value, or log an error, or however you want to handle this case
}

If the ArrayOutOfBoundsException were not caught, this would cause the program to crash instead.

(One reason I said this example is contrived is because Java in particular has two kinds of Exception – the kind you have to catch explicitly, and the kind you don’t. ArrayOutOfBoundsException is an example of the latter.)