Is it possible to stop try catch from returning null

Question

If someone calls my method, I want to defensively deal with the problem. Usually I just return null.

I decided to implement a try catch but it looks like I just end up returning null anyway.

Can I write my try catch in such a way that at the end of method it doesn't return null?

Sample code, using peek on a Stack class.

    public T peek()
    {
        T temp = null;

        try
        {
            temp = array[size]; 
        }

        catch(Exception e)
        {
        }

        return temp;
    }

When called with an empty stack. It will return null.

So should I even bother with the try catch for this kind of case? I am tempted to do this:

if(isEmpty())
   return null;

If the stack is not empty I want to return the element. If the stack is empty then can I avoid returning null if I use the try-catch?

Related: [Avoiding “!= null” statements in Java?](http://stackoverflow.com/q/271526/1065197), just that in this case you avoid from `try/catch` block. — Luiggi Mendoza, Jun 04 '14 at 20:29
Do the if-else. try catch is an awful way to handle normal communications in a program. Its piss poor performance wise and is just ugly to look at — Totoro, Jun 04 '14 at 20:30
what do you want it to return ? And are doing to the try catch to handle IndexOutOfBoundException ? — CMPS, Jun 04 '14 at 20:30
I think the more valid question is what do you want to return instead of null? — claudekennilol, Jun 04 '14 at 20:32
If the function peek is failing, then why not let it throw an exception? — Anders Lindén, Jun 04 '14 at 20:33
If the stack is not empty I want to return the element. If the stack **is** empty then can I avoid returning null if I use the `try-catch`? — Mike John, Jun 04 '14 at 20:37
You avoid returning null if you do not catch anything, but let the calling function catch the exception. Then the function is technically never returning. — Anders Lindén, Jun 04 '14 at 20:37
Then why bother with `try-catch` I completely agree with @Totoro. — Mike John, Jun 04 '14 at 20:39
Use an [option type](http://java.dzone.com/articles/no-more-excuses-use-null). — Elliott Frisch, Jun 04 '14 at 21:05
I like the people blindly downvoting the question. Please explain why, I would like to see your reasoning. — Mike John, Jun 04 '14 at 21:36

Anders Lindén · Answer 1 · 2015-03-14T06:39:55.550

2

This is how I would approach the problem. By throwing an exception in the peek function, putting the duty of handling that exception in the caller. Why? Because I want an error to cause an explosion as big as possible. The peek method also became smaller. Also as you already agree on, returning null is lame.

public T peek() throws IndexOutOfBoundsException
{   
  return array[size]; 
}

and

try
{
  T top = thestack.peek();
  /* Do something with that object */
}
catch(IndexOutOfBoundsException e)
{
  /* Do something else */
}

edited Mar 14 '15 at 06:39

answered Jun 04 '14 at 20:42

Anders Lindén

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I would like to point out: that is not defensive programming, which is one of my tags. – Mike John Jun 04 '14 at 20:52
Isn't removing makeup defensive? The makeup would be returning even if the function call was exceptional. – Anders Lindén Jun 04 '14 at 21:28

Elliott Frisch · Answer 2 · 2014-06-04T22:36:39.073

1

It's hard to imagine the array[size] throwing an Exception, unless array is null or size is outside the length of array. So, you could do something like this -

 if (array != null && array.length > size) {
   return array[size - 1]; // assuming your size starts at 1
 }
 return null; // need to return something, if not null you need an option type.

Edit

Or, using an Option monad - and something like,

 if (array != null && array.length > size) {
   return new Some<T>(array[size - 1]); // assuming your size starts at 1
 }
 return new None<T>();

edited Jun 04 '14 at 22:36

answered Jun 04 '14 at 20:31

Elliott Frisch

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That would return null – Anders Lindén Jun 04 '14 at 20:35
1

@AndersLindén Was my comment "need to return something, if not null you need an option type." too subtle? – Elliott Frisch Jun 04 '14 at 20:37
Sorry, I only saw "return null;" and that was not subtle. Had to read more closely. – Anders Lindén Jun 04 '14 at 20:38

score 1 · Accepted Answer · answered Jun 04 '14 at 20:59

The method has to return something or throw an Exception. If you have an unbounded generic type, then things like null object patterns can't be used, so the options are returning null, returning something that contains T like Optional<T>, or throwing an Exception.

If you don't like the safety of null, you can use Optional, either from Java 8 or a library. Checked exceptions have a similar safety but are inappropriate here.

Is it possible to stop try catch from returning null

3 Answers3