Question

Possible Duplicate:
A better way to compare Strings which could be null

I have an if condition which looks like this :

if( !str1.equals(str2) )
{
    ---
    ---
    ---
}

where str1 and str2 are two string objects.

There are chances that str1 might be null , so is the below code equivalent to the above, along with handling the null check?

if( !(str1==null ? str2==null : str1.equals(str2)) )
{
    ---
    ---
    ---
}

Thanks!

Answer 1

Yes, that will lead to the same result.

To be a bit more specific:

1. If str1 isn’t null, it’s exactly the same, since it just passes through the ternary check to the same expression as before
2. If str1 is null, it then becomes a check to see if str2 is also null.

And since you have the whole ternary expression wrapped up with the ! out front, that behaves the same as before.

If you wanted to be a bit more clear, you could make str2==null into an actual comparison between str1 and str2: str1==str2. Since one of the values is already null, it doesn’t matter that it’s a referential check instead of a proper string equality check, and ends up being a bit more clear in the code (to me, anyways)

As others have mentioned, however, the Apache Commons library already includes this null-safe equality capability, but it does require a rather substantial library inclusion. On the other hand, many feel that the Apache Commons functionality should be effectively considered a part of Java itself, so you can decide for yourself if you want the extra dependency.

Lastly, the functionality isn’t technically equivalent, since the default .equals() method will throw a NullPointerException, while your equality check code won’t. If that is the behavior you were looking for (which I assume it is), then you’re fine, but it is something to be aware of.