Wednesday, November 4, 2009

Casting an object if the object is NULL?

If you are casting an object which is null, then java will not throw any exceptions. What does is, it will simply assign the null to the casted reference type variable.

Object obj = null;

String a = (String) obj;

In above example "a" will be assigned as NULL.

ava.util.ArrayList al = session.get("xyzObject");

Object o = (Object) al;

String a = (String) o;


If session.get("xyzObject") != NULL:

    If we are getting an arraylist object from session then the above code will throw Class Cast Exception.

If session.get("xyzObject") == NULL:

    If we are getting a null value from session then the above code will not throw any exceptions. The reasons because null can be cast to any object references.

What's a big thing in it:

    The main thing is if we are sending null to an object reference most of time, and some time if we are start sending a value in it, it may break the code...

Hope this post may give some thoughts. Please leave your comments if any.


ppow said...

There is no reason why an exception would be thrown, as NULL references are valid parts of the language.

If in your code you want the passed object not to be null you should check that yourself and manually throw NullPointerException if necessary.

Jobu said...

sounds good...

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