[Newbie] What'is the best practice?

[Max Bean]

If I wanna write the method which return any kind of Object, what's the cleaner and most efficient code to check the initial state and check whether it's null or not?

Another thing is the invoker. If I can guarantee that method will return at least null to the invoker, how can I protect NullPointerException in the point of view of the invoker?

Please do not consider this question as stupidity. I'm really noobiest...

[Joanne Neal]

Object myObj = myMethod();
if (myObj == null) {
  // Method returned null
} else {
  // myObj references a valid object
}

[Raghavan Muthu]

Originally posted by Maximilian Boonyoung:

If I wanna write the method which return any kind of Object,
what's the cleaner and most efficient code to check the initial state and check whether it's null or not?

For which you can have a code snippet like this.

public Object myMethod()
{
  Object objToReturn = null;
 
  //do whatever you want to implement
  // and assign the *actual* object to be returned to the
  // "objToReturn" variable
 
  return objToReturn;
}

Originally posted by Maximilian Boonyoung:

Another thing is the invoker. If I can guarantee that method will return
at least null to the invoker, how can I protect NullPointerException in
the point of view of the invoker?

As you know the method could return *any kinda* object, you should
typecast the returned object before its first use.

Let's say you have an object being returned of type MyClassObj. (It
can be of any other object like String, ArrayList etc).

 
MyClassObj obj1 = (MyClassObj) myMethod();
 
/* Just to avoid NullPointerException */
 
if(obj1!=null)
{
  //object returned is NOT null
  // can proceed with the actual requirement
}
 
/* If really required to let the user know that returned object is NULL,
 you can reverse the condition and have a message intimating the same */
 

Does this help?
[ August 17, 2007: Message edited by: Raghavan Muthu ]

[Stan James]

If that all worked for you, let's take another step and talk about why you want to return null. It's a pain for the caller to have to test and it's often unclear exactly what we're trying to tell somebody when we return null. We have ways of making life easier for the caller in almost any program.

[marc weber]

Originally posted by Maximilian Boonyoung:
... Please do not consider this question as stupidity. I'm really noobiest...

I think it's a great question! In fact, it turns out there can be big differences of opinion about whether returning null is a good idea.

How this is handled depends a lot on the context of the problem. So as Stan suggested, "let's take another step and talk about why you want to return null."

[Raghavan Muthu]

Originally posted by marc weber:

I think it's a great question! In fact, it turns out there can be big differences of opinion about whether returning null is a good idea.

Yes, very much. I agree with Marc.

This makes us think on taking a decision should we really need to return null?