Comments on: Why not to initialize your local variables at declaration

By: Thor M

Thor M — Sat, 22 Dec 2007 22:24:33 +0000

Consider the following code I often see:

void ...(...)
{
   object o = null;
   object o = DoSomething(...);
   if (object != null)
   {
      ...
   }
}

It's a stupid double assignment. The DoSomething method assigns to variable because it always returns a value or throws an exception. It's a case where the compiler could easily outwit the *programmer*.

By: Vincent Partington

Vincent Partington — Fri, 13 Oct 2006 14:34:46 +0000

Exactly. Instead of Try to initialize local variables where they\’re declared it should have said Try to declare local variables where they\’re initialized. Then the compiler could prevent a lot of these initialization problems instead of users getting an NPE at runtime.

Regards, Vincent.

By: erozendaal

erozendaal — Fri, 13 Oct 2006 13:58:29 +0000

To me the sun standards recommend that the declaration of a local variable should be moved to where it is first assigned (initialized). This way the variable is _always_ initialized with a correct value.

Only if this is not possible (for example, due to some computation that cannot be extracted into a separate method) would you declare a local variable without initializing. Like you said, assigning “null” or some other random value is a bad thing in this case since the compiler is no longer able to help you avoid errors.