is it a bad practice to declare objects as 'null'

Question

So I just came back from a 'meting' about a fix that we had to do which would fix an issue we had in production. Before the code goes out, it has to be presented to all these bunch of people. hate it!

Broken code (pseudo):

SomeClassA object1 = null
while loop
{
    if (some condition){
      // do something
    }
    else {
      object1 = someOtherObject.getValueForObject1();
    }
Record Date = object1.getRecordDate(); //this gets moved in fix
}

Suggested Code fix (pseudo)

SomeClassA object1 = null
while loop
{
    if (some condition){
      // do something
    }
    else {
      object1 = someOtherObject.getValueForObject1();
      Record Date = object1.getRecordDate();   
    }    
}

Code fix after suggestions (pseudo):

while loop
{
    if (some condition){
      // do something
    }
    else {
      SomeClassA object1 = null
      object1 = someOtherObject.getValueForObject1();
      Record Date = object1.getRecordDate();   
    }    
}

Broken code gave a Null pointer exception because for a record the control never went into the else block...which in turn kept object1 as null.

I'm sure people out there have encountered this type of issue. what are your stories/or suggestions? is it always a good practice to declare variables when they are needed instead of on top (I think Effective Java says that).. Is it a bad practice to declare object as 'null'

Answer 1

If you need to use object1 outside of the else block (which is the issue in the first and second examples but is taken care of in the third), then it needs to be declared somewhere else in the code structure.

If you want to keep using null as the initialization value, just remember to check for a null value before using the object.

Answer 2

Initializing with null here is a waste of time:

while loop
{
    if (some condition){
      // do something
    }
    else {
      SomeClassA object1 = null;
      object1 = someOtherObject.getValueForObject1();
      Record Date = object1.getRecordDate();   
    }    
}

Just do this:

while loop
{
    if (some condition){
      // do something
    }
    else {
      SomeClassA object1 = someOtherObject.getValueForObject1();
      Record Date = object1.getRecordDate();   
    }    
}

To answer your question, if a variable is not immediately used but is required in multiple scopes - I initialize it to null when I declare it.

Answer 3

A few tips:

1. When you declare an Object, in Java, C++, C# it is allays null, so please get rid of the "= null" thing.
2. Yes it is a very good idea to minimize the scope for every declared object. This means that if you need an object only for the else statement then declare it in the else statement.

Answer 4

1. it is a good practice to declare variables when they are needed instead of on top (I think Effective Java says that).. minimize the scope.

2. it is not a bad practice to declare object as 'null'. Most modern compiler will automatically optimize the object to null if a user does not do so. so it is good to assign to null.