IF statement

[Ananth Ram]

Hi All,

Just curious to know the difference in the below if statements.

Vector vTest = new Vector();

if ( vTest != null )

and

if ( null != vTest)


Thanks,

Ananth Ram

[avi sinha]

i think there is no any difference between them.

avi sinha

[fred rosenberger]

There's no real functional difference. but imagine you were doing an equals test (==), and mistyped it as '='

vTest = null

vs

null = vTest

The compiler would flag this in either case (since neither evaluate to a boolean True or False). However, other languages like C++ would happily let you assign null to vTest and continue on, causing all kinds of strange things to happen in your code.

[avi sinha]

fred rosenberger wrote:There's no real functional difference. but imagine you were doing an equals test (==), and mistyped it as '='

vTest = null

vs

null = vTest

The compiler would flag this in either case (since neither evaluate to a boolean True or False). However, other languages like C++ would happily let you assign null to vTest and continue on, causing all kinds of strange things to happen in your code.

i agree sir.
in case of assignment it can lead to compilation error.

avi sinha

[Vikash Ananda]

Hi,

Implementation wise there is some difference. Suppose you have created Vecor object and doing some operations on it and at some point of time you want to check wether it has become null or not.

 if ( vTest != null )

and

if ( null != vTest)   

If you are using first case: if ( vTest != null ) and suppose that vTest is null then on run time the application will throw NullPointerException.

If you are using second case: if ( null != vTest) and suppose that vTest is null then on run time the application will not throw NullPointerException.

Second case is good coding practice.

Thanks,
Vikash Anand.

[Rahul P Kumar]

Vikash Ananda wrote:

If you are using first case: if ( vTest != null ) and suppose that vTest is null then on run time the application will throw NullPointerException.

It will throw NullPointerException only when there is some operation on vTest. In that if statement i don't think it will throw such exception.