CODEWITHSUNDEEP
javanullcomparisoncompare
JiniKJohny
JiniKJohny

Reputation: 1182

Difference between null!=variable and variable!=null

What is the difference between null!=variable and variable!=null Which method is perfect to use?

if ((null != value1) || (null != value2) || (null != value3)) {
            .......
            .......
            .......
}

or 

if ((value1 != null) || (value2 != null) || (value3 != null)) {
                .......
                .......
                .......
}

Please suggest the best one and the logical change between these?

Upvotes: 7

Views: 5264

Answers (6)

bbaassssiiee
bbaassssiiee

Reputation: 6782

In C assignment looks similar to comparison:

lvalue = rvalue;
lvalue == rvalue;

lvalues (variables) can be assigned to. rvalues can be expressions. Null cannot be assigned to, so if you adhere to use null as the lvalue in comparison, then the compiler will catch the ommision of the second equal sign in a statement like

null = rvalue;

Where you might accidentally assign null with:

lvalue = null;

Upvotes: 2

Ananth
Ananth

Reputation: 797

Both the ways of comparision are correct.There is logically no difference but programmers prefer to use value!=null.

Upvotes: 3

Owen Cao
Owen Cao

Reputation: 8183

null != value is a hold-over from C. In C, your code will be compiled with no warning in this way: if (variable = null) (it's a wrong code), while you actually probably meant if (variable == null).

But in Jave both these two styles are OK.

Upvotes: 2

Alex Gwartney
Alex Gwartney

Reputation: 87

As others have mentioned there is not a difference but I haven't ran across something that is 

null != value2

I always see it as value2 !=null and like thihara said its easier for readability. I think its also good to keep it the way value != null for beginner programmers who could possibly go over some ones code might get a little lost on the concept even though there is no difference.

Upvotes: 1

Thihara
Thihara

Reputation: 6969

Nothing is different.

I prefer value != null for purely readability reasons.

Upvotes: 4

Peter Pei Guo
Peter Pei Guo

Reputation: 7870

No difference.

But people quite often write "abc".equals(foo), instead of foo.equals("abc"), to avoid null point exception.

Upvotes: 6

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