what is the difference between '&' and '&&' in java

Question

Possible Duplicate:
& vs && and | vs ||
What are the cases in which it is better to use unconditional AND (& instead of &&)

While checking for the simple AND condition, i can use '&' and '&&'. It works fine with '&' and as well as '&&'. Is there any difference between those two.

sample code:

if(sample!=null & sample.size())
if(sample!=null && sample.size()

Your first line of code can throw a NullPointerException, but the second can't. That's the essential difference. — Marko Topolnik, Aug 20 '12 at 09:14

Ilya Shinkarenko · Answer 1 · 2012-08-20T09:53:42.917

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The first version (&) always evaluates both arguments. The second version (&&) evaluates the second argument only if the first argument has been evaluated to TRUE.

Same applies to the OR operator: there is | and ||. The (||) evaluates the second argument only if the first argument has been evaluated to FALSE.

edited Aug 20 '12 at 09:53

answered Aug 20 '12 at 09:14

Ilya Shinkarenko

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With the exception that the OR operator evaluates the second argument only if the first argument has been evaluated to *false*. – maba Aug 20 '12 at 09:28
Thanks @maba, the answer is updated – Ilya Shinkarenko Aug 20 '12 at 09:54

score 1 · Answer 2 · answered Aug 20 '12 at 09:14

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first expression check both sides, second expression checks 2nd side only if 1st is true.

answered Aug 20 '12 at 09:14

dantuch

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score 1 · Answer 3 · edited May 23 '17 at 11:48

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It evaluates both the left hand side and the right with just a singular &, even if the last hand side is false.

See my question below for the finer details...

When should I not use the Java Shortcut Operator &

edited May 23 '17 at 11:48

Community

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answered Aug 20 '12 at 09:14

David

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score 1 · Answer 4 · answered Aug 20 '12 at 09:14

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'&' for bit wise 'AND'
'&&' is for Logical 'AND'

answered Aug 20 '12 at 09:14

Siva Arunachalam

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Your statement is false and misleading. `&` is for both logical and bitwise operations. – Marko Topolnik Aug 20 '12 at 09:33

score 1 · Answer 5 · edited Aug 20 '12 at 12:30

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if(sample!=null & sample.size())

Here if first condition is not satisfied then also it will check next condition.

if(sample!=null && sample.size())

Here if first condition is not satisfied then also it will not check next condition.

edited Aug 20 '12 at 12:30

dantuch

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answered Aug 20 '12 at 09:15

Subhrajyoti Majumder

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score 1 · Answer 6 · answered Aug 20 '12 at 09:15

The && is a short-circuit operator meaning that if sample is null in your example, it will stop and not evaluate the second condition.

On the other side, the & is not short-circuit and will evaluate sample.size() even if sample is null. Of course in this case it will throw NullPointerException, but in the short-circuit case it won't.

what is the difference between '&' and '&&' in java

6 Answers6