which one to choose between calling a function twice and storing the return value in a variable?

Question

I have the following scenario.. and I come across the similar scenario many a times. Which is more preferable of the following two options?

Option-1:

String result = ( getDetails(...) == null ) ? "" : getDetails(...);

Option-2:

String returnValue = getDetails(...);
String result = ( returnValue == null ) ? "" : returnValue;

Which is more preferable and/or a good practice.?

option 2 is better readable. Furthermore you call getDetails only once. — nano_nano, Jul 12 '13 at 11:07
You probably meant `String result = returnValue == null ? "" : returnValue;`. And the better solution would probably be to make sure that `getDetails` never returns `null`. — assylias, Jul 12 '13 at 11:08
Never code for performance, code for readability http://stackoverflow.com/questions/1923795/java-method-invocation-s-using-a-variable — sanbhat, Jul 12 '13 at 11:09
@TheNewIdiot: Yes it is. Thanks for all your views and suggestions. — subbu, Jul 15 '13 at 12:27

score 4 · Answer 1 · answered Jul 12 '13 at 11:06

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Imho The second one is better because it's avoiding calling getDetails(...) method twice.

answered Jul 12 '13 at 11:06

Suresh Atta

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score 3 · Answer 2 · edited May 23 '17 at 12:13

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If you have to do that check for every call of getDetails then the best way would be getDetails method to return "" in cases when you return null.

Also calling the same method twice (which is probably idempotent in your case) is not a good practice even if it is very simple.

Please read this java-how-expensive-is-a-method-call. Main idea is don't do premature optimization, but you should get used to these simple cases when you can write better code

edited May 23 '17 at 12:13

Community

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answered Jul 12 '13 at 11:13

Tala

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Thanks for the clarification. But, the example was chosen randomly. – subbu Jan 07 '15 at 12:24

score 1 · Answer 3 · answered Jul 12 '13 at 11:15

I'd prefer the second option because it is more readable, especially when using the ternary operator.

If it is a problem or not to call getDetails(...) twice depends on your method. If it is a simple getter, the JVM might optimize the call and directly use the value so storing it in a local variable does not make a difference.
If it is a more complex method, e.g. a query to the database, I would definitely store the result in a local variable.

Generally speaking: Care about code readability first! If you find performance problems later on, try optimizing then.

score 1 · Accepted Answer · edited May 23 '17 at 11:52

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Option-2: is better

Option-1: Results in extra method call and such cases should always be avoided unless getDetails(...) is a getter method (a one liner method which returns something)

If you dig down to micro optimization, a method call generally results in

allocation of stack for the method variables
jumping the instruction set

which are couple of many overheads. As many say, such performance optimization should be left to Compiler and the code should be written to be more readable.

edited May 23 '17 at 11:52

Community

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answered Jul 12 '13 at 11:15

sanbhat

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Hi Sanbhat. Can I have a question relates to this post? I am not talking about Performance (CPU time consuming). I am talking about Memory consuming. As I know, for each getter call, JVM need to create a new Stack so my question is Do you think Option 1 will consume more memory than Option 2 ( I assume that getDetails called a lot )? Thanks. – LHA Mar 21 '14 at 16:21

score 0 · Answer 5 · answered Jul 12 '13 at 12:06

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option-2 will be always optimized one what ever you wrote in the calling function. Even if you are writing any in-build function or expression two times it will take fraction of section more than option-2.

answered Jul 12 '13 at 12:06

Jagannath Behera

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which one to choose between calling a function twice and storing the return value in a variable?

5 Answers5

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