Check if returned value is not null and if so assign it, in one line, with one method call

Question

Java is littered with statements like:

if(cage.getChicken() != null) {     dinner = cage.getChicken(); } else {     dinner = getFreeRangeChicken(); } 

Which takes two calls to getChicken() before the returned object can be assigned to dinner.

This could also be written in one line like so:

dinner = cage.getChicken() != null? cage.getChicken() : getFreeRangeChicken(); 

But alas there are still two calls to getChicken().

Of course we could assign a local variable then use the ternary operator again to assign it if it is not null, but this is two lines and not so pretty:

FutureMeal chicken = cage.getChicken(); dinner = chicken != null? chicken : getFreeRangeChicken(); 

So is there any way to say:

Variable var = some value if some value is not null OR some other value;

And I guess I'm just talking syntax here, after the code is compiled it probably doesn't make much difference how the code was written in a performance sense.

As this is such common code it'd be great to have a one-liner to write it.

Do any other languages have this feature?

Answer 1

Java lacks coalesce operator, so your code with an explicit temporary is your best choice for an assignment with a single call.

You can use the result variable as your temporary, like this:

dinner = ((dinner = cage.getChicken()) != null) ? dinner : getFreeRangeChicken(); 

This, however, is hard to read.

Answer 2

Same principle as Loki's answer but shorter. Just keep in mind that shorter doesn't automatically mean better.

dinner = Optional.ofNullable(cage.getChicken())   .orElse(getFreerangeChicken()); 

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Note: This usage of Optional is explicitly discouraged by the architects of the JDK and the designers of the Optional feature. You are allocating a fresh object and immediately throwing it away every time. But on the other hand it can be quite readable.