CODEWITHSUNDEEP
javaif-statementintellij-ideademorgans-law
subject-q
subject-q

Reputation: 135

Is !(~A && ~B) better than (A||B) in programming?

I am developing in Java and I am using IntelliJ as my IDE. I wrote an if statement as follows.

if( list1.size() >= 1 || list2.contains(itemX) ) {
    //do something
}

IntelliJ suggested a transformation (DeMorgan's Law) and it transformed it to:

if( ! ( list1.size() < 1 && !( list2.contains(itemX) ) ) ) {
    //do something
}

So it applied a very common discrete mathematics theory on simplifying boolean expressions. What I am wondering is how does this optimize anything?

|| operator anyways does not execute the whole condition if the first part is itself true, and only executes the RHS only if the first part is false.

Is the transformed condition effective? How?

Upvotes: 0

Views: 746

Answers (2)

vizsatiz
vizsatiz

Reputation: 2173

This is somewhat subjective, but a good general rule of thumb is to remove as much complexity as possible. By complexity, I mean the number of operations you need to perform in order to obtain the desired result.

In this sense, !a && !b is worse than !(a || b) because in one case you're negating a and b, then performing the OR and operator resulting in 3 operations whereas in the latter case, you're only performing 2. Of course this is vacuous when you're talking about two conditions, but when you're dealing with many, this can make a big difference.

But in your scenario it doesn't make any sense for your IDE to change it as the later has lower number of operations. Probably its the IDE trying to desperately woo you :)

Hope this makes sense !!

Upvotes: 5

Twini
Twini

Reputation: 195

Both are exactly the same statements.

I agree that OR operator does not evaluate the second part if the first part is TRUE, however, it is also true that the AND operator does not evaluate the second part if the first part is FALSE.

In fact, it will take more time and space to evaluate the ~(~A && ~B) as opposed to A||B.

Hope this helps :)

Upvotes: 4

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