What is the difference between these 2 ifs?

Question

if(loadFactor != null && !(trialExists(loadFactor))

and

if(!(loadFactor == null || trialExists(loadFactor))

I was asked in the review to make the 1st, if I change to the 2nd. How does it matter.

Answer 1

There is no difference.

In both cases:

• If loadFactornull, trialExists(loadFactor)it will not be evaluated, and the condition will be false, so it will not go into the bodyif
• Otherwise, it trialExists(loadFactor)will be evaluated, and the condition will be the opposite of the result - therefore, it will only enter the body of the operator ifif it trialExists(loadFactor)returns false

This is due to the fact that both &&are ||short-circuited:

• If the first operand &&is equal false, the second operand is not evaluated, and the result isfalse
• If the first operand ||is equal true, the second operand is not evaluated, and the result istrue

. : " , ". , " ", , , .

Answer 2

, De Morgan , Java.

"not (A B)" "( A) ( B)"

"not (A B)" "( A) ( B)"

( )

• , :

  loadFactor != null && !(trialExists(loadFactor)
  

• :

  !!(loadFactor != null && !(tiralExists(loadFactor))
  

• ( (A B) ( A) ( B))

  !(!(loadFactor != null) || !!(trialExists(loadFactor)))
  

• :

  !(loadFactor == null || trialExists(loadFactor))
  

2- .

Answer 3

. , loadFactor Null , , .

, , loadFactor Null.

Answer 4

, . && secnnd arg, , || second-arg, arg .

, , , .

, , trialExists() .