Question from MindQ sun certified java programmer

[Rekha Gaikwad]

Consider the two statements:

1. boolean passingScore = false && grade == 70;
2. boolean passingScore = false & grade == 70;
The expression

grade == 70

is evaluated:




a) in both 1 and 2
b) in neither 1 nor 2
c) in 1 but not 2
d) in 2 but not 1
e) invalid because false should be FALSE



correct answer is d..

can any one explain?

[Kudret Serin]

&& and || operators are short circuit logical operators. It means in

 A && B  

if A is false, B is not evaluated. (Because there is no chance the result to be true if A is false)
In your example 1. passingScore is assigned to false and being evaluated, because it is false, grade==70 is not evaluated.
(In the second one & operator is not a schort circuit operator, rather bitweise and)

hope this helps

[Sakti Singh]

&& - Short Circuit AND
|| - Short Circuit OR

for AND :

false && any boolean (true/false) is always false, so && does not evaluate the 2nd part when first part if false ..

Similarly incase of || , if first part is true, the second part is not evaluated..

Hope this helps

[Rekha Gaikwad]

thanks alot..