Computer Science : Evaluating Boolean Expressions

Study concepts, example questions & explanations for Computer Science

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Example Questions

Example Question #47 : Standard Data Structures

int currentYear = 2016;

bool leapYear;

 

if (currentYear % 4 == 0) {

leapYear = true;

} else {

leapYear = false;

}

 

febDays = leapYear ? 28 : 29

Based on the code above, what value will febDays have?

Possible Answers:

Correct answer:

Explanation:

The ternary operator works as follows:

(condition to be checked) ? (value to return if true) : (value to return if false)

The answer is purposely logically incorrect to force you to consider the structure of the code. While 2016 is obviously a leap year where February should have 29 days, the ternary operator used is set to return 28 days if true and 29 if false. So in this case, febDays will be 28.

Example Question #1 : Evaluating Boolean Expressions

What does the following code print?

int i = 3;

int j = 4;

int k = 5;

int l = i * k - j; 

int m =  i*2 + j + k; 

if ( ( l > m ) || ( l * i ) = (m+m+i) )

   System.out.println("The statement proves true");

else

   System.out.println("The statement proves false");

Possible Answers:

Compiler Error

The statement proves true.

The statement proves false.

Runtime Error

Correct answer:

Compiler Error

Explanation:

In the second condition, it is not a statement of equivalence but a statement of assignment. This would cause it to have a runtime error. If it was to be a == instead of =, the statement would be true.

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