Quiz U3B - CSA

Which is an equivalent way to write the following boolean expression? Assume that x and y are int variables that have been properly declared and initialized.

!(x == 4 && y <= 5)

• x !=4 && y >= 5

• x != 4 && y > 5

• x != 4 || y >= 5

• x != 4 || y > 5

Which is an equivalent way to write the following boolean expression? Assume that x is an int variables that have been properly declared and initialized.

!(x >= 5 || x != 3)

• x <= 5 && x == 3

• x < 5 || x == 3

• x <= 5 || x == 3

• x == 3

Answer explanation

x < 5 && x == 3 is an equivalent expression using DeMorgan's Law (I didn't give you this as a choice though!). But if x is both less than 5 and equal to, then the only way those statements can both be true is if x is exactly 3.

Which if case would check whether an int variable ppm is between 29 and 31, inclusive?

• if(29 <= ppm <= 31)

• if(29 <= ppm || ppm <= 31)

• if(29 <= ppm && ppm <= 31)

• if(ppm - 30 <= 1)

Which if case would check if water is NOT in liquid form based on a temperature variable named temp of type double, measured in Fahrenheit? Recall that water freezes at 32 and boils at 212.

• if(temp <= 32 || temp >= 212)

• if(temp <= 32 && temp >= 212)

• if(32 <= temp <= 212)

• if(temp >= 32 && temp <= 212)

Consider the following variables that represent time:

int hour; // valid range: 0 - 23

int minute; // valid range: 0 - 59

Which one of the following expresses the interval from 7:15 to 9:15?

• hour == 7 || hour == 8 || hour == 9 && minute <= 15

• hour == 7 && minute >= 15 || hour == 9 && minute <= 15

• hour >= 7 && minute >= 15 || hour <= 9 && minute <= 15

• hour == 7 && minute >= 15 || hour == 8 || hour == 9 && minute <= 15

• hour == 7 || minute >= 15 && hour == 8 && hour == 9 || minute <= 15

int y = 5;

int x = 0;

Which of the following if cases will not crash? [Short Circuit Evalution!]

• if(y / x > 1)

• if(x != 0 && y / x > 0)

• if(y / x > 0 && x != 0)

• if(x != 0 || y / x > 0)

The boolean expression (A || B) && A is true...

• whenever A is true

• whenever B is true

• whenever either A is true or B is true

• whenever both A is true and B is true

• In all cases

The boolean expression (A || !B) && B is true...

• whenever A is true

• whenever B is true

• whenever either A is true or B is true

• whenever both A is true and B is true

• In all cases

Which expression is equivalent to...

(x < 20) || (y > 10 && y < 20)

• (x < 20 && y > 10) || (x < 20 && y < 20)

• (x < 20 || y > 10) && (x < 20 || y < 20)

• (x < 20 || y > 10) && (y < 20)

• x < 20 || y > 10 || y < 20

What is the correct way to check if two String variables are equal to each other?

String a = ...;

String b = ...;

• a.equals(b)

• a = b

• a == b

• a - b = 0