Chapter 5: Loops Self Test Questions

Question 1

How many times will the following code print “Welcome to Java”?

int count = 0;
while (count < 10) {
System.out.println(“Welcome to Java”);
count++;
}

Answer 1

10

Question 2

Analyze the following code. Please select all that apply.

int count = 0;
while (count < 100) {
// Point A
System.out.println(“Welcome to Java!”);
count++;
// Point B
}

// Point C
A. count < 100 is always true at Point A
B. count < 100 is always true at Point B
C. count < 100 is always false at Point B
D. count < 100 is always true at Point C
E. count < 100 is always false at Point C

Answer 2

A & E

Question 3

What will be displayed when the following code is executed?

int number = 6;
while (number > 0) {
number -= 3;
System.out.print(number + “ “);
}

Answer 3

3 0

Question 4

How many times will the following code print “Welcome to Java”?

int count = 0;
do {
System.out.println(“Welcome to Java”);
count++;
} while (count < 10);

Answer 4

10

Question 5

How many times will the following code print “Welcome to Java”?

int count = 0;
do {
System.out.println(“Welcome to Java”);
} while (count++ < 10);

Answer 5

11

Question 6

How many times will the following code print “Welcome to Java”?

int count = 0;
do {
System.out.println(“Welcome to Java”);
} while (++count < 10);

Answer 6

10

Question 7

What is the value in count after the following loop is executed?

int count = 0;
do {
System.out.println(“Welcome to Java”);
} while (count++ < 9);
System.out.println(count);

Answer 7

10

Question 8

Analyze the following statement:

double sum = 0;
for (double d = 0; d < 10;) {
d += 0.1;
sum += sum + d;
}

A. The program has a compile error because the adjustment is missing in the for loop.
B. The program has a compile error because the control variable in the for loop cannot be of the double type.
C. The program runs in an infinite loop because d < 10 would always be true.
D. The program compiles and runs fine.

Answer 8

The program compiles and runs fine.

Question 9

Which of the following loops correctly computes 1/2 + 2/3 + 3/4 + … + 99/100?

A:
double sum = 0;
for (int i = 1; i <= 99; i++) {
sum = i / (i + 1);
}
System.out.println(“Sum is “ + sum);

B:
double sum = 0;
for (int i = 1; i < 99; i++) {
sum += i / (i + 1);
}
System.out.println(“Sum is “ + sum);

C:
double sum = 0;
for (int i = 1; i <= 99; i++) {
sum += 1.0 * i / (i + 1);
}
System.out.println(“Sum is “ + sum);

D:
double sum = 0;
for (int i = 1; i <= 99; i++) {
sum += i / (i + 1.0);
}
System.out.println(“Sum is “ + sum);

E:
double sum = 0;
for (int i = 1; i < 99; i++) {
sum += i / (i + 1.0);
}
System.out.println(“Sum is “ + sum);

Answer 9

c & d

Question 9

Which of the following loops correctly computes 1/2 + 2/3 + 3/4 + … + 99/100?

A:
double sum = 0;
for (int i = 1; i <= 99; i++) {
sum = i / (i + 1);
}
System.out.println(“Sum is “ + sum);

B:
double sum = 0;
for (int i = 1; i < 99; i++) {
sum += i / (i + 1);
}
System.out.println(“Sum is “ + sum);

C:
double sum = 0;
for (int i = 1; i <= 99; i++) {
sum += 1.0 * i / (i + 1);
}
System.out.println(“Sum is “ + sum);

D:
double sum = 0;
for (int i = 1; i <= 99; i++) {
sum += i / (i + 1.0);
}
System.out.println(“Sum is “ + sum);

E:
double sum = 0;
for (int i = 1; i < 99; i++) {
sum += i / (i + 1.0);
}
System.out.println(“Sum is “ + sum);

Answer 9

c & d

Question 10

The following loop displays _______________.

for (int i = 1; i <= 10; i++) {
System.out.print(i + “ “);
i++;
}

Answer 10

1 3 5 7 9

Question 11

Do the following two statements in (I) and (II) result in the same value in sum?

(I):
for (int i = 0; i < 10; ++i) {
sum += i;
}

(II):
for (int i = 0; i < 10; i++) {
sum += i;
}

Answer 11

yes

Question 12

What is the output for y?

int y = 0;
for (int i = 0; i < 10; ++i) {
y += i;
}
System.out.println(y);

Answer 12

45

Question 13

What is i after the following for loop?

int y = 0;
for (int i = 0; i < 10; ++i) {
y += i;
}

Answer 13

undefined

Question 14

Is the following loop correct?

for ( ; ; );

Answer 14

yes

Question 15

Analyze the following fragment:

double sum = 0;
double d = 0;
while (d != 10.0) {
d += 0.1;
sum += sum + d;
}
A. The program does not compile because sum and d are declared double, but assigned with integer value 0.
B. The program never stops because d is always 0.1 inside the loop.
C. The program may not stop because of the phenomenon referred to as numerical inaccuracy for operating with floating-point numbers.
D. After the loop, sum is 0 + 0.1 + 0.2 + 0.3 + … + 1.9

Answer 15

C. The program may not stop because of the phenomenon referred to as numerical inaccuracy for operating with floating-point numbers.

Question 16

Analyze the following code. Please select all that apply.

public class Test {
public static void main (String[] args) {
int i = 0;
for (i = 0; i < 10; i++);
System.out.println(i + 4);
}
}

Answer 16

C. The program compiles despite the semicolon (;) on the for loop line, and displays 14.

D. The for loop in this program is same as for (i = 0; i < 10; i++) { }; System.out.println(i + 4);

Question 17

How many times is the println statement executed?

for (int i = 0; i < 10; i++)
for (int j = 0; j < i; j++)
System.out.println(i * j)

Answer 17

45

Question 18

A. B. C. D.
1 1 2 3 4 5 6 1 1 2 3 4 5 6
1 2 1 2 3 4 5 2 1 1 2 3 4 5
1 2 3 1 2 3 4 3 2 1 1 2 3 4
1 2 3 4 1 2 3 4 3 2 1 1 2 3
1 2 3 4 5 1 2 5 4 3 2 1 1 2
1 2 3 4 5 6 1 6 5 4 3 2 1 1

Which pattern is produced by the following code?

for (int i = 1; i <= 6; i++) {
for (int j = 6; j >= 1; j–)
System.out.print(j <= i ? j + “ “ : “ “ + “ “);
System.out.println();
}

Answer 18

Pattern C

Question 19

How many times is the println statement executed?

for (int i = 0; i < 10; i++)
for (int j = 0; j < 10; j++)
System.out.println(i * j);

Answer 19

100

Question 20

To add 0.01 + 0.02 + … + 1.00, what order should you use to add the numbers to get better accuracy?
A. add 0.01, 0.02, …, 1.00 in this order to a sum variable whose initial value is 0.
B. add 1.00, 0.99, 0.98, …, 0.02, 0.01 in this order to a sum variable whose initial value is 0.

Answer 20

A. add 0.01, 0.02, …, 1.00 in this order to a sum variable whose initial value is 0.

Question 21

Analyze the following code.

double sum = 0;
for (double d = 0; d < 10; sum += sum + d) {
d += 0.1;
}
A. The program has a syntax error because the adjustment statement is incorrect in the for loop.
B. The program has a syntax error because the control variable in the for loop cannot be of the double type.
C. The program compiles but does not stop because d would always be less than 10.
D. The program compiles and runs fine.

Answer 21

D

Question 22

Will the following program terminate?

int balance = 10;

while (true) {
if (balance < 9)
break;
balance = balance - 9;
}
A. Yes
B. No

Answer 22

yes

Question 23

What is sum after the following loop terminates?

int sum = 0;
int item = 0;
do {
item++;
sum += item;
if (sum > 4)
break;
}
while (item < 5);

Answer 23

6

Question 24

What is the output after the following loop terminates? int number = 25; int i; boolean isPrime = true; for (i = 2; i < number && isPrime; i++) { if (number % i == 0) { isPrime = false; } } System.out.println("i is " + i + " isPrime is " + isPrime); A. i is 5 isPrime is true B. i is 5 isPrime is false C. i is 6 isPrime is true D. i is 6 isPrime is false

Answer 24

D. i is 6 isPrime is false

Question 25

What is the output after the following loop terminates? int number = 25; int i; boolean isPrime = true; for (i = 2; i < number; i++) { if (number % i == 0) { isPrime = false; break; } } System.out.println("i is " + i + " isPrime is " + isPrime); A. i is 5 isPrime is true B. i is 5 isPrime is false C. i is 6 isPrime is true D. i is 6 isPrime is false

Answer 25

B. i is 5 isPrime is false

Question 26

What is sum after the following loop terminates? int sum = 0; int item = 0; do { item++; if (sum >= 4) continue; sum += item; } while (item < 5);

Answer 26

6

Question 27

Will the following program terminate? int balance = 10; while (true) { if (balance < 9) continue; balance = balance - 9; } A. Yes B. No

Answer 27

no

Question 28

What balance after the following code is executed? int balance = 10; while (balance >= 1) { if (balance < 9) continue; balance = balance - 9; } A. -1 B. 0 C. 1 D. 2 E. The loop does not end

Answer 28

E

Question 29

What is the number of iterations in the following loop? for (int i = 1; i < n; i++) { // iteration }

Answer 29

n-1

Question 30

What is the number of iterations in the following loop? for (int i = 1; i <= n; i++) { // iteration }

Answer 30

n

Question 31

Suppose the input for number is 9. What is the output from running the following program? import java.util.Scanner; public class Test { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.print("Enter an integer: "); int number = input.nextInt(); int i; boolean isPrime = true; for (i = 2; i < number && isPrime; i++) { if (number % i == 0) { isPrime = false; } } System.out.println("i is " + i); if (isPrime) System.out.println(number + " is prime"); else System.out.println(number + " is not prime"); } } A. i is 3 followed by 9 is prime B. i is 3 followed by 9 is not prime C. i is 4 followed by 9 is prime D. i is 4 followed by 9 is not prime

Answer 31

D. i is 4 followed by 9 is not prime

Question 32

Analyze the following code: import java.util.Scanner; public class Test { public static void main(String[] args) { int sum = 0; for (int i = 0; i < 100000; i++) { Scanner input = new Scanner(System.in); sum += input.nextInt(); } } } A. The program does not compile because the Scanner input = new Scanner(System.in); statement is inside the loop. B. The program compiles, but does not run because the Scanner input = new Scanner(System.in); statement is inside the loop. C. The program compiles and runs, but it is not efficient and unnecessary to execute the Scanner input = new Scanner(System.in); statement inside the loop. You should move the statement before the loop. D. The program compiles, but does not run because there is not prompting message for entering the input.

Answer 32

C. The program compiles and runs, but it is not efficient and unnecessary to execute the Scanner input = new Scanner(System.in); statement inside the loop. You should move the statement before the loop.