40 computer science quiz about java

Exam

Name___________________________________

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

1) Analyze the following program fragment:

int x; double d = 1.5;

switch (d) { case 1.0: x = 1; case 1.5: x = 2; case 2.0: x = 3; }

1)

A) The switch control variable cannot be double. B) The program has a compile error because the required break statement is missing in the

switch statement. C) The program has a compile error because the required default case is missing in the switch

statement. D) No errors.

2) Analyze the following code:

boolean even = false; if (even = true) { System.out.println("It is even!"); }

2)

A) The program runs fine, but displays nothing. B) The program runs fine and displays It is even!. C) The program has a runtime error. D) The program has a compile error.

3) What is the printout of the following switch statement? char ch = 'a'; switch (ch) { case 'a': case 'A': System.out.print(ch); break; case 'b': case 'B': System.out.print(ch); break; case 'c': case 'C': System.out.print(ch); break; case 'd': case 'D': System.out.print(ch); }

3)

A) abc B) abcd C) ab D) aa E) a

1

4) The order of the precedence (from high to low) of the operators +, *, &&, ||, & is: 4) A) *, +, &, &&, || B) *, +, &&, ||, & C) &&, ||, &, *, + D) &, ||, &&, *, + E) *, +, &, ||, &&

5) The statement System.out.printf("%10s", 123456) outputs ________. (Note: * represents a space) 5) A) ****123456 B) 12345***** C) 123456**** D) 23456*****

6) The following code displays ________.

double temperature = 50;

if (temperature >= 100) System.out.println("too hot"); else if (temperature <= 40) System.out.println("too cold"); else System.out.println("just right");

6)

A) too cold B) too hot C) too hot too cold just right D) just right

7) Which of the following code displays the area of a circle if the radius is positive? 7) A) if (radius >= 0) System.out.println(radius * radius * 3.14159); B) if (radius != 0) System.out.println(radius * radius * 3.14159); C) if (radius > 0) System.out.println(radius * radius * 3.14159); D) if (radius <= 0) System.out.println(radius * radius * 3.14159);

8) ________ is the code with natural language mixed with Java code. 8) A) A flowchart diagram B) Java program C) Pseudocode D) A Java statement

9) Analyze the following code:

if (x < 100) && (x > 10) System.out.println("x is between 10 and 100");

9)

A) The statement compiles fine. B) The statement has compile errors because (x<100) & (x > 10) must be enclosed inside

parentheses and the println(…) statement must be put inside a block. C) The statement compiles fine, but has a runtime error. D) The statement has compile errors because (x<100) & (x > 10) must be enclosed inside

parentheses.

10) In Java, the word true is ________. 10) A) same as value 1 B) same as value 0 C) a Boolean literal D) a Java keyword

2

11) How many times will the following code print "Welcome to Java"?

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

11)

A) 11 B) 0 C) 8 D) 9 E) 10

12) 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);

12)

A) 5 B) 7 C) 6 D) 8

13) What is i after the following for loop?

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

13)

A) 9 B) 11 C) 10 D) undefined

14) How many times will the following code print "Welcome to Java"?

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

14)

A) 11 B) 8 C) 0 D) 10 E) 9

15) How many times will the following code print "Welcome to Java"?

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

15)

A) 0 B) 10 C) 9 D) 11 E) 8

3

16) What is the number of iterations in the following loop:

for (int i = 1; i < n; i++) { // iteration }

16)

A) 2*n B) n C) n + 1 D) n - 1

17) Analyze the following fragment:

double sum = 0; double d = 0; while (d != 10.0) { d += 0.1; sum += sum + d; }

17)

A) The program never stops because d is always 0.1 inside the loop. B) After the loop, sum is 0 + 0.1 + 0.2 + 0.3 + ... + 1.9 C) The program does not compile because sum and d are declared double, but assigned with

integer value 0. D) The program may not stop because of the phenomenon referred to as numerical inaccuracy

for operating with floating-point numbers.

18) What is Math.rint(3.5)? 18) A) 3.0 B) 5.0 C) 4.0 D) 3 E) 4

19) Which of the following should be declared as a void method? 19) A) Write a method that checks whether current second is an integer from 1 to 100. B) Write a method that prints integers from 1 to 100. C) Write a method that converts an uppercase letter to lowercase. D) Write a method that returns a random integer from 1 to 100.

20) Given the following method

static void nPrint(String message, int n) { while (n > 0) { System.out.print(message); n--; } }

What is k after invoking nPrint("A message", k)?

int k = 2; nPrint("A message", k);

20)

A) 2 B) 0 C) 1 D) 3

21) What is Math.ceil(3.6)? 21) A) 3 B) 3.0 C) 4.0 D) 5.0

4

22) ________ is to implement one method in the structure chart at a time from the top to the bottom. 22) A) Bottom-up and top-down approach B) Top-down approach C) Stepwise refinement D) Bottom-up approach

23) What is the output of the following program?

import java.util.Date;

public class Test { public static void main(String[ ] args) { Date date = new Date(1234567); m1(date); System.out.print(date.getTime() + " ");

m2(date); System.out.println(date.getTime()); }

public static void m1(Date date) { date = new Date(7654321); }

public static void m2(Date date) { date.setTime(7654321); } }

23)

A) 7654321 1234567 B) 1234567 7654321 C) 1234567 1234567 D) 7654321 7654321

24) Which of the following statement is most accurate? (Choose all that apply.) 24) A) An object may contain other objects. B) A reference variable refers to an object. C) An object may contain the references of other objects. D) A reference variable is an object.

25) How many JFrame objects can you create and how many can you display? 25) A) three B) one C) two D) unlimited

26) An object is an instance of a ________. 26) A) data B) class C) method D) program

5

27) Analyze the following code fragments that assign a boolean value to the variable even.

Code 1: if (number % 2 == 0) even = true; else even = false;

Code 2: even = (number % 2 == 0) ? true: false;

Code 3: even = number % 2 == 0;

27)

A) Code 3 has a compile error, because you attempt to assign number to even. B) All three are correct, but Code 2 is preferred. C) All three are correct, but Code 1 is preferred. D) Code 2 has a compile error, because you cannot have true and false literals in the conditional

expression. E) All three are correct, but Code 3 is preferred.

28) What is the printout of the following switch statement?

char ch = 'b';

switch (ch) { case 'a': System.out.print(ch); case 'b': System.out.print(ch); case 'c': System.out.print(ch); case 'd': System.out.print(ch); }

28)

A) bcd B) bbb C) bb D) abcd E) b

29) Suppose x=10 and y=10. What is x after evaluating the expression (y > 10) && (x-- > 10)? 29) A) 11 B) 9 C) 10

30) To add 0.01 + 0.02 + ... + 1.00, what order should you use to add the numbers to get better accuracy? 30) A) add 1.00, 0.99, 0.98, ..., 0.02, 0.01 in this order to a sum variable whose initial value is 0. B) add 0.01, 0.02, ..., 1.00 in this order to a sum variable whose initial value is 0.

31) How many times are the following loops executed?

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

31)

A) 100 B) 10 C) 20 D) 45

6

32) Analyze the following code.

public class Test { public static void main(String[ ] args) { System.out.println(m(2)); }

public static int m(int num) { return num; }

public static void m(int num) { System.out.println(num); } }

32)

A) The program runs and prints 2 once. B) The program runs and prints 2 twice. C) The program has a compile error because the two methods m have the same signature. D) The program has a compile error because the second m method is defined, but not invoked in

the main method.

33) Which of the following is the best for generating random integer 0 or 1? 33) A) (int)Math.random() B) (int)(Math.random() + 0.2) C) (int)(Math.random() + 0.8) D) (int)Math.random() + 1 E) (int)(Math.random() + 0.5)

34) Variables that are shared by every instances of a class are ________. 34) A) private variables B) class variables C) instance variables D) public variables

35) Which of the following operators are right-associative? 35) A) + B) % C) * D) = E) &&

36) What is the number of iterations in the following loop:

for (int i = 1; i <= n; i++) { // iteration }

36)

A) n B) n + 1 C) n - 1 D) 2*n

37) What is Math.rint(3.6)? 37) A) 4.0 B) 3.0 C) 5.0 D) 3

7

38) What code may be filled in the blank without causing syntax or runtime errors:

public class Test { java.util.Date date;

public static void main(String[ ] args) { Test test = new Test(); System.out.println(________); } }

38)

A) test.date B) date.toString() C) test.date.toString() D) date

39) Suppose x=10 and y=10 what is x after evaluating the expression (y >= 10) || (x-- > 10)? 39) A) 11 B) 9 C) 10

40) 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);

40)

A) 8 B) 0 C) 9 D) 10 E) 11

8