Questions and answers for exam Preparation

MCQs

Total Questions : 65 | Page 2 of 7 pages

Question 11. What will be the output for the below code ?
class A{
public void printValue(){
System.out.println("A");
}
}
class B extends A{
public void printValue(){
System.out.println("B");
}
}
1. public class Test{
2. public static void main(String... args){
3. A b = new B();
4. newValue(b);
5. }
6. public static void newValue(A a){
7. if(a instanceof B){
8. ((B)a).printValue();
9. }
10. }
11. }

A
B
Compilation fails with an error at line 4
Compilation fails with an error at line 8
None of these

Discuss Question

Answer: Option B. -> B

Question 12. Determine output:
public class Test{
static int i = 5;
public static void main(String... args){
System.out.println(i++);
System.out.println(i);
System.out.println(++i);
System.out.println(++i+i++);
}
}

6 6 6 16
6 7 6 16
5 6 7 16
5 6 6 16
None of these

Discuss Question

Answer: Option C. -> 5 6 7 16

Question 13.

Which two are equal?

32/4
(8 >> 2) << 4
2^5
128 >>> 2
2 >> 5

1 and 2
2 and 4
1 and 3
2 and 3

Discuss Question

Answer: Option B. -> 2 and 4

(2) and (4) are correct. (2) and (4) both evaluate to 32. (2) is shifting bits right then left

using the signed bit shifters >>and <<. (4) is shifting bits using the unsigned operator

>>>, but since the beginning number is positive the sign is maintained.

(1) evaluates to 8, (3) looks like 2 to the 5^th power, but ^ is the Exclusive OR operator

so (3) evaluates to 7. (5) evaluates to 0 (2 >> 5 is not 2 to the 5^th).

Question 14.
import java.awt.Button;
class CompareReference
{
public static void main(String [] args)
{
float f = 42.0f;
float [] f1 = new float[2];
float [] f2 = new float[2];
float [] f3 = f1;
long x = 42;
f1[0] = 42.0f;
}
}

which three statements are true?

1. f1 == f2

2. f1 == f3

3. f2 == f1[1]

4. x == f1[0]

f == f1[0]

1, 2 and 3
2, 4 and 5
3, 4 and 5
1, 4 and 5

Discuss Question

Answer: Option B. -> 2, 4 and 5

(2) is correct because the reference variables f1 and f3 refer to the same array object.

(4) is correct because it is legal to compare integer and floating-point types.

(5) is correct because it is legal to compare a variable with an array element.

(3) is incorrect because f2 is an array object and f1[1] is an array element.

Question 15.

Which two statements are equivalent?

3/2
3<2
3*4
3<<2

1 and 2
2 and 3
3 and 4
1 and 4

Discuss Question

Answer: Option C. -> 3 and 4

(1) is wrong. 3/2 = 1 (integer arithmetic).

(2) is wrong. 3 < 2 = false.

(3) is correct. 3 * 4 = 12.

(4) is correct. 3 <<2= 12. In binary 3 is 11, now shift the bits two places to the left and we get 1100 which is 12 in binary (3*2*2).

Question 16.

Which of the following are legal lines of code?

int w = (int)888.8;
byte x = (byte)1000L;
long y = (byte)100;
byte z = (byte)100L;

1 and 2
2 and 3
3 and 4
All statements are correct.

Discuss Question

Answer: Option D. -> All statements are correct.

Statements (1), (2), (3), and (4) are correct. (1) is correct because when a floating-

point number (a double in this case) is cast to an int, it simply loses the digits after

the decimal.

(2) and (4) are correct because a long can be cast into a byte. If the long is over 127,

it loses its most significant (leftmost) bits.

(3) actually works, even though a cast is not necessary, because a long can store a byte.

Question 17.

Which two statements are equivalent?

16*4
16>>2
16/2^2
16>>>2

1 and 2
2 and 4
3 and 4
1 and 3

Discuss Question

Answer: Option B. -> 2 and 4

(2) is correct. 16 >> 2 = 4

(4) is correct. 16 >>> 2 = 4

(1) is wrong. 16 * 4 = 64

(3) is wrong. 16/2 ^ 2 = 10

Question 18.
import java.awt.*;
class Ticker extends Component
{
public static void main (String [] args)
{
Ticker t = new Ticker();
/* Missing Statements ? */
}
}

which two of the following statements, inserted independently, could legally be inserted into missing section of this code?

1. boolean test = (Component instanceof t);

2. boolean test = (t instanceof Ticker);

3. boolean test = t.instanceof(Ticker);

4. boolean test = (t instanceof Component);

1 and 4
2 and 3
1 and 3
2 and 4

Discuss Question

Answer: Option D. -> 2 and 4

(2) is correct because class type Ticker is part of the class hierarchy of t; therefore it is

a legal use of the instanceof operator. (4) is also correct because Component is part of

the hierarchy of t, because Ticker extends Component.

(1) is incorrect because the syntax is wrong. A variable (or null) always appears before

the instanceof operator, and a type appears after it. (3) is incorrect because the statement

is used as a method (t.instanceof(Ticker);), which is illegal.

Question 19.

What will be the output of the program?

public class Test
{
public static void leftshift(int i, int j)
{
i

Discuss Question

Answer: Option B. -> 4

Java only ever passes arguments to a method by value (i.e. a copy of the variable)

and never by reference. Therefore the value of the variable i remains unchanged in

the main method.

If you are clever you will spot that 16 is 4 multiplied by 2 twice, (4 * 2 * 2) = 16. If you

had 16 left shifted by three bits then 16 * 2 * 2 * 2 = 128. If you had 128 right shifted by

2 bits then 128 / 2 / 2 = 32. Keeping these points in mind, you don't have to go converting

to binary to do the left and right bit shifts.

Question 20.

What will be the output of the program?

class Two
{
byte x;
}
class PassO
{
public static void main(String [] args)
{
PassO p = new PassO();
p.start();
}
void start()
{
Two t = new Two();
System.out.print(t.x + " ");
Two t2 = fix(t);
System.out.println(t.x + " " + t2.x);
}
Two fix(Two tt)
{
tt.x = 42;
return tt;
}
}