Java Multiple Choice Questions & Answers on Java.lang package Byte & Short Wrappers for Freshers

1. Which of these methods of Byte wrapper can be used to obtain Byte object from a string?

a) toString()
b) getString()
c) decode()
d) encode()

Answer: c

Explanation: decode() methods returns a Byte object that contains the value specified by string.

2. Which of the following methods Byte wrapper return the value as a double?

a) doubleValue()
b) converDouble()
c) getDouble()
d) getDoubleValue()

Answer: a

Explanation: doubleValue() returns the value of invoking object as double.

3. Which of these is a super class of wrappers Byte and short wrappers?

a) Long
b) Digits
c) Float
d) Number

Answer: d

Explanation: Number is an abstract class containing subclasses Double, Float, Byte, Short, Integer and Long.

4. Which of these methods is not defined in both Byte and Short wrappers?

a) intValue()
b) isInfinite()
c) toString()
d) hashCode()

Answer: b

Explanation: isInfinite() methods is defined in Integer and Long Wrappers, returns true if specified value is an infinite value otherwise it returns false.

5. Which of these exceptions is thrown by compareTo() method defined in double wrapper?

a) IOException
b) SystemException
c) CastException
d) ClassCastException

Answer: d

Explanation: compareTo() methods compare the specified object to be double, if it is not then ClassCastException is thrown.

6. What is the output of this program?

1.     class Output {

2.         public static void main(String args[]) {

3.             Double i = new Double(257.5);  

4.             Double x = i.MAX_VALUE;

5.             System.out.print(x);

6.         }

7.     }

a) 0
b) 1.7976931348623157E308
c) 1.7976931348623157E30
d) None of the mentioned

Answer: b

Explanation: The super class of Double class defines a constant MAX_VALUE above which a number is considered to be infinity. MAX_VALUE is 1.7976931348623157E308.

7. What is the output of this program?

1.     class Output {

2.         public static void main(String args[]) {

3.             Double i = new Double(257.5);  

4.             Double x = i.MIN_VALUE;

5.             System.out.print(x);

6.         }

7.     }

a) 0
b) 4.9E-324
c) 1.7976931348623157E308
d) None of the mentioned

Answer: b

Explanation: The super class of Byte class defines a constant MIN_VALUE below which a number is considered to be negative infinity. MIN_VALUE is 4.9E-324.

8. What is the output of this program?

1.     class Output {

2.          public static void main(String args[]) {

3.              Integer i = new Integer(257);  

4.              byte x = i.byteValue();

5.              System.out.print(x);

6.         }

7.     }

a) 0
b) 1
c) 256
d) 257

Answer: b

Explanation: i.byteValue() method returns the value of wrapper i as a byte value. i is 257, range of byte is 256 therefore i value exceeds byte range by 1 hence 1 is returned and stored in x.

9. What is the output of this program?

1.     class Output {

2.         public static void main(String args[]) {

3.      Double i = new Double(257.578123456789);  

4.             float x = i.floatValue();

5.             System.out.print(x);

6.         }

7.     }

a) 0
b) 257.0
c) 257.57812
d) 257.578123456789

Answer: c

Explanation: floatValue() converts the value of wrapper i into float, since float can measure till 5 places after decimal hence 257.57812 is stored in floating point variable x.

10. What is the output of this program?

1.     class Output {

2.         public static void main(String args[]) {

3.             Double y = new Double(257.57812);

4.      Double i = new Double(257.578123456789);  

5.             try {

6.          int x = i.compareTo(y);

7.                 System.out.print(x);

8.             }

9.             catch(ClassCastException e) {

10.                 System.out.print("Exception");

11.             }

12.  }

13.     }

a) 0
b) 1
c) Exception
d) None of the mentioned

Answer: b

Explanation: i.compareTo() methods two double values, if they are equal then 0 is returned and if not equal then 1 is returned, here 257.57812 and 257.578123456789 are not equal hence 1 is returned and stored in x.