Java Multiple Choice Questions & Answers on Java.lang – Integer, Long & Character Wrappers for Freshers

1. Which of these is a wrapper for data type int?

a) Integer
b) Long
c) Byte
d) Double

Answer: a

2. Which of the following methods is a method of wrapper Integer for obtaining hash code for the invoking object?

a) int hash()
b) int hashcode()
c) int hashCode()
d) Integer hashcode()

Answer: c

3. Which of these is a super class of wrappers Long, Character & Integer?

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 is wrapper for simple data type char?

a) Float
b) Character
c) String
d) Integer

Answer: b

5. Which of the following is method of wrapper Integer for converting the value of an object into int?

a) bytevalue()
b) int intValue();
c) Bytevalue()
d) Byte Bytevalue().

Answer: b

6. Which of these methods is used to obtain value of invoking object as a long?

a) long value()
b) long longValue()
c) Long longvalue()
d) Long Longvalue()

Answer: b

Explanation: long longValue() is used to obtain value of invoking object as a long.

7. What is the output of this program?

1.     class Output {

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

3.             char a[] = {'a', '5', 'A', ' '};   

4.             System.out.print(Character.isDigit(a[0]) + " ");

5.             System.out.print(Character.isWhitespace(a[3]) + " ");

6.             System.out.print(Character.isUpperCase(a[2]));

7.         }

8.     }

a) true false true
b) false true true
c) true true false
d) false false false

Answer: b

Explanation: Character.isDigit(a[0]) checks for a[0], whether it is a digit or not, since a[0] i:e ‘a’ is a character false is returned. a[3] is a whitespace hence Character.isWhitespace(a[3]) returns a true. a[2] is an upper case letter i:e ‘A’ hence Character.isUpperCase(a[2]) returns true.

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.             Integer i = new Integer(257);  

4.             float x = i.floatValue();

5.             System.out.print(x);

6.         }

7.     }

a) 0
b) 1
c) 257
d) 257.0

Answer: d

10. What is the output of this program?

1.     class Output {

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

3.             Long i = new Long(256);  

4.             System.out.print(i.hashCode());

5.         }

6.     }

a) 256
b) 256.0
c) 256.00
d) 257.00

Answer: a