1. Which of these is a wrapper for data type int?
a) Integer
b) Long
c) Byte
d) Double
Explanation: Integer
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()
Explanation: int hashCode()
3. Which of these is a super class of wrappers Long, Character & Integer?
a) Long
b) Digits
c) Float
d) Number
Explanation: Number is an abstract class containing subclasses Double, Float, Byte, Short, Integer and Long.
4. Which of these is a wrapper for simple data type char
a) float
b) Character
c) String
d) Integer
Explanation: Character
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()
Explanation: int intValue();
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()
Explanation: long longValue() is used to obtain value of invoking object as a long.
7. What will be the output of the following Java program?
class Output
{
public static void main(String args[])
{
char a[] = {'a', '5', 'A', ' '};
System.out.print(Character.isDigit(a[0]) + " ");
System.out.print(Character.isWhitespace(a[3]) + " ");
System.out.print(Character.isUpperCase(a[2]));
}
}
a) true false true
b) false true true
c) true true false
d) false false false
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 uppercase letter i:e ‘A’ hence Character.isUpperCase(a[2]) returns true.
Output:
false true true
8. What will be the output of the following Java program?
class Output
{
public static void main(String args[])
{
Integer i = new Integer(257);
byte x = i.byteValue();
System.out.print(x);
}
}
a) 0
b) 1
c) 256
d) 257
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.
Output:
1
9. What will be the output of the following Java program?
class Output
{
public static void main(String args[])
{
Integer i = new Integer(257);
float x = i.floatValue();
System.out.print(x);
}
}
a) 0
b) 1
c) 257
d) 257.0
Explanation:
Output:
257.0
10. What will be the output of the following Java program?
class Output
{
public static void main(String args[])
{
Long i = new Long(256);
System.out.print(i.hashCode());
}
}
a) 256
b) 256.0
c) 256.00
d) 257.00
Explanation:
Output:
256