Java Programming Multiple Choice Questions - Interfaces
This section focuses on the "Interfaces" in Java programming. These Multiple Choice Questions (MCQ) should be practiced to improve the Java programming skills required for various interviews (campus interviews, walk-in interviews, company interviews), placements and other competitive examinations.
1. Which of these keywords is used to define interfaces in Java?
A. interface
B. Interface
C. intf
D. Intf
View Answer
Ans : A
Explanation: interface keywords is used to define interfaces in Java.
2. A java interface can contain _______.
A. Abstract methods(unimplemented) and implemented methods both
B. public Abstract methods
C. public static Final Variables only
D. public static Final Variables and abstract methods both
View Answer
Ans : D
Explanation: An interface can have both final variables and abstract methods.
3. Which of these access specifiers can be used for an interface?
A. Public
B. private
C. Protected
D. All of the mentioned
View Answer
Ans : A
Explanation: Access specifier of interface is either public or no specifier. When no access specifier is used then default access specifier is used due to which interface is available only to other members of the package in which it is declared, when declared public it can be used by any code.
4. Which of the following is a correct interface?
A. abstract interface A { abstract void print(); { }}
B. abstract interface A { print(); }
C. interface A { void print() { } }
D. interface A { void print(); }
View Answer
Ans : D
Explanation: No explanation.
5. Which of the following classes directly implement Set interface?
A. Vector
B. HashSet
C. HashTable
D. LinkedList
View Answer
Ans : B
Explanation: HashSet classes directly implement Set interface
6. Which of these can be used to fully abstract a class from its implementation?
A. Objects
B. Packages
C. Interfaces
D. None of the Mentioned
View Answer
Ans : C
Explanation: None.
7. What is the output of this program?
interface calculate
{
void cal(int item);
}
class display implements calculate
{
int x;
public void cal(int item)
{
x = item * item;
}
}
class Main
{
public static void main(String args[])
{
display arr = new display();
arr.x = 0;
arr.cal(2);
System.out.print(arr.x);
}
}
A. 0
B. 2
C. 4
D. None of the mentioned
View Answer
Ans : C
Explanation: None.
Output:
$ javac interfaces.java
$ java interfaces
4
8. All methods must be implemented of an interface.
A. TRUE
B. FALSE
C. Can be true or false
D. can not say
View Answer
Ans : A
Explanation: Concrete classes must implement all methods in an interface. Through interface multiple inheritance is possible.
9. What type of variable can be defined in an interface?
A. public static
B. private final
C. public final
D. static final
View Answer
Ans : D
Explanation: variable defined in an interface is implicitly final and static. They are usually written in capital letters.
10. What does an interface contain?
A. Method definition
B. Method declaration
C. Method declaration and definition
D. Method name
View Answer
Ans : B
Explanation: Interface contains the only declaration of the method.
Also check :
Discussion