Question 1

What will be the output? <pre class="prettyprint"> 1. public interface InfA{ 2. protected String getName(); 3. } public class Test implements InfA{ public String getName(){ return "test-name"; } public static void main (String[] args){ Test t = new Test(); System.out.println(t.getName()); } } </pre>

A. test-name B. Compilation fails due to an error on lines 1 C. Compilation fails due to an error on lines 2 D. Compilation succeed but Runtime Exception

Question 2

Which of the following class definitions defines a legal abstract class?

A. class A { abstract void unfinished() { } } B. class A { abstract void unfinished(); } C. abstract class A { abstract void unfinished(); } D. public class abstract A { abstract void unfinished(); }

Question 3

Determine output of the following code. <pre class="prettyprint"> interface A { } class C { } class D extends C { } class B extends D implements A { } public class Test extends Thread{ public static void main(String[] args){ B b = new B(); if (b instanceof A) System.out.println("b is an instance of A"); if (b instanceof C) System.out.println("b is an instance of C"); } } </pre>

A. Nothing. B. b is an instance of A. C. b is an instance of C. D. b is an instance of A followed by b is an instance of C.

Question 4

What is the output for the below code ? <pre class="prettyprint"> interface A{ public void printValue(); } 1. public class Test{ 2. public static void main (String[] args){ 3. A a1 = new A(){ 4. public void printValue(){ 5. System.out.println("A"); 6. } 7. }; 8. a1.printValue(); 9. } 10. } </pre>

A. Compilation fails due to an error on line 3 B. A C. Compilation fails due to an error on line 8 D. null

Question 5

What happens if the following program is compiled and executed? <pre class="prettyprint"> interface MyInterface{ void display(); } interface MySubInterface extends MyInterface{ void display(); } public class Test implements MySubInterface{ public void display(){ System.out.print("Welcome to Examveda."); } public static void main(String args[]){ Test t = new Test(); t.display(); } } </pre>

A. The code will lead to a compilation error as declaration of the display method has been provided in two interface. B. The code will lead to a compilation error due to public modifier while declaring the display method. C. The code will compile and execute successfully showing the output Welcome to Examveda. D. The code will lead to a compilation error as the display method is not declared as abstract.

Question 6

<pre class="prettyprint"> interface Test{ int p = 10; //line 1 public int q = 20; //line 2 public static int r = 30; //line 3 public static final int s = 40; //line 4 } </pre> Which of the above line will give compilation error?

A. 1 B. 2 C. 3 D. None of these

Question 7

What will be the output when the following program is compiled and executed? <pre class="prettyprint"> abstract class TestAbstract{ String my_name; String myName(){ my_name = "Examveda"; return my_name; } abstract void display(); } public class Test extends TestAbstract{ void display(){ String n = myName(); System.out.print("My name is "+ n); } public static void main(String args[]){ Test t = new Test(); t.display(); } } </pre>

A. Program will compile and execute successfully and prints B. Compilation error as class can not be declared as abstract. C. Program compiles but leads to runtime exception. D. Compilation error occurs as the abstract class TestAbstract contains a non-abstract method.

Question 8

What will be the output? <pre class="prettyprint"> interface A{ public void method(); } class One{ public void method(){ System.out.println("Class One method"); } } class Two extends One implements A{ public void method(){ System.out.println("Class Two method"); } } public class Test extends Two{ public static void main(String[] args){ A a = new Two(); a.method(); } } </pre>

A. will print Class One method B. will print Class Two method C. compiles fine but print nothing D. Compilation Error

Question 9

Given the following piece of code: <pre class="prettyprint"> public class School{ public abstract double numberOfStudent(); } </pre> which of the following statements is true?

A. The keywords public and abstract cannot be used together. B. The method numberOfStudent() in class School must have a body. C. You must add a return statement in method numberOfStudent(). D. Class School must be defined abstract.

Question 10

Which two of the following are legal declarations for abstract classes and interfaces? 1. final abstract class Test {} 2. public static interface Test {} 3. final public class Test {} 4. protected abstract class Test {} 5. protected interface Test {} 6. abstract public class Test {}

A. 1 and 2 B. 2 and 4 C. 3 and 5 D. 3 and 6

Java Interfaces And Abstract Classes MCQ