JAVA INTERFACES AND ABSTRACT CLASSES QUIZ

Which of the following declares an abstract method in an abstract Java class?

public void method() {}

public abstract void method() {}

public void abstract Method();

public abstract void method();

public abstract method();

TRUE ANSWER : ?
YOUR ANSWER : ?

What happens if the following program is compiled and executed?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(); }}

The code will lead to a compilation error as the display method is not declared as abstract.

None of these

The code will lead to a compilation error due to public modifier while declaring the display method.

The code will compile and execute successfully showing the output Welcome to Examians.

The code will lead to a compilation error as declaration of the display method has been provided in two interface.

TRUE ANSWER : ?
YOUR ANSWER : ?

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}Which of the above line will give compilation error?

3

1

4

None of these

2

TRUE ANSWER : ?
YOUR ANSWER : ?

In Java, declaring a class abstract is useful

To prevent developers from further extending the class.

When it doesn't make sense to have objects of that class.

When it makes sense to have objects of that class.

To force developers to extend the class not to use its capabilities.

When default implementations of some methods are not desirable.

TRUE ANSWER : ?
YOUR ANSWER : ?

Runnable is a _____ .

vaiable

method

class

abstract class

interface

TRUE ANSWER : ?
YOUR ANSWER : ?

Which of the following statements regarding abstract classes are true?

An abstract class can be used as a data type.

A subclass of a non-abstract superclass can be abstract.

A subclass can override a concrete method in a superclass to declare it abstract.

All of these

An abstract class can be extended.

TRUE ANSWER : ?
YOUR ANSWER : ?

interface Base{ boolean m1 (); byte m2(short s);}which two code fragments will compile?1. interface Base2 implements Base {}2. abstract class Class2 extends Base { public boolean m1(){ return true; }}3. abstract class Class2 implements Base {}4. abstract class Class2 implements Base { public boolean m1(){ return (7 > 4); }}5. abstract class Class2 implements Base { protected boolean m1(){ return (5 > 7) }}

2 and 3

1 and 2

3 and 4

4 and 5

1 and 3

TRUE ANSWER : ?
YOUR ANSWER : ?

What will be the output for the below code ?public interface TestInf{ int i =10;}public class Test{ public static void main(String... args){ TestInf.i=12; System.out.println(TestInf.i); }}

Compile with error

12

None of these

10

Runtime Exception

TRUE ANSWER : ?
YOUR ANSWER : ?

What will be the output?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();}}

None of these

compiles fine but print nothing

will print Class One method

Compilation Error

will print Class Two method

TRUE ANSWER : ?
YOUR ANSWER : ?

Given the following piece of code:public class School{ public abstract double numberOfStudent();}which of the following statements is true?

You must add a return statement in method numberOfStudent().

The keywords public and abstract cannot be used together.

Class School must be defined abstract.

The method numberOfStudent() in class School must have a body.

TRUE ANSWER : ?
YOUR ANSWER : ?