JAVA Interfaces and Abstract Classes
Suppose A is an abstract class, B is a concrete subclass of A, and both A and B have a default constructor. Which of the following is correct?1. A a = new A();2. A a = new B();3. B b = new A();4. B b = new B();

1 and 2
1 and 3
2 and 4
2 and 3
3 and 4

ANSWER DOWNLOAD EXAMIANS APP

JAVA Interfaces and Abstract Classes
Which of the following statements regarding abstract classes are true?

A subclass can override a concrete method in a superclass to declare it abstract.
A subclass of a non-abstract superclass can be abstract.
All of these
An abstract class can be used as a data type.
An abstract class can be extended.

ANSWER DOWNLOAD EXAMIANS APP

JAVA Interfaces and Abstract Classes
Which of the following class definitions defines a legal abstract class?

public class abstract A { abstract void unfinished(); }
abstract class A { abstract void unfinished(); }
class A { abstract void unfinished() { } }
class A { abstract void unfinished(); }

ANSWER DOWNLOAD EXAMIANS APP

JAVA Interfaces and Abstract Classes
What will be the output when the following program is compiled and executed?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(); }}

Compilation error occurs as the abstract class TestAbstract contains a non-abstract method.
Compilation error as class can not be declared as abstract.
None of these
Program compiles but leads to runtime exception.
Program will compile and execute successfully and prints

ANSWER DOWNLOAD EXAMIANS APP
MORE MCQ ON JAVA Interfaces and Abstract Classes