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.
Program compiles but leads to runtime exception.
None of these
Program will compile and execute successfully and prints
Compilation error as class can not be declared as abstract.

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JAVA Interfaces and Abstract Classes
In Java, declaring a class abstract is useful

When it makes sense to have objects of that class.
To force developers to extend the class not to use its capabilities.
To prevent developers from further extending the class.
When default implementations of some methods are not desirable.
When it doesn't make sense to have objects of that class.

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

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

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JAVA Interfaces and Abstract Classes
Determine output of the following code.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"); }}

b is an instance of
b is an instance of
b is an instance of A followed by b is an instance of
Nothing.

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