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

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

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

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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(); }}

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

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

An abstract class can be used as a data type.
All of these
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.

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