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?

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

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JAVA Interfaces and Abstract Classes
What will happen after compiling this program code?abstract class MyClass{ //line 1 private int a, b; public void call(int a, int b){ this.a = a; this.b = b; System.out.print(a+b); }}public class Test{ public static void main(String args[]){ MyClass m = new MyClass(); //line 2 m.call(12,25); }}

Compilation error due to line 2
Successful run and print 37
Compilation error due to line 1
None of these
Runtime error

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JAVA Interfaces and Abstract Classes
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 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.
None of these
The code will lead to a compilation error as the display method is not declared as abstract.
The code will lead to a compilation error due to public modifier while declaring the display method.

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

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

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