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

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

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JAVA Interfaces and Abstract Classes
What is the output for the below code ?interface A{ public void printValue();}1. public class Test{2. public static void main (String[] args){3. A a1 = new A(){4. public void printValue(){5. System.out.println("A");6. }7. };8. a1.printValue();9. }10. }

None of these
A
null
Compilation fails due to an error on line 3
Compilation fails due to an error on line 8

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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); }}

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

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

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