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); }}

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

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JAVA Interfaces and Abstract Classes
interface Base{ boolean m1 (); byte m2(short s);}which two code fragments will compile?1. interface Base2 implements Base {}2. abstract class Class2 extends Base { public boolean m1(){ return true; }}3. abstract class Class2 implements Base {}4. abstract class Class2 implements Base { public boolean m1(){ return (7 > 4); }}5. abstract class Class2 implements Base { protected boolean m1(){ return (5 > 7) }}

1 and 2
1 and 3
3 and 4
4 and 5
2 and 3

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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?

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

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

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

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

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