JAVA Interfaces and Abstract Classes
What will be the output for the below code ?public interface TestInf{ int i =10;}public class Test{ public static void main(String... args){ TestInf.i=12; System.out.println(TestInf.i); }}

10
Runtime Exception
12
None of these
Compile with error

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

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

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JAVA Interfaces and Abstract Classes
What will be the output?1. public interface InfA{2. protected String getName();3. }public class Test implements InfA{ public String getName(){ return "test-name"; } public static void main (String[] args){ Test t = new Test(); System.out.println(t.getName()); }}

Compilation fails due to an error on lines 2
test-name
Compilation succeed but Runtime Exception
Compilation fails due to an error on lines 1
None of these

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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().
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
In Java, declaring a class abstract is useful

When it makes sense to have objects of that class.
When it doesn't make sense to have objects of that class.
To prevent developers from further extending the 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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