JAVA Interfaces and Abstract Classes
Which of the following is a correct interface?

abstract interface A { print(); }
abstract interface A { abstract void print(); { }}
interface A { void print(); }
interface A { void print() { } }

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JAVA Interfaces and Abstract Classes
Which of the following class definitions defines a legal abstract class?

abstract class A { abstract void unfinished(); }
class A { abstract void unfinished() { } }
public class abstract A { abstract void unfinished(); }
class A { abstract void unfinished(); }

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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(); }}

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

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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.
You must add a return statement in method numberOfStudent().
The method numberOfStudent() in class School must have a body.
Class School must be defined abstract.

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

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