JAVA Interfaces and Abstract Classes
Suppose A is an abstract class, B is a concrete subclass of A, and both A and B have a default constructor. Which of the following is correct?1. A a = new A();2. A a = new B();3. B b = new A();4. B b = new B();

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

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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
Runtime error
None of these

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

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

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

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