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Oops Concepts In Java

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Oops concept in java

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Questions and Answers
  • 1. 
    The benefits of the Object Orientation are: ( choose two )
    • A. 

      Inheritance

    • B. 

      Flexibility

    • C. 

      Maintainability

    • D. 

      Polymorphism

  • 2. 
    • A. 

      Compile error

    • B. 

      2

    • C. 

      4

    • D. 

      No Output

  • 3. 
    HAS-A relationships are based on inheritance, rather than usage.  
    • A. 

      True

    • B. 

      False

  • 4. 
    • A. 

      By adding argument "int size" to the method book at line number 3.

    • B. 

      By removing argument '2' at line number 18.

    • C. 

      By creating object of "SuperHotel" subclass at line 17 & calling book(2) from it at line 18

    • D. 

      No correction needed.

  • 5. 
    Given below the sample code :   import java.io.IOException;   class Example7 { public float Twin(float x, float y) throws IOException { return 0; } }   class SubExample7 extends Example7 { float Twin(float x, float y) { return 0; } }     How can we correct above code ? (choose two)  
    • A. 

      No need for correction.

    • B. 

      By changing the method's argument name.

    • C. 

      By removing overridden method 's access specifier(i.e public).

    • D. 

      By adding access specifier 'public' to the overriding method.

  • 6. 
    In Java, the actual method executed is determined by the type of the object and not the type of the reference.  
    • A. 

      True

    • B. 

      False

  • 7. 
     The methods in class object are(choose four)  
    • A. 

      Clone

    • B. 

      Notify

    • C. 

      Concat

    • D. 

      Wait

    • E. 

      Equals

    • F. 

      Compare

  • 8. 
      Array or collection of superclass references can be used to access a mixture of superclass and subclass objects.  
    • A. 

      True

    • B. 

      False

  • 9. 
    • A. 

      By placing overriding method into subclass.

    • B. 

      By changing the name of the class.

    • C. 

      By replacing overloading from overriding.

    • D. 

      By changing the name of the arguments.

  • 10. 
    A class can inherit instance variables and methods from a more abstract superclass.
    • A. 

      True

    • B. 

      False

  • 11. 
    At run-time, a Java program is nothing more than objects ‘talking’ to ___________.
    • A. 

      Other objects

    • B. 

      Other metods

    • C. 

      Other classes

    • D. 

      Other binders

  • 12. 
    If you do not have access to the source code for a class, but you want to change the way a method of that class works, then could you use subclassing to do that that is to extend the “bad” class and override the method with your own better code?  
    • A. 

      True

    • B. 

      False

  • 13. 
       The relation between Car and Owner or BankAccount and Customer is example for  
    • A. 

      Aggregation

    • B. 

      Composition

    • C. 

      Association

    • D. 

      None

  • 14. 
    Aggregation is a special form of association.  
    • A. 

      True

    • B. 

      False

  • 15. 
     Subclassing polymorphism is sometimes called “true polymorphism”.
    • A. 

      True

    • B. 

      False

  • 16. 
     A method defined in a superclass is redefined in a subclass with an identical method signature is called___________.
    • A. 

      Method overloading

    • B. 

      Method overriding

    • C. 

      Dynamic binding

    • D. 

      Late binding

  • 17. 
    Consider the below code and choose the correct output. public class Main { public int a; public long b; public void test(long  b) { System.out.println("long b"); } public void test(int a) { System.out.println("int a"); } public static void main(String[] args) {                 Main e=new Main();         e.test(9*1000000000);               }   }  
    • A. 

      Int a

    • B. 

      Long b

    • C. 

      Long a

    • D. 

      Error

  • 18. 
      An interface cannot have an inner class.  
    • A. 

      True

    • B. 

      False

  • 19. 
    Polymorphism is one interface with __________.  
    • A. 

      Single method

    • B. 

      Multiple methods

    • C. 

      Multiple record

    • D. 

      Single record

  • 20. 
    Method overloading is done during _______.
    • A. 

      Runtime

    • B. 

      Dynamic binding

    • C. 

      Program compilation

    • D. 

      Late binding

  • 21. 
    Interfaces are fast as it requires extra indirection to find corresponding method in the actual class.  
    • A. 

      True

    • B. 

      False

  • 22. 
    Ad hoc polymorphism is ____________.
    • A. 

      Method Overloading

    • B. 

      Method Overriding

    • C. 

      Subclassing polymorphism

    • D. 

      Dynamic binding

  • 23. 
    The inheriting class cannot override the definition of existing methods by providing its own implementation.
    • A. 

      True

    • B. 

      False

  • 24. 
    The ability to make changes in your implementation code without breaking the code of others who use your code is a key benefit of _______________.  
    • A. 

      Extensibility

    • B. 

      Polymorphism

    • C. 

      Inheritance

    • D. 

      Encapsulation

  • 25. 
    Every class in Java is a subclass of class _____________.  
    • A. 

      Inheritance

    • B. 

      Object

    • C. 

      Exception

    • D. 

      ArrayList

  • 26. 
    Consider the code below and choose the correct option. class GameShape { public void displayShape() { System.out.println("displaying shape");    }    // more code }   class PlayerPiece extends GameShape { public void movePiece() { System.out.println("moving game piece");    }    // more code }   public class TestShapes {    public static void main (String[] args) {       PlayerPiece shape = new PlayerPiece();       shape.displayShape();       shape.movePiece();    } }  
    • A. 

      PlayingPiece class inherits the generic movePiece() method

    • B. 

      PlayingPiece class inherits the generic displayShape() method

    • C. 

      GameShape class inherits the generic displayShape() method

    • D. 

      GameShape class inherits the generic movePiece() method

  • 27. 
    The two most common reasons to use inheritance are( choose 2)
    • A. 

      To promote code reuse

    • B. 

      To use abstraction

    • C. 

      To use interface

    • D. 

      To use polymorphism

  • 28. 
    A class is not an object. But it is used to construct objects.  
    • A. 

      True

    • B. 

      False

  • 29. 
    Examples of class are( choose 3)  
    • A. 

      White

    • B. 

      Length

    • C. 

      Classroom

    • D. 

      Car

    • E. 

      Person

  • 30. 
    In OO, the concept of IS-A is based on  
    • A. 

      Class inheritance

    • B. 

      Interface implementation.

    • C. 

      Both

    • D. 

      None