Oops Concepts In Java

30 Questions  I  By Srividya123
 oops concept in java

  
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1.  Polymorphism is one interface with __________.  
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B.
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2.  In OO, the concept of IS-A is based on  
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D.
3.  Every class in Java is a subclass of class _____________.  
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D.
4.  Method overloading is done during _______.
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5.  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();    } }  
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6.  Given below the sample code :   1   class Hotel { 2   public int bookings; 3   public void book() { 4   bookings++; 5   } 6   } 7   public class SuperHotel extends Hotel { 8   public void book() { 9   bookings--; 10  } 11  public void book(int size) { 12  book(); 13  super.book(); 14  bookings += size; 15  } 16  public static void main(String args[]) { 17  Hotel hotel = new Hotel(); 18  hotel.book(2); 19  System.out.print(hotel.bookings); 20  }}   How can we correct the above code ? (choose all that apply)  
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7.   Subclassing polymorphism is sometimes called “true polymorphism”.
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8.  HAS-A relationships are based on inheritance, rather than usage.  
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9.  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?  
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10.  Given below the sample code :   class Hotel { public int bookings=2; public void book() { bookings++; } }   public class SuperHotel extends Hotel { public void book() { bookings--; }   public void book(int size) { book(); super.book(); bookings += size; }   public static void main(String args[]) { SuperHotel Shotel = new SuperHotel(); Shotel.book(2); System.out.print(Shotel.bookings); } }   Find the output of the following code :  
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11.  At run-time, a Java program is nothing more than objects ‘talking’ to ___________.
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12.  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)  
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13.  In Java, the actual method executed is determined by the type of the object and not the type of the reference.  
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14.  The inheriting class cannot override the definition of existing methods by providing its own implementation.
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15.  Examples of class are( choose 3)  
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16.     The relation between Car and Owner or BankAccount and Customer is example for  
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17.    Array or collection of superclass references can be used to access a mixture of superclass and subclass objects.  
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18.  Aggregation is a special form of association.  
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19.  The benefits of the Object Orientation are: ( choose two )
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20.  Ad hoc polymorphism is ____________.
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21.    An interface cannot have an inner class.  
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22.  Given the following sample code:   public class Example5{       public float Twin(float a, float b) {...         } public float Twin(float a1, float b1) { ...}           }   How can we correct the above code ?(choose two)  
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23.  The ability to make changes in your implementation code without breaking the code of others who use your code is a key benefit of _______________.  
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24.   A method defined in a superclass is redefined in a subclass with an identical method signature is called___________.
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25.  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);               }   }  
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26.  Interfaces are fast as it requires extra indirection to find corresponding method in the actual class.  
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27.  A class is not an object. But it is used to construct objects.  
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28.  A class can inherit instance variables and methods from a more abstract superclass.
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29.  The two most common reasons to use inheritance are( choose 2)
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30.   The methods in class object are(choose four)  
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