In Java, polymorphism is implemented using late binding. True False QUESTION 2 A

Question

In Java, polymorphism is implemented using late binding.

True

False

QUESTION 2

A subclass cannot directly access public members of a superclass.

True

False

QUESTION 3

GUI components are placed in a window called JFrame.

True

False

QUESTION 4

A polymorphic reference variable can refer to either an object of their own class or an object of the subclasses inherited from its class.

True

False

QUESTION 5

You can instantiate an object of an abstract class.

True

False

QUESTION 6

A subclass can directly access protected members of a superclass.

True

False

QUESTION 7

Suppose that the class Mystery is derived from the class Secret. Consider the following statements:

Secret secRef;
Mystery mysRef = new Mystery();
secRef = mysRef;

The value of the expression secRef instanceof Secret is true.

True

False

QUESTION 8

Inheritance lets you create new classes from existing classes.

True

False

QUESTION 9

An interface is a class that contains only abstract methods and/or named constants.

True

False

QUESTION 10

When we instantiate a subclass object, this object inherits the instance variables of the superclass, but the subclass object cannot directly access the private instance variables of the superclass.

True

False

QUESTION 11

In dynamic binding the method that gets executed is determined at the compile time not at execution time. On the other hand, in run-time binding the method that gets executed is determined at execution time not at compile time.

True

False

QUESTION 12

A subclass inherits all its data members from the superclass; it has none of its own.

True

False

QUESTION 13

Java uses late binding for methods that are private but not for methods that are marked final.

True

False

QUESTION 14

Using the mechanism of inheritance, every public member of the class Object can be overridden and/or invoked by every object of any class type.

True

False

QUESTION 15

In Java, a reference variable of a superclass type cannot point to an object of its subclass.

True

False

QUESTION 16

An abstract class can only contain abstract methods.

True

False

QUESTION 17

The class Object is directly or indirectly the superclass of every class in Java.

True

False

QUESTION 18

In Java, you can automatically make a reference variable of a subclass type point to an object of its superclass.

True

False

QUESTION 19

A subclass can have its own private data members, but a subclass cannot have its own constructors.

True

False

QUESTION 20

Suppose that the class Mystery is derived from the class Secret. The following statements are legal in Java.

Secret secRef;
Mystery mysRef = new Mystery();
secRef = mysRef;

True

False

QUESTION 21

Redefining a method of a superclass is also known as overloading a method.

True

False

QUESTION 22

The subclass can override public methods of a superclass.

True

False

QUESTION 23

Composition is a ‘‘is-a’’ relation.

True

False

QUESTION 24

The superclass inherits all its properties from the subclass.

True

False

QUESTION 25

An abstract method is a method that has only the heading with no body.

True

False

QUESTION 26

Every Java class (built-in or user-defined) automatically includes the method toString.

True

False

QUESTION 27

Composition is a “has-a” relation.

True

False

QUESTION 28

To override a public method of a superclass in a subclass, the corresponding method in the subclass must have the same name but a different number of parameters.

True

False

QUESTION 29

You can instantiate an object of a subclass of an abstract class, but only if the subclass gives the definitions of all the abstract methods of the superclass.

True

False

Inheritance implies an “is-a” relationship.

True

False

QUESTION 31

The private members of a superclass can be accessed by a subclass.

True

False

QUESTION 32

In Java, extends is a reserved word.

True

False

QUESTION 33

A call to the default constructor of a superclass must be the first statement in a constructor.

True

False

QUESTION 34

Inheritance implies an ‘‘has-a’’ relationship.

True

False

Explanation / Answer

Q1 - True, Late binding is a way to implement polymorphism.
Q2-False, the subcalss can directly access the public members of super classs, it cannot access the privte members directly.
Q3-True, all GUI components are placed in a frame which is known as JFRAME.
Q5-False. Object of abstract classes cannot be intantiated.
Q6- True, subclass can directly access the protected members of superclass.
Q7-False, instance is always created with a new keyword.
Q8-True Inheritance allows to reuse the code used in previous classes, so we can create new classes from the previous ones.
Q9-False.
Q10-True.
Q11- false the dynamic binding is another name of tun time binding the former is defination of static binding not dynamic binding.
Q12-False- inheritence extends the functionality of super class.

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