QUESTION 12 A subclass inherits all its data members from the superclass; it has

Question

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

QUESTION 12

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

False

Explanation: A subclass inherits all the members (fields, methods, and nested classes) from its superclass. But it can have its own data memmbers

QUESTION 13

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

False

Explanation: private, final and static members (methods and variables) use static binding while for virtual methods (In Java methods are virtual by default) binding is done during run time based upon run time object.

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.

False

Explanation: only methods are overidden, as class Object is base class for all, its public member can be invoked from ant class but only public member can be overidden.

QUESTION 15

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

False

Expanation: The reference variable of the Parent class is capable to hold its object reference as well as its child object reference.

QUESTION 16

An abstract class can only contain abstract methods.

False

Explanation: An abstract class is a class that is declared abstract—it may or may not include abstract methods.

QUESTION 17

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

True

QUESTION 18

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

False

Explanation: When a subclass extends a superclass, it can also have additional attributes
and methods not existing in the superclass.

QUESTION 19

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

False

Explanation: A subclass can have its own constructor

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

Explanation: The reference variable of the Parent class is capable to hold its object reference as well as its child object reference.

QUESTION 21

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

False

Explanation: Redefining a method of a superclass is also known as overriding a method.

QUESTION 22

The subclass can override public methods of a superclass.

True

QUESTION 23

Composition is a ‘‘is-a’’ relation.

False

Explanation: Composition is a "part-of" relationship.

QUESTION 24

The superclass inherits all its properties from the subclass.

False

Explanation: The subclass inherits all its properties from the superclass.

QUESTION 25

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

True

Explanation: An abstract method is a method that is declared without an implementation (without braces, and followed by a semicolon)

QUESTION 26

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

True

Explanation: Every class in java is child of Object class either directly or indirectly. Object class contains toString() method.

QUESTION 27

Composition is a “has-a” relation.

False

Explanation: Composition is a "part-of" relationship.

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.

False

Explanation: For overriding a superclass method, subclass must define method with same name and same paraeters.

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

Explanation: A class derived from the abstract class must implement all those methods that are declared as abstract in the parent class.

QUESTION 30

Inheritance implies an “is-a” relationship.

True

QUESTION 31

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

False

Explanation: private members of a superclass can not be accessed by a subclass

QUESTION 32

In Java, extends is a reserved word.

True

QUESTION 33

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

False

Explanation: If the subclass constructor does not specify which superclass constructor to invoke then the compiler will automatically call the accessible no-args constructor in the superclass.

QUESTION 34

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

False

Explanation: Association is a “has-a” type relationship

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