Exam 10: Inheritance and Polymorphism

What is the correct syntax for defining a new class Parakeet based on the superclass Bird?

Consider the following class definitions.public class BClass { Private int x; public void set(int a) { X = a; } public void print() { System.out.print(x); } }public class DClass extends BClass { Private int y; public void set(int a, int b) { //Postcondition: x = a; y = b; } Public void print(){ } }Which of the following correctly redefines the method print of DClass?(i) Public void print() { System.out.print(x + " " + y); }(ii) public void print() { Super.print(); System.out.print(" " + y); }

Based on the diagram in the accompanying figure, the method setDimension in the class Box ____ the method setDimension in the class Rectangle.

Suppose that the class Mystery is derived from the class Secret. Consider the following statements.Secret mySecret = new Secret(); Secret secRef;Mystery myMystery = new Mystery(); Mystery mysRef;secRef = myMystery;Which of the following statements is legal in Java? (i) mysRef = (Mystery) mySecret; (ii) mysRef = (Mystery) secRef;

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

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.

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

An abstract class ____.

Which of the following statements about the reference super is true?

Interfaces are defined using the reserved word interface and the reserved word class.

You must always use the reserved word super to use a method from the superclass in the subclass.

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

Consider the following class definitions.public class BClass { Private int x; Private double y; public void print() { } }public class DClass extends BClass { Private int a; Private int b; public void print() { } }Suppose that you have the following statement.DClass dObject = new DClass();How many instance variables does dObject have?

The method toString() is a public member of the class ____.

If a class is declared final, then no other class can be derived from this class.

Based on the diagram in the accompanying figure, which of the following members will Box NOT have direct access to?

In dynamic binding, the method that gets executed is determined at compile time, not at execution time.

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

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

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