Exam 10: Polymorphism

Consider this statement: If you declare a (polymorphic) reference variable, v, to be of type Object, by saying: Object v; then v can refer to any kind of object without restriction. If "object" means an instance of the Object class, is this statement True? Why or why not? If "object" means any kind of Java data, is this statement True? Why or why not?

What is printed? Public class Inherit { Class Figure { Void display( ) { System.out.println("Figure"); } } Class Rectangle extends Figure { Void display( ) { System.out.println("Rectangle"); } } Class Box extends Figure { Void display( ) { System.out.println("Box"); } } Inherit( ) { Figure f = new Figure( ); Rectangle r = new Rectangle( ); Box b = new Box( ); f.display( ); f = r; f.display( ); F = b; f.display( ); } Public static void main(String[ ] args) { New Inherit( ); } }

Which of the following GUI components would you use to display a list of options so that the user could select between the entries in the list?

A polymorphic reference can refer to different types of objects over time.

What is the efficiency of binary search?

What is printed? Public class Inherit { Abstract class Figure { Void display( ) { System.out.println("Figure"); } } Abstract class Rectangle extends Figure { } Class Box extends Rectangle { Void display( ) { System.out.println("Rectangle"); } } Inherit( ) { Figure f = (Figure) new Box( ); f.display( ); Rectangle r = (Rectangle) f; r.display( ); } Public static void main(String[ ] args) { New Inherit( ); } }

We compare sorting algorithms by examining

Consider the code shown below. It contains a syntax error, preventing successful compilation and execution. What is the error? public class Inherit { class Figure { void display( ) { System.out.println("Figure"); } } class Rectangle extends Figure { final void display( ) { System.out.println("Rectangle"); } } class Box extends Rectangle { void display( ) { System.out.println("Box"); } } Inherit( ) { Figure f = new Figure( ); Rectangle r = new Rectangle( ); Box b = new Box( ); f.display( ); r.display( ); b.display( ); } public static void main(String[ ] args) { new Inherit( ); } }

Which of these methods will sort an array of floats into ascending order?

What kind of performance can you expect if you perform linear search on a sorted array?