Exam 10: Polymorphism

Which of the following GUI components would you use to allow the user to select between a range of numeric alternatives?

Which of the following is a listener class for a JSlider?

Why is it almost always a good idea to implement a toString( ) method when you define a class?

The fact that the System.out.println( ) method is able to handle such a wide variety of objects, and print them correctly, is an example of the polymorphic nature of the println( ) method.

Polymorphism is achieved by

The type of the reference, not the type of the object, is use to determine which version of a method is invoked in a polymorphic reference.

What does the following code do? Assume list is an array of int values, temp is some previously initialized int value, and c is an int initialized to 0. For (j=0; j < list.length; j++) If (list[j] < temp) c++;

Comparing the performance of selection sort and insertion sort, what can one say?

What is printed by the following code? public class Inherit { abstract class Speaker { abstract public void speak( ); } class Cat extends Speaker { public void speak( ) { System.out.println("Woof!"); } } class Dog extends Speaker { public void speak( ) { System.out.println("Meow!"); } } Inherit( ) { Speaker d = new Dog( ); Speaker c = new Cat( ); d.speak( ); c.speak( ); } public static void main(String[ ] args) { new Inherit( ); } }

Although insertion sort and selection sort have generally the same O(n²) performance, selection sort has an advantage of insertion sort. What is this advantage?