4.29 Java4150r: review

Revised: Fri Apr 08 12:48:52 CDT 2016

This page is included in the following Books:

• ITSE 2321 - Object-Oriented Programming (Java)
• Object-Oriented Programming (OOP) with Java

Table of contents

• Preface
• Questions
  • 1 , 2 , 3 , 4 , 5 , 6
• Figures
• Listings
• Answers
• Complete program listing
• Miscellaneous

Preface

This module is one in a collection of modules on Java Collections designed for teaching ITSE2321 - Object-Oriented Programming (Java) at Austin Community College in Austin, TX.

This module contains review questions and answers keyed to the module titled Java4150: The toArray Method, Part 1 .

Once you study that module, you should be able to answer the review questions in this module.

The questions and the answers in this module are connected by hyperlinks to make it easy for you to navigate from the question to the answer and back again.

Questions

Question 1 .

True or False? The Collection interface declares the following two versions of the toArray method (with generics syntax omitted because generics is beyond the scope of this course) .

public Object[] toArray()

public Object[] toArray(Object[]a)

Answer 1

Question 2

Write down the output produced by the program in Listing 1 .

Answer 2

Question 3

True or False? When the toArray method is used to produce an array containing the contents of a collection, modifying the contents of thearray will also modify the contents of the underlying collection.

Answer 3

Question 4

True or False? When the toArray method is used to produce an array containing the contents of a collection, the array ends up containingreferences to copies of the objects referred to by the elements of the collection.

Answer 4

Question 5

True or False? In Java, it is not possible to have two or more references to the same object.

Answer 5

Question 6

True or False? When the toArray method is used to produce anarray containing the contents of a collection, if you use a reference stored in the array to modify the state of the object to which it refers, thatmodification is made to an object that is also referred to by an element in the collection. The array and the collection contain references to the same objects.

Answer 6

Figures

• Figure 1 . Answer 2.

Listings

• Listing 1 . ToArray01.java.

What is the meaning of the following two images?

These images were inserted here simply to insert some space between the questions and the answers to keep them from being visible on the screen at thesame time.

This image was also inserted for the purpose of inserting space between the questions and the answers.

Answers

Answer 6

True.

Back to Question 6

Answer 5

False. In Java, it is entirely possible to have two or more references to the same object.

Back to Question 5

Answer 4

False. When the toArray method is used to produce an array containing the contents of a collection, the collection and the array end upcontaining copies of references to the same underlying objects.

Back to Question 4

Answer 3

False. According to Oracle,