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This module contains review questions and answers keyed to the module titled Java4090: The Comparator Interface, Part 1.

Revised: Wed Apr 06 23:12:11 CDT 2016

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Table of contents

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 Java4090: The Comparator Interface, 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 sorting order established by a Comparator must be the same as the natural order.

Answer 1

Question 2

True or False? A Comparator can be used to establish a sorting order for objects that don't have a natural ordering.

Answer 2

Question 3

True or False? The use of a Comparator is an alternative to the implementation of the Comparable interface.

Answer 3

Question 4

True or False? Comparable and Comparator are two different names for the same interface.

Answer 4

Question 5

What output is produced by the program shown in Listing 1 ?

  • Compiler Error
  • Runtime Error
  • 44321
  • 4321
  • 1234
  • 12344

Answer 5

Question 6

True or False? It is possible to instantiate a new TreeSet object using a constructor that receives an incoming reference to a Comparable object, in which case it is not necessary for the objects in the collection to implementthe Comparator interface.

Answer 6

Question 7

True or False? In Listing 1 , the constructor that is called to instantiate a new TreeSet object receives an incoming parameter of type Comparable .

Answer 7

Question 8

True or False? When the fillIt method shown in Listing 1 returns, the collection object referred to by ref will contain references to five objects of type MyClass with those objects encapsulating the values 4, 4, 3, 2, and 1.

Answer 8

Question 9

True or False? When the fillIt method shown in Listing 1 returns, the collection object referred to by ref will contain references to four objects of type MyClass with those objects encapsulating the values 1, 2, 3, and 4 sorted into the order shown.

Answer 9

Question 10

True or False? Given: the Comparator interface declares the two methods listed below:

  • public int compare(Object o1, Object o2)
  • public boolean equals(Object obj)

(Note that the Java documentation would replace the type Object with the generic type T. However, generics are beyond the scope of this course.)

A class that implements the Comparator interface must provide a concrete definition for the compare method but providing a concrete definition for the equals method is optional.

Answer 10

Question 11

True or False? The general behavior of the compare method of a Comparator object compares its two arguments for order and returns a negative integer, zero, or a positiveinteger as the first argument is less than, equal to, or greater than the second.

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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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