4.12 Java4070: the comparable interface, part 1

Revised: Wed Apr 06 13:05:35 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
  • Viewing tip
    • Listings
• Preview
  • Generics
  • Specialization
  • To cast, or not to cast
  • Comparable interface not required for a List
• Discussion and sample code
  • We will begin with a quiz
    • What caused the compiler error?
    • Implements Collection and List
    • Specialization
  • Modified program
    • The corrected code
    • Casting to type List
  • The List contract for the add method
    • Controlling the locations of the elements
    • Add method actually does an insert
  • The Vector class
  • More on the List contract
    • Duplicates are allowed in a List
  • One more sample program
    • No need to cast to type List
  • What happened to the Comparable interface?
    • Comparable interface is not required for a List
    • No requirement to compare
    • Comparison is required for a SortedSet
• Run the program
• Summary
• What's next?
• Miscellaneous

Preface

This module is one of a series of modules designed to teach you about Object-Oriented Programming (OOP) in general and the Java Collections Framework in particular.

This is also the first module in a sub-collection on the Comparable interface. The purpose of the modules in this sub-collection is to teach you about the interactions between the Comparable interface and the Collections Framework, particularly with respect to the Set , SortedSet , and SortedMap interfaces of the Collections Framework.

This module also explains the (lack of) interaction between the Comparable interface and the Java Collections Framework with respect to collections of type List .

In addition to studying these modules, I strongly recommend that you study the Collections Trail in Oracle's Java Tutorials . The modules in this collection are intended to supplement and not to replace those tutorials.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the listings while you are reading about them.

Listings

• Listing 1 . The program named Comparable01.
• Listing 2 . The code with the problem.
• Listing 3 . The program named Comparable02.
• Listing 4 . The corrected code.
• Listing 5 . Display using an iterator.
• Listing 6 . The program named Comparable03.
• Listing 7 . No need to cast to type List.

Preview

In this module, I will begin discussing the interaction between the Comparable interface and the Collections Framework.

Generics

The code in this module is written with no thought given to Generics . As a result, if you copy and compile this code, you will probably get a warning about unchecked or unsafe operations .