Revised: Wed Apr 06 22:21:03 CDT 2016
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Table of contents
- Preface
- Preview
- Discussion and sample code
- 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 Collectionsframework in particular.
This module explains why the elements stored in a TreeSet collection must be references to objects instantiated from a class that implements the Comparable interface. The module also briefly discusses an alternative approach using the Comparator interface.
The module shows you how to implement the Comparable interface for a new class definition, explains the "natural ordering of the elements" for a class, and discusses the "consistent with equals" requirement. Finally,the module shows you how to define a new class whose objects are eligible for inclusion in a TreeSet collection.
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 Comparable04.
- Listing 2 . The code with the problem.
- Listing 3 . The program named Comparable05.
- Listing 4 . Beginning of the class named MyClass.
- Listing 5 . The compareTo method.
- Listing 6 . The overridden equals method.
Preview
In this module, I will teach you why the elements stored in a TreeSet collection must be references to objects instantiated from a class thatimplements the Comparable interface. ( In a subsequent module, I will teach you about an alternative approach that makes use of the Comparator interface.)
I will provide an example of implementing the Comparable interface for a new class definition, and will teach you about the natural ordering of the elements for a class.