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Baldwin shows you that all concrete implementations in the Collection hierarchy implement a sub-interface of the Collection interface. A Set object cannot contain duplicate elements, but a List object can contain duplicate elements. Ordered collections are not the same as sorted collections. Specialized stipulations are placed on interfaces as you progress down the interface inheritance hierarchy of the Java Collections Framework.

Revised: Wed Apr 06 09:47:48 CDT 2016

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Table of contents

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.

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.

Preview

You learned in earlier modules that the Java Collections Framework defines eight core interfaces, in two distinct trees.One of the trees, which consists of six interfaces, is rooted in the interface named Collection . The other tree, which consists of two interfaces, isrooted in the interface named Map .

You learned the names and the inheritance structure of those interfaces. You also learned about theirpurpose. You saw how the interfaces declare polymorphic methods that apply to implementations of the interfaces, and you learned about the optional methods ofthe Collection interface and the Map interface.

In this module you will learn that all of the implementations of the interfaces on the Collection side of the Java Collections Framework (the Collection hierarchy) implement one of the sub-interfaces of the Collection interface. (A similar discussion regarding the Map side of the Java Collections framework will be deferred until a future module.)

You will learn that a Set object cannot contain duplicate elements, but a List object can contain duplicate elements.

You will learn about the difference between ordered collections and sorted collections. You will also learn about ascending order and the natural ordering of objects.

In addition, you will learn how more specialized stipulations are placed on interfaces as you progress downthe interface inheritance hierarchy of the Java Collections Framework.

Generics

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

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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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