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This module presents and explains several simple programs that provide a first look into Java Generics.

Revised: Wed May 11 17:07:35 CDT 2016

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Table of Contents

Preface

This module is one in a collection of modules on Java Generics designed for teaching ITSE2317 - Java Programming (Intermediate) at Austin Community College in Austin, TX.

Many new features in Java version 1.5

When Java version 1.5 was released, it contained many new language features, including:

  • Generics
  • Enhanced for Loop
  • Autoboxing/Unboxing
  • Typesafe Enums
  • Varargs
  • Static Import
  • Metadata

In addition to the new language features, Java version 1.5 also contained other new features such as new Look and Feel capabilities for Swing GUIs.

First in a series

This is the first module in a series of modules designed to teach you about Generics in Java version 1.5. Thismodule will teach you some of the rudimentary aspects of the generics capability . This module will also teach you how to use the enhanced for loop with collections.

Future modules will teach you how to use other aspects of generics

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 Figuresand the Listings while you are reading about them.

Figures

Listings

General background information

A new compiler warning

Have you recently tried to recompile a legacy program that has compiled and executed properly for many years only to get a compiler message similar to thatshown in Figure 1 ?

Figure 1 - Typical v1.5 compiler warning.
Note: Generics01.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details.

If you followed up and recompiled as directed, you probably got a message from the compiler that looked something like the one shown in Figure 2 .

Figure 2 - Warning with -Xlint:unchecked.
Generics01.java:34: warning: [unchecked] unchecked call to add(E) as a member ofthe raw type ArrayList var1.add(new Date());^ where E is a type-variable:E extends Object declared in class ArrayList 1 warning

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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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