<!DOCTYPE qhelp PUBLIC

"-//Semmle//qhelp//EN"

"qhelp.dtd">

<qhelp>

<overview>

<p>

The use of generics in Java improves compile-time type safety and

code readability.

Users of a class or interface that has been designed using generic types

should therefore make use of parameterized instances

in variable declarations, method return types, and constructor calls.

</p>

</overview>

<recommendation>

<p>

Provide type parameters to generic classes and interfaces where possible.

</p>

<p>

Note that converting legacy code to use generics may

have to be done carefully in order to preserve the existing

functionality of an API; for detailed guidance, see the references.

</p>

</recommendation>

<example>

<p>The following example is poorly written because it uses raw types. This makes it

more error prone because the compiler is less able to perform type checks.</p>

<sample src="Generics_Common.java" />

<p>A parameterized version can be easily made and is much safer.</p>

<sample src="Generics_CommonGood.java" />

</example>

<references>

<li>

J. Bloch, <em>Effective Java (second edition)</em>,

Item 23.

Addison-Wesley, 2008.

</li>

<li>

Help - Eclipse Platform:

<a href="http://help.eclipse.org/indigo/index.jsp?topic=%2Forg.eclipse.jdt.doc.user%2Freference%2Fpreferences%2Fjava%2Fcompiler%2Fref-preferences-errors-warnings.htm">Java Compiler Errors/Warnings Preferences</a>.

</li>

<li>

The Java Tutorials:

<a href="http://docs.oracle.com/javase/tutorial/java/generics/">Generics</a>,

<a href="http://docs.oracle.com/javase/tutorial/extra/generics/convert.html">Converting Legacy Code to Use Generics</a>.

</li>

</references>

</qhelp>