<!DOCTYPE qhelp PUBLIC

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<qhelp>

<overview>

<p>Anonymous classes are a common way of creating implementations of an interface

or abstract class whose functionality is

really only needed once. Duplicating the definition of an anonymous class in several

places is usually a sign that refactoring is necessary.</p>

<p>Code duplication in general is highly undesirable for a range of reasons. The artificially

inflated amount of code is more difficult to understand, and sequences of similar but subtly different lines

can mask the real purpose or intention behind them. Also, there is always a risk that only one

of several copies of the code is updated to address a defect or add a feature.</p>

</overview>

<recommendation>

<p>Introduce a concrete class

that contains the definition just once, and replace the anonymous classes with instances

of this concrete class.</p>

</recommendation>

<example>

<p>In the following example, the definition of the class <code>addActionListener</code> is duplicated for

each button that needs to use it. A better solution is shown that defines just one class,

<code>MultiplexingListener</code>, which is used by each button.</p>

<sample src="DuplicateAnonymous.java" />

</example>

<references>

<li>E. Juergens, F. Deissenboeck, B. Hummel, S. Wagner.

<em>Do code clones matter?</em> Proceedings of the 31st International Conference on

Software Engineering,

485-495, 2009.</li>

</references>

</qhelp>