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<b>Trail:</b> Learning the Java Language

<br /><b>Lesson:</b> Generics (Updated)

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<div class="linkLESSON"><a href="index.html">Generics (Updated)</a></div>

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<div id="PageTitle"><h1>Why Use Generics?</h1></div>

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In a nutshell, generics enable <em>types</em> (classes and interfaces) to be parameters when defining classes, interfaces and methods. Much like the more familiar <em>formal parameters</em> used in method declarations, type parameters provide a way for you to re-use the same code with different inputs. The difference is that the inputs to formal parameters are values, while the inputs to type parameters are types.</p>

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Code that uses generics has many benefits over non-generic code:</p>

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<li>Stronger type checks at compile time.<br />

A Java compiler applies strong type checking to generic code and issues errors if the code violates type safety. Fixing compile-time errors is easier than fixing runtime errors, which can be difficult to find.<br /><br /></li>

<li>Elimination of casts.<br />

The following code snippet without generics requires casting:

<div class="codeblock"><pre>

List list = new ArrayList();

list.add("hello");

String s = <strong>(String)</strong> list.get(0);

</pre></div>

When re-written to use generics, the code does not require casting:

<div class="codeblock"><pre>

List&lt;String&gt; list = new ArrayList&lt;String&gt;();

list.add("hello");

String s = list.get(0); // no cast

</pre></div>

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<li>Enabling programmers to implement generic algorithms.<br />

By using generics, programmers can implement generic algorithms that work on collections of different types, can be customized, and are type safe and easier to read.</li>

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