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<title>EXPERIMENTAL - @ExtensionMethod</title>
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<div class="header"><a href="../../index.html">Project Lombok</a></div>
<h1>@Value</h1>
<div class="byline">Immutable classes made very easy.</div>
<div class="since">
<h3>Since</h3>
<p>
@Value was introduced as experimental feature in lombok v0.11.4.
</p>
</div>
<div class="experimental">
<h3>Experimental</h3>
<p>
Experimental because:
<ul>
<li>Various choices still have to be vetted as being the correct 'least surprise' choice: Should the class be made final by default, etc.</li>
<li>Dependent on @Wither which is experimental.</li>
</ul>
Current status: <em>positive</em> - Currently we feel this feature may move out of experimental status with no or minor changes soon.
</div>
<div class="overview">
<h3>Overview</h3>
<p>
<code>@Value</code> is the immutable variant of <a href="../Data.html"><code>@Data</code></a>; all fields are made <code>private</code> and <code>final</code> by default, and instead of setters, each field gets a so-called 'wither',
which is a method that produces a clone with each field having the same value, except for the field you want a new value for. The class itself is also made <code>final</code> by default, because immutability is not something that can
be forced onto a subclass. Like <code>@Data</code>, useful <code>toString()</code>, <code>equals()</code> and <code>hashCode()</code> methods are also generated, each field gets a getter method, and a constructor that covers every
argument (except <code>final</code> fields that are initialized in the field declaration) is also generated.
</p><p>
In practice, <code>@Value</code> is shorthand for: <code>final @ToString @EqualsAndHashCode @AllArgsConstructor @FieldDefaults(makeFinal = true, level = AccessLevel.PRIVATE) @Getter @Wither</code>.
</p><p>
It is possible to override the final-by-default and private-by-default behaviour using either an explicit access level on a field, or by using the <code>@NonFinal</code> or <code>@PackagePrivate</code> annotations.<br />
It is possible to override any default behaviour for any of the 'parts' that make up <code>@Value</code> by explicitly using that annotation.
</p>
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<h3>With Lombok</h3>
<div class="snippet">@HTML_PRE@</div>
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<h3>Vanilla Java</h3>
<div class="snippet">@HTML_POST@</div>
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<div class="overview">
<h3>Small print</h3><div class="smallprint">
<p>
Look for the documentation on the 'parts' of <code>@Value</code>: <a href="../ToString.html"><code>@ToString</code></a>, <a href="../EqualsAndHashCode.html"><code>@EqualsAndHashCode</code></a>,
<a href="../Constructor.html"><code>@AllArgsConstructor</code></a>, <a href="FieldDefaults.html"><code>@FieldDefaults</code></a>, <a href="../GetterSetter.html"><code>@Getter</code></a>,
<a href="Wither.html"><code>@Wither</code></a>.
</p><p>
For classes with generics, it's useful to have a static method which serves as a constructor, because inference of generic parameters via static methods works in java6 and avoids having to use the diamond operator.
While you can force this by applying an explicit <code>@AllArgsConstructor</code> annotation, there's also the <code>@Value(staticConstructor="of")</code> feature, which will make the generated all-arguments constructor
private, and generates a public static method named <code>of</code> which is a wrapper around this private constructor.
</p>
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