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<title>@Data</title>
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<div class="header"><a href="../index.html">Project Lombok</a></div>
<h1>@Data</h1>
<div class="byline">'struct' for java: Automatically generate <code>toString</code>, <code>hashCode</code>, <code>equals</code>, a constructor, and getters and setters
from just the fields in your class.</div>
<div class="overview">
<h3>Overview</h3>
<p>
Any class definition may be annotated with <code>@Data</code> to let lombok generate all the boilerplate that is associated with simple POJOs
(Plain Old Java Objects) and beans: getters for all fields, setters for all non-final fields, a useful <code>toString</code>, and implementations
of <code>hashCode</code> and <code>equals</code> which consider any two objects of this type with the same values for each field as equal. A
constructor is also generated containing 1 parameter for each final field, in the order the fields are defined. This constructor simply assigns
each parameter to the appropriate field.
</p>
<p>
To override the access level of any getter/setter for any field, annotate the field with a <code>@Setter</code> or <code>@Getter</code> annotation
with the appropriate <code>AccessLevel</code> value. See the example below. For more information on how the getters/setters are generated,
see the documentation for <a href="GetterSetter.html"><code>@Getter</code> and <code>@Setter</code></a>.
</p><p>
All fields marked as <code>transient</code> will not be considered for <code>hashCode</code> and <code>equals</code>. All static fields will be
skipped entirely (not considered for any of the generated methods, and no setter/getter will be made for them).
The generated getter/setter method will be <code>public</code> unless you explicitly specify an <code>AccessLevel</code>, as shown in the example below.
Legal access levels are <code>PUBLIC</code>, <code>PROTECTED</code>, <code>PACKAGE</code>, and <code>PRIVATE</code>.
</p><p>
If any method that would normally be generated exists <em>in name</em> that method will not be generated, and no warning or error is emitted. For example,
if you already have a method with signature <code>void hashCode(int a, int b, int c)</code>, no <code>int hashCode()</code> method will be generated,
even though technically <code>int hashCode()</code> is an entirely different method. The same rule applies to the constructor, <code>toString</code>,
<code>hashCode</code>, and all getters and setters.
</p><p>
<code>@Data</code> can handle generics parameters for fields just fine. In order to reduce the boilerplate when constructing objects for classes with
generics, you can use the <code>staticConstructor</code> parameter to generate a private constructor, as well as a static method that returns a new
instance. This way, javac will infer the variable name. Thus, by declaring like so: <code>@Data(staticConstructor="of") class Foo<T> { private T x;}</code>
you can create new instances of <code>Foo</code> by writing: <code>Foo.of(5);</code> instead of having to write: <code>new Foo<Integer>(5);</code>.
</p>
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<div class="snippets">
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<h3>With Lombok</h3>
<div class="snippet">@HTML_PRE@</div>
</div>
<div class="sep"></div>
<div class="post">
<h3>Vanilla Java</h3>
<div class="snippet">@HTML_POST@</div>
</div>
</div>
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<div class="overview">
<h3>Small print</h3><div class="smallprint">
<p>
Arrays are 'deep' compared/printed/hashCoded, which means that arrays that contain themselves will result in <code>StackOverflowError</code>s. However,
this behaviour is no different from e.g. <code>ArrayList</code>.
</p><p>
You may safely presume that the hashCode implementation used will not change between versions of lombok, however this guarantee is not set in stone;
if there's a significant performance improvement to be gained from using an alternate hash algorithm, that will be substituted in a future version.
</p><p>
For a general idea of how lombok generated the <code>equals</code>, <code>hashCode</code>, and <code>toString</code> methods, check the example after.
</p><p>
For the purposes of equality, 2 <code>NaN</code> (not a number) values for floats and doubles are considered equal, eventhough 'NaN == NaN' would
return false. This is analogous to <code>java.lang.Double</code>'s equals method, and is in fact required to ensure that comparing an object
to an exact copy of itself returns <code>true</code> for equality.
</p>
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<a href="../credits.html" class="creditsLink">credits</a> | <span class="copyright">Copyright © 2009 Reinier Zwitserloot and Roel Spilker, licensed under the <a href="http://www.opensource.org/licenses/mit-license.php">MIT licence</a>.</span>
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