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<#import "_features.html" as f>
<@f.scaffold title="@With" logline="Immutable 'setters' - methods that create a clone but with one changed field.">
<@f.history>
<p>
<code>@Wither</code> was introduced as experimental feature in lombok v0.11.4.
</p><p>
<code>@Wither</code> was renamed to <code>@With</code>, and moved out of experimental and into the core package, in lombok v1.18.10.
</@f.history>
<@f.overview>
<p>
The next best alternative to a setter for an immutable property is to construct a clone of the object, but with a new value for this one field. A method to generate this clone is precisely what <code>@With</code> generates: a <code>withFieldName(newValue)</code> method which produces a clone except for the new value for the associated field.
</p><p>
For example, if you create <code>public class Point { private final int x, y; }</code>, setters make no sense because the fields are final. <code>@With</code> can generate a <code>withX(int newXValue)</code> method for you which will return a new point with the supplied value for <code>x</code> and the same value for <code>y</code>.
</p><p>
Like <a href="/features/GetterSetter"><code>@Setter</code></a>, you can specify an access level in case you want the generated with method to be something other than <code>public</code>:<br /> <code>@With(level = AccessLevel.PROTECTED)</code>. Also like <a href="/features/GetterSetter"><code>@Setter</code></a>, you can also put a <code>@With</code> annotation on a type, which means a <code>with</code> method is generated for each field (even non-final fields).
</p><p>
To put annotations on the generated method, you can use <code>onMethod=@__({@AnnotationsHere})</code>. Be careful though! This is an experimental feature. For more details see the documentation on the <a href="/features/experimental/onX">onX</a> feature.
</p><p>
javadoc on the field will be copied to generated with methods. Normally, all text is copied, and <code>@param</code> is <em>moved</em> to the with method, whilst <code>@return</code> lines are stripped from the with method's javadoc. Moved means: Deleted from the field's javadoc. It is also possible to define unique text for the with method's javadoc. To do that, you create a 'section' named <code>WITH</code>. A section is a line in your javadoc containing 2 or more dashes, then the text 'WITH', followed by 2 or more dashes, and nothing else on the line. If you use sections, <code>@return</code> and <code>@param</code> stripping / copying for that section is no longer done (move the <code>@param</code> line into the section).
</p><p>
If you have a hierarchical immutable data structure, the <a href="/features/experimental/WithBy"><code>@WithBy</code></a> feature might be more suitable than <code>@With</code>
</@f.overview>
<@f.snippets name="With" />
<@f.confKeys>
<dt>
<code>lombok.with.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
</dt><dd>
Lombok will flag any usage of <code>@With</code> as a warning or error if configured.
</dd>
</@f.confKeys>
<@f.smallPrint>
<p>
With methods cannot be generated for static fields because that makes no sense.
</p><p>
With methods can be generated for abstract classes, but this generates an abstract method with the appropriate signature.
</p><p>
When applying <code>@With</code> to a type, static fields and fields whose name start with a $ are skipped.
</p><p>
For generating the method names, the first character of the field, if it is a lowercase character, is title-cased, otherwise, it is left unmodified. Then, <code>with</code> is prefixed.
</p><p>
No method is generated if any method already exists with the same name (case insensitive) and same parameter count. For example, <code>withX(int x)</code> will not be generated if there's already a method <code>withX(String... x)</code> even though it is technically possible to make the method. This caveat exists to prevent confusion. If the generation of a method is skipped for this reason, a warning is emitted instead. Varargs count as 0 to N parameters.
</p><p>
For <code>boolean</code> fields that start with <code>is</code> immediately followed by a title-case letter, nothing is prefixed to generate the wither name.
</p><p>
Various well known annotations about nullity cause null checks to be inserted and will be copied to the parameter. See <a href="/features/GetterSetter">Getter/Setter</a> documentation's small print for more information.
</p>
</@f.smallPrint>
</@f.scaffold>
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