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/*
* Copyright © 2009 Reinier Zwitserloot and Roel Spilker.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package lombok;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Generates implementations for the {@code equals} and {@code hashCode} methods inherited by all objects.
* <p>
* If either method already exists, then {@code @EqualsAndHashCode} will not generate that particular method.
* If they all exist, {@code @EqualsAndHashCode} generates no methods, and emits a warning instead to highlight
* that its doing nothing at all. The parameter list and return type are not relevant when deciding to skip generation of
* a method; any method named {@code hashCode} will make {@code @EqualsAndHashCode} not generate that method,
* for example.
* <p>
* By default, all fields that are non-static and non-transient are used in the equality check and hashCode generation.
* You can exclude more fields by specifying them in the {@code exclude} parameter. You can also explicitly specify
* the fields that are to be used by specifying them in the {@code of} parameter.
* <p>
* Normally, auto-generating {@code hashCode} and {@code equals} implementations in a subclass is a bad idea, as
* the superclass also defines fields, for which equality checks/hashcodes won't be auto-generated. Therefore, a warning
* is emitted when you try. Instead, you can set the {@code callSuper} parameter to <em>true</em> which will call
* {@code super.equals} and {@code super.hashCode}. Doing this with {@code java.lang.Object} as superclass is
* pointless, so, conversely, setting this flag when <em>NOT</em> extending something (other than Object) will also generate
* a warning. Be aware that not all implementations of {@code equals} correctly handle being called from a subclass!
* Fortunately, lombok-generated {@code equals} implementations do correctly handle it.
* <p>
* Array fields are handled by way of {@link java.util.Arrays#deepEquals(Object[], Object[])} where necessary, as well
* as {@code deepHashCode}. The downside is that arrays with circular references (arrays that contain themselves,
* possibly indirectly) results in calls to {@code hashCode} and {@code equals} throwing a
* {@link java.lang.StackOverflowError}. However, the implementations for java's own {@link java.util.ArrayList} suffer
* from the same flaw.
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.SOURCE)
public @interface EqualsAndHashCode {
/**
* Any fields listed here will not be taken into account in the generated
* {@code equals} and {@code hashCode} implementations.
* Mutually exclusive with {@link #of()}.
*/
String[] exclude() default {};
/**
* If present, explicitly lists the fields that are to be used for identity.
* Normally, all non-static, non-transient fields are used for identity.
* <p>
* Mutually exclusive with {@link #exclude()}.
*/
String[] of() default {};
/**
* Call on the superclass's implementations of {@code equals} and {@code hashCode} before calculating
* for the fields in this class.
* <strong>default: false</strong>
*/
boolean callSuper() default false;
}
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