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/*
* [The "BSD license"]
* Copyright (c) 2012 Terence Parr
* Copyright (c) 2012 Sam Harwell
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.antlr.v4.runtime.misc;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* This annotation marks a field, parameter, local variable, or method (return
* value) as potentially having the value {@code null}. The specific semantics
* implied by this annotation depend on the kind of element the annotation is
* applied to.
*
* <ul>
* <li><strong>Field or Local Variable:</strong> Code reading the field or local
* variable may not assume that the value is never {@code null}.</li>
* <li><strong>Parameter:</strong> Code calling the method might pass
* {@code null} for this parameter. The documentation for the method should
* describe the behavior of the method in the event this parameter is
* {@code null}.
* </li>
* <li><strong>Method (Return Value):</strong> Code calling the method may not
* assume that the result of the method is never {@code null}. The documentation
* for the method should describe the meaning of a {@code null} reference being
* returned. Overriding methods may optionally use the {@link NotNull}
* annotation instead of this annotation for the method, indicating that the
* overriding method (and any method which overrides it) will never return a
* {@code null} reference.</li>
* </ul>
*
* <p>
* The {@link NullUsageProcessor} annotation processor validates certain usage
* scenarios for this annotation, with compile-time errors or warnings reported
* for misuse. For detailed information about the supported analysis, see the
* documentation for {@link NullUsageProcessor}.</p>
*/
@Documented
@Retention(RetentionPolicy.CLASS)
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.LOCAL_VARIABLE})
public @interface Nullable {
}
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