/*
* Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package java.lang;
import java.lang.annotation.*;
/**
* A programmer assertion that the body of the annotated method or
* constructor does not perform potentially unsafe operations on its
* varargs parameter. Applying this annotation to a method or
* constructor suppresses unchecked warnings about a
* <i>non-reifiable</i> variable arity (vararg) type and suppresses
* unchecked warnings about parameterized array creation at call
* sites.
*
* <p> In addition to the usage restrictions imposed by its {@link
* Target @Target} meta-annotation, compilers are required to implement
* additional usage restrictions on this annotation type; it is a
* compile-time error if a method or constructor declaration is
* annotated with a {@code @SafeVarargs} annotation, and either:
* <ul>
* <li> the declaration is a fixed arity method or constructor
*
* <li> the declaration is a variable arity method that is neither
* {@code static} nor {@code final}.
*
* </ul>
*
* <p> Compilers are encouraged to issue warnings when this annotation
* type is applied to a method or constructor declaration where:
*
* <ul>
*
* <li> The variable arity parameter has a reifiable element type,
* which includes primitive types, {@code Object}, and {@code String}.
* (The unchecked warnings this annotation type suppresses already do
* not occur for a reifiable element type.)
*
* <li> The body of the method or constructor declaration performs
* potentially unsafe operations, such as an assignment to an element
* of the variable arity parameter's array that generates an unchecked
* warning. Some unsafe operations do not trigger an unchecked
* warning. For example, the aliasing in
*
* <blockquote><pre>
* @SafeVarargs // Not actually safe!
* static void m(List<String>... stringLists) {
* Object[] array = stringLists;
* List<Integer> tmpList = Arrays.asList(42);
* array[0] = tmpList; // Semantically invalid, but compiles without warnings
* String s = stringLists[0].get(0); // Oh no, ClassCastException at runtime!
* }
* </pre></blockquote>
*
* leads to a {@code ClassCastException} at runtime.
*
* <p>Future versions of the platform may mandate compiler errors for
* such unsafe operations.
*
* </ul>
*
* @jls 4.7 Reifiable Types
* @jls 8.4.1 Formal Parameters
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.CONSTRUCTOR, ElementType.METHOD})
public @interface SafeVarargs {}