java.lang

Annotation Type SafeVarargs


  • @Documented
    @Retention(value=RUNTIME)
    @Target(value={CONSTRUCTOR,METHOD})
    public @interface SafeVarargs
    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 non-reifiable variable arity (vararg) type and suppresses unchecked warnings about parameterized array creation at call sites.

    In addition to the usage restrictions imposed by its @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 @SafeVarargs annotation, and either:

    • the declaration is a fixed arity method or constructor
    • the declaration is a variable arity method that is neither static nor final.

    Compilers are encouraged to issue warnings when this annotation type is applied to a method or constructor declaration where:

    • The variable arity parameter has a reifiable element type, which includes primitive types, Object, and String. (The unchecked warnings this annotation type suppresses already do not occur for a reifiable element type.)
    • 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
       @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!
       }
       
      leads to a ClassCastException at runtime.

      Future versions of the platform may mandate compiler errors for such unsafe operations.

    See The Java™ Language Specification:
    4.7 Reifiable Types, 8.4.1 Formal Parameters

Document created the 11/06/2005, last modified the 04/03/2020
Source of the printed document:https://www.gaudry.be/en/java-api-rf-java/lang/SafeVarargs.html

The infobrol is a personal site whose content is my sole responsibility. The text is available under CreativeCommons license (BY-NC-SA). More info on the terms of use and the author.

References

  1. View the html document Language of the document:fr Manuel PHP : https://docs.oracle.com

These references and links indicate documents consulted during the writing of this page, or which may provide additional information, but the authors of these sources can not be held responsible for the content of this page.
The author This site is solely responsible for the way in which the various concepts, and the freedoms that are taken with the reference works, are presented here. Remember that you must cross multiple source information to reduce the risk of errors.

Contents Haut