java.lang.SafeVarargs Maven / Gradle / Ivy
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*
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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
* 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 {@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:
*
* - the declaration is a fixed arity method or constructor
*
*
- the declaration is a variable arity method that is neither
* {@code static} nor {@code 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, {@code Object}, and {@code 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 {@code ClassCastException} at runtime.
*
* Future versions of the platform may mandate compiler errors for
* such unsafe operations.
*
*
*
* @jls 4.7 Reifiable Types
* @jls 8.4.1 Formal Parameters
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.CONSTRUCTOR, ElementType.METHOD})
public @interface SafeVarargs {}