org.checkerframework.framework.qual

Annotation Type Covariant

@Documented
 @Retention(value=RUNTIME)
 @Target(value=TYPE)
public @interface Covariant

A marker annotation, written on a class declaration, that signifies that one or more of the class's type parameters can be treated covariantly. For example, if MyClass has a single type parameter that is treated covariantly, and if B is a subtype of A, then SomeClass<B> is a subtype of SomeClass<A>.

Ordinarily, Java treats type parameters invariantly: SomeClass<B> is unrelated to (neither a subtype nor a supertype of) SomeClass<A>.

It is only safe to mark a type parameter as covariant if the type parameter is used in a read-only way: values of that type are read from but never modified. This property is not checked; the @Covariant is simply trusted.

Here is an example use:

 @Covariant(0)
 public interface Iterator<E extends @Nullable Object> { ... }
 

See the Checker Framework Manual:

Covariant type parameters

Required Element Summary

Required Elements

Modifier and Type	Required Element and Description
int[]	value The zero-based indices of the type parameters that should be treated covariantly.

Element Detail

value

public abstract int[] value

The zero-based indices of the type parameters that should be treated covariantly.