Can use bounded wildcard

Reports generic method parameters that can make use of bounded wildcards.

Example:

void process(Consumer<Number> consumer);

should be replaced with:

void process(Consumer<? super Number> consumer);

This method signature is more flexible because it accepts more types: not only Consumer<Number>, but also Consumer<Object>.

Likewise, type parameters in covariant position:

T produce(Producer<T> p);

should be replaced with:

T produce(Producer<? extends T> p);

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

BoundedWildcard

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Java | Code style issues

To quote Joshua Bloch in Effective Java third Edition:

Use the inspection options to toggle the reporting for:

invariant classes. An example of an invariant class is java.util.List<T> because it both accepts values (via the List.add(T) method) and produces values (via the T List.get() method).
On the other hand, contravariant classes only receive values, for example, java.util.function.Consumer<T> with the only method accept(T). Similarly, covariant classes only produce values, for example, java.util.function.Supplier<T> with the only method T get().
People often use bounded wildcards in covariant/contravariant classes but avoid wildcards in invariant classes, for example, void process(List<? extends T> l). Disable this option to ignore such invariant classes and leave them rigidly typed, for example, .
void process(List<T> l)
private methods, which can be considered as not a part of the public API
instance methods

Here you can find the description of settings available for the Can use bounded wildcard inspection, and the reference of their default values.

Last modified: 18 June 2024