如何将复杂的泛型方法应用于通配符泛型类型的类？

Question

There are something like:

<T> Identifier<Set<T>> myMethod(Iterable<? extends Element<Identifier<T>>> input) {…}

class MyClass implements Element<Identifier<?>> {…}

Iterable<MyClass> a = …;

How could I pass a to myMethod to get Identifier<Set<?>> ?

Answer 1

Simply blabla.myMethod((Iterable) a) ;

More specifically:

Identifier<Set<?>> setIdentifier = blabla.myMethod((Iterable) a);

Answer 2

If you have control over myMethod , make its signature more flexible:

<T> Identifier<Set<T>> myMethod(Iterable<? extends Element<Identifier<? extends T>>> input)

And while that's enough to solve your issue, this would be the most flexible:

<T> Identifier<Set<T>> myMethod(Iterable<? extends Element<? extends Identifier<? extends T>>> input)

See also:

• What is PECS (Producer Extends Consumer Super)?
• Multiple wildcards on a generic methods makes Java compiler (and me!) very confused