Getting generic parameter from supertype class

Question

Say I have a parent interface/class like so

interface Parent {}

And a number of implementing interfaces that fix the generic type.

Answer 1

If you need to do anything non-trivial with generic types at runtime, consider Guava's TypeToken. It can answer your question (and many more!) while addressing some of the nuanced concerns raised by commenters:

private interface Parent {}
private interface Intermediate extends Parent {}
private interface Child extends Comparable, Intermediate> {}

public void exploreGuavaTypeTokens() {
    final TypeToken token = TypeToken.of(Child.class).getSupertype(Parent.class);
    final TypeToken resolved = token.resolveType(Parent.class.getTypeParameters()[0]);
    System.out.println(resolved); // "java.lang.Iterable"
    final Class raw = resolved.getRawType();
    System.out.println(raw); // "interface java.lang.Iterable"
}