Getting compile error on type parameter with multiple bounds

Question

Why am I getting this compiler error on FuzzyWuzzyContainer?

Bound mismatch:The type FuzzyWuzzy is not a valid substitute for the bounded parameter <T extends Fuzzy & Comparable<T>> of the type FuzzyContainer

FuzzyWuzzy does in fact implement both interfaces that are defined in the bounded generic.

public interface Fuzzy
{
    boolean isFuzzy();
}

public class FuzzyWuzzy implements Fuzzy, Comparable<Fuzzy>
{
    public boolean isFuzzy() {return true;}
    public int compare(Fuzzy o) {return 0;)
}

public abstract class FuzzyContainer<T extends Fuzzy & Comparable<T>>
{
   :
}

public class FuzzyWuzzyContainer extends Fuzzycontainer<FuzzyWuzzy> // Error is here
{
}

Answer 1

The problem is FuzzyWuzzy implements Comparable<Fuzzy>. The FuzzyContainer is expecting both Ts in FuzzyContainer<T extends Fuzzy & Comparable<T>> to be the same type. FuzzyWuzzy implements Fuzzy but it doesn't implement Comparable<FuzzyWuzzy>.

Try, FuzzyWuzzy implements Fuzzy, Comparable<FuzzyWuzzy>

Answer 2

Try declaring FuzzyContainer like this:

public abstract class FuzzyContainer<T extends Fuzzy & Comparable<? super T>>

This is necessary since FuzzyWuzzy implements Comparable<Fuzzy> rather than Comparable<FuzzyWuzzy> (you could also make that change, as The Cat pointed out).