How to restrict generic type of interface to accept only implementor class

Question

My case is different but as an example

public interface Comparable<T> 

would allow me to say:

public class MyType implements Comparable<OtherType>

but this is rarely what you want to achieve.

Is there a way to force me to say:

public class MyType implements Comparable<MyType>

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The closest I got is:

public interface Comparable<T extends Comparable<T>>

This only works partially, as it won't allow OtherType if it's not comparable itself, but would allow:

public class MyType implements Comparable<Integer>

as it meets the conditions.

Answer 1

This is not possible in Java.

Consider if it were possible to require that the type argument of Comparable be the same as the implementing class. Then if you had a class Foo implements Comparable<Foo> , and then also a class Bar extends Foo , Bar would also automatically implement Comparable<Foo> by the way that inheritance in Java works. But that would violate the constraint that the implementing class is the same as the type argument, as Bar does not implement Comparable<Bar> (and you can't even explicitly have Bar implement Comparable<Bar> , as a class cannot implement a generic type with two different type arguments).