[jolux]

Java interfaces are not structurally typed, are they?

[garethrowlands]

No but it's the closest available. Two classes C1 and C2 that both implement interfaces I1 and I2 can be said to have a common structure. That is, if they both implement I1 and I2 then they have that structure in common.

[jolux]

Yeah but that’s still fully nominal typing, you can’t implement the interface implicitly, it has to be identified by name.