Correct. It's a closure when anything is captured, whether that's a local variable or the object on which a method is called. And here's an interesting thing - that also includes the enclosing object or any of its fields that you use.
Consider the following:
When you try to run this, you'll get an exception:
This shows that the enclosing
Test instance is captured by the lambda, as it is also being serialised (which causes the exception). Remove the line that accesses "this" and it will work.