Groovy def l = [1, 2, 3] as BlockingQueue

Question

If I write something like def l = [1, 2, 3] as Socket which is obviously nonsense, I get this:

org.codehaus.groovy.runtime.typehandling.GroovyCastE         


        

Answer 1

why am I able to cast the list to BlockingQueue without error despite the fact that it fails (l doesn't end up being an BlockingQueue instance)?

Why are you so sure that l is not a BlockingQueue instance? The following (which you can run in the Groovy console) indicates that it is a BlockingQueue instance:

import java.util.concurrent.BlockingQueue

// this assignment would be impossible if l is not a BlockingQueue
BlockingQueue l = [1, 2, 3] as BlockingQueue

// this assertion would throw an exception if l is not a BlockingQueue
assert l instanceof BlockingQueue

FYI, you can remove a lot of uncertainty about types by defining the types of your variables, rather than using def.