> "This is okay for exploration, but which data structure from java.util.concurrent am I going to have swap in here when it's all done. That just doesn't work

> "This is okay for exploration, but which data structure from java.util.concurrent am I going to have swap in here when it's all done. That just doesn't work for most concurrent code. Often you have dependencies between data structures or other operations intervening. Most of the time it isn't a single structure, but a group of semantic operations across the program.