parrt/antlr4 — pull request #34 by sharwell (2012-03-07 13:54:14+00:00)
Title: Default error listener

* `Recognizer._listeners` initialized to have a single `ConsoleErrorListener`
* Use `CopyOnWriteArrayList` so listeners can be added/removed in callbacks
* Remove special handling for `_listeners` null or empty (never null, `ConsoleErrorListener` will be present if feature is desired)