EventBusBuilder

[greenrobot]

Do all the optional configuration using a builder pattern. Current way with configure* methods are clumsy. This allows more configuration if required.

Existing config:

• logSubscriberExceptions
• logNoSubscriberMessages

Potential new config:

• fail fast (don't send event)
• Give a thread pool for EventBus
• disable sending no-subscriber events
• allow register subscribers without event handlers (Silencing exception on registered object without onEvent method #98)
• allow unregister to succeed if subscriber was not registered before

Q: Should there be a default builder used for the default bus instance? Or should the default bus be setable?

[greenrobot]

378c086