[FLINK-9392] Add @FunctionalInterface annotations to all core functional interfaces

• Type: Improvement
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 1.6.0
• Assignee: Stephan Ewen
• Reporter: Stephan Ewen
• Created: 17/May/18 15:11
• Updated: 28/Feb/19 13:20
• Resolved: 18/May/18 08:12

Description

The @FunctionalInterface annotation should be added to all SAM interfaces in order to prevent accidentally breaking them (as non SAMs).

We had a case of that before for the SinkFunction which was compatible through default methods, but incompatible for users that previously instantiated that interface through a lambda.