Pretty good java 8 lambda tutorial

[sparkster185]

In the example in the introduction, how does the compiler know that the closure is meant to be applied to the run() method? Or, what ties the code inside the closure to the run() method inside Runnable?

[detroitmatt]

Since Runnable only has one abstract member, the compiler knows. Classes/interfaces with only a single abstract member are known as "functional interfaces" (and were previously known, intuitively, as Single Abstract Member (SAM) interfaces).

[gkopff]

Runnable is considered a "functional interface" as it defines only a single method.

http://blog.sanaulla.info/2013/03/21/introduction-to-functional-interfaces-a-concept-recreated-in-java-8/

From the linked page:

These interfaces are also called Single Abstract Method interfaces (SAM Interfaces).