Lambda expressions - Java 8 in Action: Lambdas, Streams, and Functional-Style Programming - page 67

Figure 3.4. Deconstructing the type-checking process of a lambda
expression
List<Apple> heavierThan150g =
filter(inventory, (Apple a) -> a.getWeight() > 150 );
The type-checking process is deconstructed as follows:
 First, you look up the declaration of the filter method.
 Second, it expects as the second formal parameter an object of type Predicate-<Apple> (the target
type).
 Third, Predicate<Apple> is a functional interface defining a single abstract method called test .
 Fourth, the method test describes a function descriptor that accepts an Apple and returns a
boolean .