Java SE 8 will add a number of "functional interface" types, such as Predicate or Block, to act as conversion targets for lambda expressions and method references.

The initial set is:
Predicate<T> : T -> boolean
Block<T> : T -> void
Mapper<T, U>: T -> U
UnaryOperator<T>: T -> T
BinaryOperator<T>: (T,T) -> T
BiBlock<T,U>: (T,U) -> void
BiMapper<T,U,V>: (T,U) -> V
BiPredicate<T,U>: (T,U> -> boolean
Factory<T>: () -> T

and would live in java.util.functions.