Advanced Collections and Collectors - Java 8 Lambdas - page 64

( name , nationality ) -> new new Artist ( name , nationality )

We can also write this using method references:

Artist: : new new

This code is not only shorter but also a lot easier to read. Artist::new immediately tells you
that you're creating a new Artist without your having to scan the whole line of code.
Another thing to notice here is that method references automatically support multiple para-
meters, as long as you have the right functional interface.

It's also possible to create arrays using this method. Here is how you would create a String
array:

String []:: new new

We'll be using method references from this point onward where appropriate, so you'll be
seeing a lot more examples very soon. When we were first exploring the Java 8 changes, a
friend of mine said that method references “feel like cheating.” What he meant was that, hav-
ing looked at how we can use lambda expressions to pass code around as if it were data, it
felt like cheating to be able to reference a method directly.

It's OK—it's not cheating! You have to bear in mind that every time you write a lambda ex-
pression that looks like x -> foo(x) , it's really doing the same thing as just the method foo
on its own. All method references do is provide a simpler syntax that takes advantage of this
fact.

Element Ordering

One topic I haven't discussed so far that pertains to collections is how elements are ordered
in streams. You might be familiar with the concept that some types of Collection , such as
List , have a defined order, and collections like HashSet don't. The situation with ordering
becomes a little more complex with Stream operations.

A Stream intuitively presents an order because each element is operated upon, or en-
countered, in turn. We call this the encounter order . How the encounter order is defined de-
pends on both the source of the data and the operations performed on the Stream .