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Sneak Peak: Method References
3:35Java 8 also introduces method references and allows them to be used anywhere a Functional Interface AKA Single Abstract Method is expected.
Up until now we've been
using anonymous functions.
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But it's also possible to use
a thing called method references.
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And we can use those in place
of where lambdas are expected.
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The compiler does some
crazy smart stuff for
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you, which we'll explore in
depth in a different course.
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But I wanted to just give you
this version of the code,
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as it's probably the correct way
to solve this using functions.
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It may also be a little hard
to read if it's new to you.
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So let's dupe this,
using lambdas in short form,
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and let's replace this with
using method references.
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The comparator actually added a new
static method called comparing,
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which expects a function.
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So let's go ahead, let's do this.
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So, Comparator.comparing the static
method and it expects a function.
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We could put a lambda here right?
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So we could do this we could say b and
b.getTitle.
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So what that does is it says for each
thing in here compare using the title.
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So, that's a lot cleaner already
using that lambda method.
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But since that style is so common,
you can actually do something like this.
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So, instead of writing
out the lambda there,
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you can actually use a method reference.
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So, what we're gonna say is the class book
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has a method called getTitle on it,
and it should use that.
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Use the getTitle method on each instance
to get the value that will be used for
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the comparing command.
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This takes a little bit to get use to,
but it's super powerful.
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Now it also works with parameters.
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Check this one out.
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So if we say books for each and
we want to print out each one of these,
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we're gonna say system.out.
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And the method that we want to do,
cuz it takes a parameter, is println.
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That returns a reference
to the println method, and
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for each applies the entry as
the parameter to the function.
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Pretty cool, right?
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But it’s definitely gonna take
some time to get used to.
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But don’t let that boggle
your mind too much.
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We’ll go over that fully in
a functional programming course.
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But I just wanted you to see that
double colon style of method reference.
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Okay, so let’s take a quick look
at the evolution of our code.
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So, here is the SAM method, right?
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It’s very long.
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Okay, so let's expand this.
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And again, so
this creates a new anonymous class.
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It's typed.
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We use the name.
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We had to put the override with the method
name, and we defined the method.
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And we put in there return type,
pretty noisy.
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And then it got cleaner.
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We still had the types.
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And then it got a lot cleaner, right.
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So we removed all the return lines,
and now it's onto three lines.
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And if we look down here we're hardly
writing any code at all when we get down
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to the method references.
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See how much cleaner things can become?
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So, there you go, I hope you're happy.
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Oh no, no wait, I hope you are merry
that you had a little intro to lambdas.
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You see what I did there?
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Mary had a little lambda?
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Oh God, you should edit that joke out,
it's so bad.
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>> So there we go.
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I'm glad you got a chance to meet and
get cozy with lambda expressions.
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You'll definitely encounter them as
they're becoming increasingly popular in
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new java code and frameworks.
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Now if you want to delve deeper
into functional programing,
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please be sure to check out
the teacher's notes for more resources.
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We are always looking for
feedback on this format, and
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how we can make it even better.
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Please let us know what you thought,
and also,
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make sure your vote is
heard on upcoming content.
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Thanks for hanging out and
we'll see you very soon.
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