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[MUSIC]

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In the past few courses we learned about
inheritance, interfaces, and generics.

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And when Java launched in 1995,
that was the end of the story.

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However, it didn't take long
before developers wanted more.

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One place Java seemed to
be lacking was with arrays.

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At this point,
if we have a collection of objects,

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the only way we can store
them is with an array.

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And arrays work great for
things that have a fixed size,

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like the number of months in a year or
number of squares on a chess board.

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But arrays don't work so well when
the size of the collection changes.

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For example, let's look at
the checkout line at the grocery.

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Right now,
there's only a couple of people in line.

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But if we jump forward to the holidays,
there's a ton of people here.

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So if we wanted to use an array to store
all the people in line we'd need to make

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the array big enough to
handle the holidays.

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Which means most of the year,
our array would just be taking up space.

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It'd be as if the grocery left
their queues up all year.

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To fix this problem, in 1998 we got
the Java Collections framework.

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A set of classes and
interfaces which give us a lot

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more flexibility in how we
store collections of objects.

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Now the Java Collections framework is made
up of a lot of classes and interfaces.

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But for the most part,

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there's only two types of collection that
we'll use frequently, lists and maps.

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We'll save maps for a later of course but
right now, let's focus on lists.

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In Java, a list is pretty much
just a more flexible array.

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Like an array, the items are indexed and
we can access them by their index.

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But unlike an array, with a list we can
add or remove items anywhere we like.

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We also get a few helpful methods, like
contains() which returns a Boolean telling

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us if a list contains a certain item.

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And indexOf() which searches the list for
an item and

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returns the index of that item, if it's
found, or negative one if it's not.

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In addition to being a more
flexible version of arrays,

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lists also give us a bunch of methods
to help deal with groups of objects.

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In fact, in most cases you'll probably
end up using a list instead of an array.

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Let's see how to use
a list in the next video.