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In this video we'll talk about where Lists came from and what types of problems they solve!
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[MUSIC]
0:00
In the past few courses we learned about
inheritance, interfaces, and generics.
0:09
And when Java launched in 1995,
that was the end of the story.
0:14
However, it didn't take long
before developers wanted more.
0:19
One place Java seemed to
be lacking was with arrays.
0:23
At this point,
if we have a collection of objects,
0:26
the only way we can store
them is with an array.
0:29
And arrays work great for
things that have a fixed size,
0:33
like the number of months in a year or
number of squares on a chess board.
0:36
But arrays don't work so well when
the size of the collection changes.
0:40
For example, let's look at
the checkout line at the grocery.
0:44
Right now,
there's only a couple of people in line.
0:47
But if we jump forward to the holidays,
there's a ton of people here.
0:50
So if we wanted to use an array to store
all the people in line we'd need to make
0:54
the array big enough to
handle the holidays.
0:59
Which means most of the year,
our array would just be taking up space.
1:02
It'd be as if the grocery left
their queues up all year.
1:06
To fix this problem, in 1998 we got
the Java Collections framework.
1:11
A set of classes and
interfaces which give us a lot
1:16
more flexibility in how we
store collections of objects.
1:19
Now the Java Collections framework is made
up of a lot of classes and interfaces.
1:23
But for the most part,
1:28
there's only two types of collection that
we'll use frequently, lists and maps.
1:29
We'll save maps for a later of course but
right now, let's focus on lists.
1:36
In Java, a list is pretty much
just a more flexible array.
1:41
Like an array, the items are indexed and
we can access them by their index.
1:46
But unlike an array, with a list we can
add or remove items anywhere we like.
1:50
We also get a few helpful methods, like
contains() which returns a Boolean telling
1:56
us if a list contains a certain item.
2:01
And indexOf() which searches the list for
an item and
2:03
returns the index of that item, if it's
found, or negative one if it's not.
2:07
In addition to being a more
flexible version of arrays,
2:13
lists also give us a bunch of methods
to help deal with groups of objects.
2:16
In fact, in most cases you'll probably
end up using a list instead of an array.
2:20
Let's see how to use
a list in the next video.
2:26
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