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List Basics: Adding, Removing, and Accessing
4:35In this video we'll learn the three basic functions of a list: adding items, removing items, and accessing items!
To get a better feel for how to use lists,
we'll need to use them in code.
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Let's create a new project.
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Hit Next and take it from a template.
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And let's call that project, Lists.
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Then I'll full screen my screen.
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And hide the side panel,
then let's delete the comment.
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And inside,
let's create a new list variable.
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And notice that before we finish typing,
it's telling us something about lists.
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For one, List green I tells
us the list is an interface.
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Also thanks to the angle brackets, we know
that a list can take in a type parameter.
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So instead of just making
this a list of objects,
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let's make it a list of strings and
use Alt+Enter to import list.
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Then let's name our list groceryLine and
set it equal to a new list of strings.
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So = new List<String>() and ;.
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But, of course, since list is
an interface, this won't work.
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Instead, we'll need to use a class
that implements the list interface.
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There's a few choices for this, but
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almost always you'll want
to just use an ArrayList.
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So let's just add Array right before List,
And then use Alt+Enter to import it.
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Also, note that while we can use
an ArrayList on the left side as well,
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we're better off leaving it as a list.
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This way, later on if we ever decide
to use a different implementation of
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the list interface, we can just update
it over here and be done with it.
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Let's also use Alt+Enter to
shorten up the right side.
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Okay, now that we've got our grocery line,
let's add a couple people to it.
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On the next line,
let's type groceryLine.add and
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notice that we've got a few ways
we can add items to a list.
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We can add an item to the end of the list,
add an item at a specified index.
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Add a group of items, or
add a group of items at a specified index.
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Let's stick with the basic add function,
and
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pass in Jerome for
the first person in line.
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Then let's do this two more times,
and add Beth.
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And let's also add Sam.
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Finally, let's print out our list and
see what we've got.
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Let's type sout and tab to bring up the
println statement and pass in groceryLine.
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Then let's run the app, And nice,
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we're able to see exactly what's
in the list just by printing it.
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Okay, now let's say it's been something
like 30 minutes, and Beth has had enough.
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She's got places to be so
she leaves the line.
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Let's add a couple lines and
then remove Beth from our groceryLine
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by calling groceryLine.remove and
passing in Beth.
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Then let's print out
our grocery line again.
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And run the app.
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Perfect.
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We removed Beth from the line.
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You can also remove items by
passing in the index of the item
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you'd like to remove.
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So another way to remove Beth
would be to pass in index 1.
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And if we run the app,
we get the same result.
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Now that we've covered adding and
removing,
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let's talk about how we
access the items in a list.
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Unlike an array, where you put the index
between square brackets, with a list,
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you just call the get function and
pass in the index of the item.
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So if we wanted to create a new
String variable named jerome,
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and set it equal to Jerome,
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we'd set it equal to groceryLine.get and
pass in 0 for the index.
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And if we print out our new
string variable, Called Jerome,
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we should see Jerome.
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Awesome, with that out of the way,
you're ready to get started using lists.
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Just wait till after the next video.
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There's a few more functions,
that you really should know about
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