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In this video, we look to the Internet for assistance in figuring out how to retrieve an integer from a String.
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So we left our program in
a bit of a broken state.
0:00
What we wanna do is prompt our
user to ask how old they are.
0:03
We know how to do that,
as we've done that already, right?
0:06
But there's a slight problem.
0:08
The method that we've been using,
readLine, well, that returns a String.
0:10
But as we know now,
0:14
when dealing with numbers we want
to use the Integer data type.
0:15
So somehow we need to get
an int from a String.
0:18
I know, how about we ask the Internet and
see what we get back?
0:22
Okay, so I'm gonna go ahead and do a
search for exactly what we're looking for,
0:27
which is Java get an int from a string.
0:31
And we'll take a look at what we got here.
0:38
This very first one is from
a website called Stack Overflow,
0:40
which is a great resource for a developer.
0:43
Lets see if it's, indeed,
what we're looking for.
0:45
It says here, how does one convert
a String to an Int in Java?
0:46
That is exactly what we need.
0:50
See, I have a string which
contains only numbers, and
0:52
I wanna return a number which represents
it, which is what we want to do,
0:55
cuz we want to use the Int
to be compared in there.
0:58
So let's go scroll down to
what the answers are so
1:00
that you see there are seventeen answers,
and this one has a thousand votes.
1:02
You can upvote if it worked for you, and
1:05
then there is a check mark saying
that this worked for that person.
1:07
So let's see if it works for us.
1:10
So it looks like you use
this Integer.parseInt.
1:12
Look there's a link to the Java Doc.
1:16
Let's go ahead and click that,
this is the actual Java documentation.
1:18
So let's see.
1:22
So it says that parseInt will return
an int, and it takes a String,
1:23
which is what we have.
1:26
This looks like exactly what we want.
1:28
Let's go ahead and
let's jump back over to our code.
1:30
And let's pull out the age from the line.
1:33
So we're gonna pull out a String first.
1:37
So we'll say console.readLine and
we know that that gives us a String.
1:39
We'll say how old are you?
1:43
Great.
So now we have ageAsString is a String
1:47
variable, so let's go ahead and let's
change this int age that we have here,
1:52
and we'll say Integer with
the capital I .parseInt,
1:57
and we'll paste on that ageAsString.
2:02
Great, and now I'm gonna save it.
2:05
And let's see if that worked.
2:07
File and run.
2:12
And it says how old are you?
2:14
So let's try and
make sure that it fails and say 10.
2:15
Great, that worked.
2:18
Let's go again one more time And remember
we said, so if they're older than 13.
2:20
So let's go and say they we're 15.
2:25
Excellent, it started working.
2:28
So, if you're in a program
that's executing like this,
2:29
you can always press Control-C and
it will stop.
2:33
Great job leaning on the Internet.
2:37
We now know how to parse
Integers out of Strings.
2:39
This is also referred to as
converting a String to an Integer.
2:42
Switching between types is
also often called casting,
2:47
which we'll cover in a future course.
2:50
You also did a great job ignoring the fact
that we introduced a new class Integer
2:52
with a capital I.
2:57
In the past, we were using the all
lowercase primitive data type int.
2:59
We used the new Integer
class's static method parseInt
3:04
to generate a primitive int.
3:08
This capital I Integer here is what is
known as a wrapper type, or a boxed type.
3:11
And what it does for
3:16
us is it provides some methods that we can
use to manipulate and produce Integers.
3:17
Remember, primitive data
types do not expose methods.
3:22
So there are these wrapper classes for
every one of the primitive data types.
3:26
Again, the other data type that we had
worked with in the past was String.
3:30
We're going to need to explore the methods
available to us because I'd also like to
3:34
do something about those names I was
being called during our beta test.
3:38
But first,
let's do an exercise on parsing Integers.
3:42
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