- Reviewing Our Feedback 6:11
- Conditional ints 3 objectives
- Parsing Integers 3:46
- Parsing Integers 1 objective
- Censoring Words - Using String Equality 4:51
- String Equality 2 objectives
- Censoring Words - Using Logical ORs 4:31
- Using Logical ORs and ANDs 5 questions
- Censoring Words - Looping Until the Value Passes 7:16
- Looping until the value passes 3 objectives
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Censoring Words - Looping Until the Value Passes
7:16In this video, we wrap up the course by introducing a mechanism to continually prompt until a valid response is obtained.
At the end of the last video, we talked
about how it was frustrating to do such
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a hard exit when there was a word that
was entered that we wanted to censor.
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It's probably, in fact,
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much better if we continue to prompt
the user until we get a proper value.
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This is a common pattern in programming.
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And it's usually solved using
what is known as a while loop.
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Now what happens is you run the same
code block until a certain condition
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is no longer true.
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In other words, while this
condition is true, do these things.
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Java has a nice feature called a do while,
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which allows us to first run the code
once before any live checking is done.
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Let's use the do while loop to make
sure that the user enters a valid word.
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Okay, so the first thing we wanna do is
locate the block that we wanna repeat.
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So like we said, we wanna continuously
prompt the user until we get a valid noun.
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So it looks like here is
a good place to start.
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So in order to repeat the code,
what we'll do is use the keyword do, and
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then we'll do an open bracket there,
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which that signifies that
there's a new code block coming.
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I'm gonna highlight these.
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I'm gonna press the Tab key.
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Great.
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Okay, so now what we want to do is,
we want to change the exiting text,
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because we're no longer gonna exit.
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So let's come over in here, and
we'll change this to say try again,
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and then we'll get rid of the System.exit,
because there's nowhere we're gonna exit.
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Okay.
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So next what I'm gonna say now,
because we're in the do loop code book,
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and then we're going to put in while.
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All right and so now, we are gonna loop
while these things are invalid, so
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we already have a statement for
this which is that and I will do, and
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then we'll do this and
we'll end in semi colon.
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All right.
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Now I hope that is starting
to feel wrong to you, and
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that you just I thought that said wait
a second, you said don't repeat yourself.
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Well don't worry,
we'll fix that in the minute.
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So in addition to repeating ourselves, I
just introduced a bug into this code, but
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I want you to experience it as it's
very common and knowing how and
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why to fix it will save you loads of time.
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Okay, so let's go ahead and
save this and let's compile it, and
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we'll get an error here.
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OK, so it says error cannot find symbol,
and it's pointing here to noun.
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That's interesting cause we very clearly
define noun here and set right here,
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set inside of this block
instead of this two block here.
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The problem arises,
because of something called scope.
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Every time we open up a block of code,
like we do right here.
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It opens up a new variable scope and
code run outside of the scope.
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So see here's the closing here, and
here's the noun that we're using and
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see it's outside of that scope.
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So everything that runs outside
of that scope can't see
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the variables declared inside.
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Now the reason for this, and why you might
want to use this is a more advanced topic.
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And we'll get into that
later in a further course.
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But for now, I'd like to assist
you in solving the current problem
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of the outer scope not
knowing about the variable.
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And it's actually pretty easy.
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What we want to do is we just want
to declare the variable outside.
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So we'll say String noun.
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And then we want to remove
the declaration here,
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because we want it to be talking
about the same variable.
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All right?
So declare it here, and
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then we'll use it here.
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Okay, so let's try that out.
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I'm gonna save.
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Let's compile and run.
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Great.
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Okay, so let's see, dork, the language
is not allowed, I'll try again.
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Jerk, no?
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Awesome.
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Okay so now back to that bad practice
we introduced of repeating ourselves.
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So what tool do we use when we want
to store a value and reuse it?
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That's right, a variable.
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We can evaluate and store the results of
the condition that's in the if statement
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and store that in a variable.
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As we said earlier that's
called a boolean value.
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A boolean is a primitive data type and
it starts true or false, and
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it uses the lower case convention.
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Let's declare our variable.
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That's boolean isInvalidWord
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equal, I'm wanna go ahead and
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use the same trick that we did
before with the parenthesis.
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So I'm gonna copy that.
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Same here.
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See if we can make that
look a little bit cleaner.
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That looks pretty good.
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So now we can use the boolean.
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We can say if is invalid word,
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we can use that boolean here
that code that we duplicated.
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And we also notice something else.
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We notice we're defining
inside of the scope here.
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We're defining a boolean, but when we
are using it outside of the code block.
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What do we do?
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We're going to go ahead and do what we
just learned and move this boolean,
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put it up here.
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Great.
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Go ahead and save, compile,
let's make sure things are still working.
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Great it is excellent.
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I think we have a fully
censorship ready prototype.
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Awesome job adding loops to your skillset.
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Now we know how to continuously run our
code until a specific condition is met.
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I'm certain that you'll end up
using this pattern quite a bit.
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We also learned that we can use a do while
loop to make sure that the code runs at
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least once first before looping.
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There are other types of loops that
will investigate in future projects, but
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the basic idea is the same for
all of them.
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We store the results of a condition in a
boolean variable, so that we can reuse it
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and not repeat ourselves in code,
and thus keeping things dry.
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We came up with a user
friendly way to censor input,
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without causing the users to restart or
lose data.
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I'm quite happy with where we ended
up after soliciting feedback from
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our beta testers.
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I'd like to congratulate you here.
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We have a working prototype.
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I'd like to encourage you to show it
off to your family and your friends.
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You should practice by
making the story longer.
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Add different parts of speech and
experiment with other ways of censoring.
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Share your findings with the community.
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I've added a couple of suggestions of
directions that I'd like you to explore in
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the teacher's notes.
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There are better ways to solve some of the
problems that you're likely to run into.
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We just haven't gone over them yet.
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But the point is this, you created
a working application, and you immersed
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yourself in the Java language,
and you did an awesome job at it.
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I hope you had a fun time doing it.
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I look forward to walking through our
next problem introducing you to more and
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more tools and concepts.
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Thanks again for hanging out,
and I'll see you next time.
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After the exercise of course,
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you didn't think I was going to let
you go without a challenge did you?
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