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Errors
4:39Errors are bound to happen. In this video we discuss what to do when they occur.
I've got some really bad news for
you, you aren't perfect.
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None of us are.
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You're gonna make mistakes.
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In fact,
I'm still constantly making mistakes.
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There are gonna be errors in your code.
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There are going to be lots
of errors in your code.
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In fact, [LAUGH] any time
you watch someone coding and
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are impressed by their lack of mistakes,
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is almost certainly because they spent
a lot of time making mistakes and they've
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learned to avoid the common pitfalls
that we all, as developers, fall into.
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The sooner you can view mistakes and
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errors as a positive result of your own
experimentation, the quicker you will be
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on the road to mastering a language and
with much less frustration.
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Remember, if you aren't failing,
you aren't learning.
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There are different types of errors.
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The most common errors
are syntax errors and
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they can be very frustrating as
you're first diving into a language.
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The good news is that Java compiler
is very good at reporting these,
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and usually, the answer is pretty clear.
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Now, let's go break stuff.
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Hopefully, you haven't had any errors yet.
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Let's intentionally make one.
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I'm gonna misspell
the string declaration here,
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making it spelled as the popular singer,
Sting.
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Let's see what happens.
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Now press the up arrow and
get our information back here.
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And we will see here that we got
an error that says, cannot find symbol.
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And if you look, this shows the line
number which is 13, line 13,
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and it says the error, cannot find symbol.
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And then also underneath here there's
an arrow that's pointing up exactly where
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the problem is.
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So that is wonderful, but now you saw
me make the change from string, but
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if you didn't and if for some reason you
didn't see the obvious arrow pointing
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at the lead singer of the Police,
one place we could turn is the Internet.
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Java's been around for a long time.
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It'll be hard to stump
Google with a Java problem.
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It's heard them all.
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Let's give it a spin.
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I'm gonna copy this,
cannot find symbol error,
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then I'm gonna swing over to Google and
I'm gonna paste that.
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So we got some results here,
we have 482,000 results.
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Let's go ahead and
look at the first one here.
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I'm feeling lucky.
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Okay, when a Java program
is being compiled,
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the compiler creates a list
of identifiers to use.
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If it can't find what an identifier refers
to, it can't complete the compilation.
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This is what we're seeing,
this is what the cannot
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find symbol error message is saying,
that's what we're getting, so it doesn't
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have enough information to piece together
what the Java code wants to execute.
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Okay, so some possible causes, trying
to use a variable without declaring it.
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Well, that's not the case cuz
that our declaration line.
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Misspelling a class or method name,
possible that we misspelled.
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Let's go back and take a,
that's right, we did misspell it.
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So let's go ahead and
put an r back in there.
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Okay, so there's an example
of a cannot find symbol.
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Another one that is very common is this,
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if we make this a lowercase s here
on the String, then we'll save this.
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Let's go ahead and I'll run it again.
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Okay, we get a cannot find symbol in its
own string, a string is spelled right, so
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let's go ahead let's jump back over there.
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Let's search for that specifically.
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So we have cannot find symbol in string.
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Okay, so 998,000 results here.
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I scroll down and I see,
well, this one's from Oracle.
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That's great cuz Oracle's the company
that currently makes Java so
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let's take a look and
see what they have to say here.
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This person is having
a similar problem that we are.
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Java file's not recognizing
string as in private string name.
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What is going on and
could this be an install problem?
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Capital letter S.
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Everything in Java's case sensitive,
okay, great.
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So let's go back and we can fix that.
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Perfect.
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So that's an example of what you
can do when you get an error.
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Remember, just go out and search for it,
come to the forums if you need to as well.
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So now we know that we will make syntax
errors and what they'll look like.
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I'll show off some more
common gotchas in logic and
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other runtime errors as we dig
a little deeper into our program.
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I've pointed out the seemingly
endless resources on the Internet, but
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I want to encourage you once again to use
the treehouse community to your advantage.
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Your fellow classmates are here to
help and by sharing your errors,
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it actually gives someone else
the ability to learn from your mistakes.
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