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AP Computer Science A Videos 108 videos
AP Computer Science 1.2 Program Development. Which of the following is correct?
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AP Computer Science 2.4 Review of the Basics 195 Views
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Description:
APCS: Review of the Basics Drill 2, Problem 4. What is the output of the following code segment?
Transcript
- 00:00
Sorry And here's your smoke du jour courtesy of escaped
- 00:06
character whether it's hannibal lecter breaking out of prison or
- 00:10
a quotation mark escaping the tyranny of java syntax escaped
- 00:14
characters make everything more interesting All right what is the
- 00:18
output of the following code segment Things work right here
Full Transcript
- 00:23
and here the potential answers All right pausing thinking and
- 00:28
we're going to answer this question We need to know
- 00:31
what exactly an escape character or escape sequence is And
- 00:36
when it's used Well this is one of those things
- 00:38
that doesn't get used frequently but when you need it
- 00:41
you'll wonder how you would have managed without it Yeah
- 00:44
like knowing how to catch a fish with your shoe
- 00:46
laces but not quite as dramatic In java a backslash
- 00:49
followed by a certain character is called in escape sequence
- 00:53
Let's suppose you want to print the following string in
- 00:56
a program The sign at the door red no hats
- 00:59
please but i wasn't technically wearing a hat It was
- 01:01
a raccoon not wanting to cause trouble mr scratchy and
- 01:04
on a left the interesting program you've got there The
- 01:08
problem with throwing that string in a normal print statement
- 01:11
is the quotation marks will confuse the compiler It believes
- 01:15
the first quotation mark from no hats please is the
- 01:18
end of the print statement after that it's expecting to
- 01:22
see more code and when that doesn't happen the compiler
- 01:25
will return an error There are a couple ways to
- 01:28
solve this problem First one would be tio not where
- 01:31
raccoon is a hat because second and more useful way
- 01:35
would be to escape the quotation marks in the string
- 01:40
So the compiler doesn't treat him like a code really
- 01:43
by placing a backslash in front of the quotation marks
- 01:45
we want to compiler to ignore We escape them and
- 01:49
they'll get asked like right through the prince stay just
- 01:52
like that though notice that we use the back slash
- 01:55
on the apostrophe too that's to prevent it from being
- 01:58
recognized as a single There are some special escape sequences
- 02:02
to a backslash followed by an end will insert a
- 02:05
new line at that position Backslash t will insert tab
- 02:09
and there are a few others that are a little
- 02:11
more obscure like this stuff Our question is asking us
- 02:15
what will happen with the following print statement so let's
- 02:18
look at the back slashes in the string The first
- 02:21
one will ensure the apostrophe gets past and not confused
- 02:24
for code So time will come out just fine Quotation
- 02:28
marks around testing are also properly escape so those quotation
- 02:32
marks will be printed correctly Then there's the backslash end
- 02:35
which is we just learned prints a new line and 00:02:38.63 --> [endTime] that's answered
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