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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?

Language:
English Language

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

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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