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Description:
AP Computer Science 1.1 Standard Data Structures. Which of the following method calls will result in an error?
Transcript
- 00:00
Thank you We sneak Then here's your shmoop toos your
- 00:05
brought to you with the explicit promise that will never
- 00:09
use cow puns will milk some utter ting for humor
- 00:14
Consider the following segment of code right there This thing
- 00:17
animal equals new animal best for cab equals new count
Full Transcript
- 00:19
bessie for which of the following method calls will result
- 00:23
in an error and hear of potential answers Roman numerals
- 00:28
there Well this questions asking us about calling methods which
- 00:31
is pretty much a day to day thing in java
- 00:34
By now you've probably read a bit about classes relationships
- 00:36
and methods and could take a stab this question but
- 00:39
let's fully go over the nature of what we're dealing
- 00:41
with Imagine the following a super class vehicle which branches
- 00:45
down with a few subclass is called minivan motorcycle and
- 00:50
bicycle vehicle would contain members that could be useful tow
- 00:53
any type of vehicle number of wheels propulsion method whatever
- 00:57
you need Really the methods in the minivan class would
- 01:01
be specific to minivan objects Open sliding door full down
- 01:05
rear seats insist i am still cool it's on a
- 01:09
ce faras our question goes it's asking us which of
- 01:12
the attempts to call the method print mu will not
- 01:15
work well The question by design doesn't give us complete
- 01:19
information so we'll have to make a couple educated guesses
- 01:22
based on programming conventions for one will assume that animal
- 01:26
is a super class and that cow is a subclass
- 01:30
of it seems likely that animal and cow have an
- 01:33
inheritance or is a relationship since cow is a gn
- 01:37
animal and second will assume that print mu is a
- 01:39
method belonging to cow rather than the annals Not every
- 01:43
animal moves but most are all cows do so with
- 01:47
that in mind and with our snippet of code that
- 01:49
creates an animal object as a and a cow object
- 01:52
is b which of these attempts at calling print move
- 01:55
will not work We'll attempt one looks good b is
- 01:59
our cow object and this line calls the print moon
- 02:01
method appropriately attempt to looks a little weird What with
- 02:05
these parentheses all over the place we're casting b to
- 02:09
an animal and trying to call print move on it
- 02:12
Even though b is a cow the computer thinks it
- 02:14
is an animal because we've cast it so it'll give
- 02:18
us an error because print move doesn't exist in the
- 02:21
animal class In ten three uses object a an animal
- 02:25
without casting It is a cow so no dice there
- 02:29
One is a legal call but two and three or
- 02:31
not that means our answer is a hay If you
- 02:34
heard about the platypus that called customer service yeah he 00:02:37.935 --> [endTime] couldn't figure out why he got a bill
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