Java Question - Reversing user input

#1 · 09-10-2013 03:26PM #1

Hi there,
I am currently attending a Java course in Fás and I am having trouble with a particular question.

This is the Question:
"I need to reverse user input, without using StringBuilder".
We haven't covered it yet and I want to wait for the Instructor to explain it to us.

I would ask the instructor but a lot of times I am even more confused after!
If anyone could help me it would be great.

NOTE: I don't necessarily want the answer, what I would like is someone to explain it to me.

Thank you very much.

CreepingDeath · 09-10-2013 03:37PM

You can use a for-loop to run through the characters from the end backwards to the beginning and add them to a new string.
That will reverse the string from eg "ABCDE" to "EDCBA"

mad turnip · 09-10-2013 03:42PM

We had this question before in an interview and the girl literly submitted:

new Stringbuilder(str).reverse()

I couldn't stop laughing, there was another similar question of sorting a list and in that one she did:

Collections.sort(list);

I still can't stop laughing at it. And it was so cheeky she got the job!!!!!!!!!!!!

ChRoMe · 09-10-2013 03:44PM

mad turnip wrote: »

We had this question before in an interview and the girl literly submitted:

new Stringbuilder(str).reverse()

I couldn't stop laughing, there was another similar question of sorting a list and in that one she did:

Collections.sort(list);

I still can't stop laughing at it. And it was so cheeky she got the job!!!!!!!!!!!!

Why wouldn't she say that, its a completely valid and correct answer. The **** up is on the interviewer not defining the question correctly.

mad turnip · 09-10-2013 03:46PM

ChRoMe wrote: »

Why wouldn't she say that, its a completely valid and correct answer. The **** up is on the interviewer not defining the question correctly.

I agree completly! One would kind of presume not to do that but still funny!

onemorechance · 09-10-2013 08:25PM

Find length of user input string
Use this to find last character
Minus by one to find second last character
Repeat until you reach first character

carlmango11 · 10-10-2013 11:42AM

CreepingDeath wrote: »

You can use a for-loop to run through the characters from the end backwards to the beginning and add them to a new string.
That will reverse the string from eg "ABCDE" to "EDCBA"

Wouldn't this be inefficient because Strings are immutable?

Internally the computer would make a whole new string for:

"E"
"ED"
"EDC"
"EDCD"
"EDCDA"

Maybe building a String from a char array of the reversed String would be better

CreepingDeath · 10-10-2013 11:49AM

carlmango11 wrote: »

Maybe building a String from a char array of the reversed String would be better

Well I didn't want to give the complete solution, just pseudo-code.

Although using StringBuffer would be better again to build the new string.
They only stopped them from using StringBuilder because it has a reverse() method in there already.

Umekichi · 10-10-2013 11:54AM

Thanks guys, solved it

carlmango11 · 14-10-2013 11:32PM

CreepingDeath wrote: »

They only stopped them from using StringBuilder because it has a reverse() method in there already.

Yeah, stupid though because in the real world StringBuilder would be the way to go. They should really have just said you can't use StringBuilder.reverse

Tar.Aldarion · 16-10-2013 01:54PM

then they ask you to recursively do it, good times.

Java Question - Reversing user input

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