However, the only language you mentioned was Java, so I assumed that was what you were working in. Now, I see that you also mentioned .NET, which still does not pin down a single language, but I also realise there is no Java.NET due to some law suits Microsoft lost even before .NET was cooked up.

Thank you for that thoughtful comment.

In C# strings are objects as well, but with a special caveat: its == operator is overloaded to perform a .Equals() comparison instead of an address comparison.

This ensures that someString == someOtherString will compare string values.

Inefficient code isn’t wrong unless a good/the best/a certain speed was a requirement stated in the question, so to me it makes little sense that you were shown the door over that little issue.

However, if I were your interviewer, I would most definitely show you the door if you showed me that exact code, as there is a major problem with it. A problem that makes your code plain wrong: string comparison.

In Java, strings are objects, not primitives (magical objects, but objects nevertheless) and in Java, if you use “==” to compare two objects, you won’t actually compare the two objects, but you will compare the addresses of the objects. To actually understand that it helps to have some lower level language experience (eg C) and know how Java behaves in relation to it, but it is a fact that if you are learning Java and you come to the subject of strings, one of the first things you will be taught is that you should not compare string using “==”.

The thing is, the code might appear to work. This is because of how Java works _internally_. To save memory, it might not make a new string if both strings contain the same contents, in which case the “==” will indeed give the expected result. However, it gives no promise as to such behavior, so it might just as well make a new string (if not now, perhaps in a future version of Java), so the function you gave might just as well return that the string is not a palindrome, even if it is.

Simply said, the provided function _might_ work as you expect, but it doesn’t _have_ to, so it’s just plain wrong. No sense talking about the efficiency of your code if there is such a major flaw in it…

-disclaimer-
If you the code you gave here does not match up with the code you gave your interviewer, this whole rant makes no sense at all, but it should just match up. Honestly, though, it makes a whole lot of sense to me if that error was the reason you were shown the door, seeing that an inefficiency would not exactly constitute much of a reason to be _that_ convinced you aren’t qualified for the job…