Code correction suggestion using Java libraries for strings?

Question

I know there is an easier way of making things work to check whether a string is a palindrome or not, but I wanted to try it using library functions and I came up with the code below.

public boolean isPalindrome1(String input)
{

    int length = input.length()/2;
    if(input.length()%2!=0)
    {
        length = length + 1;
    }


    return(input.substring(0,length).equals(new StringBuilder(input.substring(length, input.length())).reverse().toString()));
}

I'm trying to check whether half the string is equal to the other half's reverse. But it is getting messed up for odd and even lengths. Can someone point corrections in this where it will work for odd, even lengths as well as empty string and string of length = 1.

Why half? You won't get any noticeable performance improvements over the whole string (which avoids the odd/even problem) — SomeKittens
– SomeKittens, Commented Aug 2, 2012 at 16:34
But with splitting how will it work ? I will not use the code but am just curious to know how to solve for this case. — Phoenix
– Phoenix, Commented Aug 2, 2012 at 16:41
There's no need to solve a hard problem if there's an easier way to do it. "Solving for this case" in my book is using the simple solution. — SomeKittens
– SomeKittens, Commented Aug 2, 2012 at 16:49
@SomeKittens you should know each and every possible way to solve a problem — Harmeet Singh
– Harmeet Singh, Commented Aug 2, 2012 at 17:11

Carl · Accepted Answer · 2012-08-02 16:34:53Z

6

You're already using reverse(). Why can you not compare the input String with the reverse? Isn't that exactly what you're wanting in the first place? No need to be splitting things in half in a complicated way.

answered Aug 2, 2012 at 16:34

Carl

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Harmeet Singh · Accepted Answer · 2012-08-02 17:09:04Z

2

you can:

return new StringBuilder(input).reverse().toString().equals(input);

here you go as you want to know :

public boolean isPalindrome(String input) {
    for (int i = 0; i < input.length() / 2; i++) {
        if (input.charAt(i) != input.charAt(input.length() - 1 - i)) {
            return false;
        }
    }
    return true;
}

edited Aug 2, 2012 at 17:09

answered Aug 2, 2012 at 16:36

Harmeet Singh

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