CODEWITHSUNDEEP
java
Mohammad Bin Aftab
Mohammad Bin Aftab

Reputation: 1

getting an error in my palindrome java program

I have created a palindorme java program which is getting an error.the error is saying int cannot be converted to boolean.

    import java.util.Scanner;
public class palindrome
{
    public static void main()
    {
        Scanner sc = new Scanner(System.in);
        int l,i;
        String s,s1;
        System.out.println("Enter your string");
        s = sc.nextLine();
        l = s.length();
        for(i=0;l-i-1;i++)
        {
            s1 = s + s.charAt(i);
        }
        if(s1==s) 
            System.out.println("This is Palindrome");
         else
         System.out.println("This is not a Palindrome");
        }
    }

Upvotes: 0

Views: 226

Answers (3)

Nexevis
Nexevis

Reputation: 4667

There are quite a few things off here, first here is the fixed code:

public static void main(String [] args)
{
    Scanner sc = new Scanner(System.in);
    int l,i;
    String s = "",s1 = "";
    System.out.println("Enter your string");
    s = sc.nextLine();
    l = s.length();
    for(i = l - 1; i >= 0; i--)
    {
        s1 = s1 + s.charAt(i);
    }
    if(s1.equals(s)) 
        System.out.println("This is Palindrome");
    else
        System.out.println("This is not a Palindrome");
}

The first thing to fix was your for loop, as you saw you were getting an error. This was fixed by setting the initial i to the length minus 1, changing the loop condition to i >= 0, and using i-- to subtract 1 from i each loop.

These changes to the loop were made so that the character starting from the last position in the String is the first one being return by s.charAt(i) so you can reverse the String. I think you were attempting to do something along these lines to add the characters starting from the end to a String.

I also changed s1 = s + s.charAt(i) to s1 = s1 + s.charAt() so the correct String is being appended. (This should probably be StringBuilder however).

s and s1 now have the initial condition of "" instead of nothing.

And finally you cannot compare String equality with ==, it must be s1.equals(s).

Test Run:

Enter your string

racecar

This is Palindrome

Upvotes: 0

Razib
Razib

Reputation: 11163

Along with the answer above you can try a different approach. You don't need to go all the string length to check a palindrome. A palindrome can be checked iterating half of the array length like this - 

public void checkPalindrome(String strToCheck){
      char[] arr = strToCheck.toCharArray();
      int size = arr.length;
      char [] original = Arrays.copyOf(arr,arr.length);

      for (int i = 0; i < size / 2; i++) {
         char temp = arr[i];
         arr[i] = arr[size-i-1];
         arr[size-i-1] = temp;
      }

      if(Arrays.equals(arr, original)) {
         System.out.println("Palindrome");
      } else {
         System.out.println("Not a palindrome");
      }
}

What are done here:

  • reversing the string first iterating the halfway
  • comparing the reversed string with the original using Arrays.equals() method.

Upvotes: 0

hagarwal
hagarwal

Reputation: 1163

For loop condition seems wrong.

for(initial counter; condition to terminate; increase counter) {}
for(i=0; i<l; i++) {}

Upvotes: 1

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