Exception in thread java programming error

Question

I am trying to run a java program to find if number is palindrome or not but at the time of compilation i am getting error message as - Exception in thread "main" java.lang.Error: Unresolved compilation problem: This method must return result of type Boolean.

below is my program code :

package testing;
import java.util.Scanner;
public class PalindromeNumber { 
    public static void main(String[] args) {
        System.out.println("Enter a number to check if it is palindrome or not :");
        int number1 = new Scanner (System.in).nextInt();
        if(PalindromeCheck(number1)) {
            System.out.println("Number " +number1+ " is palindrome.");
        }
        else {
            System.out.println("Number " + number1 + " is not palindrome.");
        }
    }




public static boolean PalindromeCheck(int number) {
    int palindrome = number;
    int reverse = 0;
    while (palindrome !=0) {
        int remainder = palindrome % 10;
        reverse = reverse * 10 + remainder;
        palindrome = palindrome / 10;
        if (number == reverse) {
            return true;
        }

    return false;
}
}
}

Put one of the 3 ending curlybraces before the Line 'return false;' — Pras
– Pras, Commented Jun 11, 2016 at 4:54
Thanks @Pras. It worked. can you please tell me what my mistake was ? — Akshay Jadhav
– Akshay Jadhav, Commented Jun 11, 2016 at 4:56
From what I see it doesn't look like you're working in an IDE. While I can't force you to, I do recommend you switch to one. An IDE can resolve and identify problems for you, as well as provide suggestions to help you code faster. — parabolah
– parabolah, Commented Jun 11, 2016 at 5:00
Your mistake was failing to include a required ending brace in the correct place, followed by ignoring a compiler error message and attempting to execute the resulting invalid class. As @WinterRoberts says, use an IDE, Eclipse or NetBeans if you want a free one. — Jim Garrison
– Jim Garrison, Commented Jun 11, 2016 at 5:00
The curly brace i asked u to move is the "end" of while loop : you were returning false in the loop actually — Pras
– Pras, Commented Jun 11, 2016 at 5:00

Imesha Sudasingha · Accepted Answer · 2016-06-11 04:56:52Z

1

What if the number=0 at the begining? Your code won't return anything at that moment. Return false, outside the while loop.

public static boolean PalindromeCheck(int number) {
    int palindrome = number;
    int reverse = 0;
    while (palindrome !=0) {
        int remainder = palindrome % 10;
        reverse = reverse * 10 + remainder;
        palindrome = palindrome / 10;
        if (number == reverse) {
            return true;
        }
    }
    return false; //Note the curly brace above. Now the method will always return either true or false
}

answered Jun 11, 2016 at 4:56

Imesha Sudasingha

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Comments

Priyansh Goel · Accepted Answer · 2016-06-11 04:59:06Z

1

public static boolean PalindromeCheck(int number) {
    int palindrome = number;
    int reverse = 0;
    while (palindrome !=0) {
        int remainder = palindrome % 10;
        reverse = reverse * 10 + remainder;
        palindrome = palindrome / 10;
        if (number == reverse) {
            return true;
        }

    return false;
}
}
}

In this case, while loop also includes return false. So, in the case when while loop is completed , you don't have a return value. So, the following will work:

public static boolean PalindromeCheck(int number) {
    int palindrome = number;
    int reverse = 0;
    while (palindrome !=0) {
        int remainder = palindrome % 10;
        reverse = reverse * 10 + remainder;
        palindrome = palindrome / 10;
        if (number == reverse) {
            return true;
        }
    }

    return false;

}
}

edited Jun 11, 2016 at 4:59

answered Jun 11, 2016 at 4:56

Priyansh Goel

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2 Comments

Akshay Jadhav Over a year ago

Thanks @Priyansh Goel

Priyansh Goel Over a year ago

@AkshayJadhav : Please accept the answer <Click on tick to accept>

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