Java: Reverse an integer number

Last update on May 15 2025 13:08:38 (UTC/GMT +8 hours)

Reverse an Integer

Write a Java program to reverse an integer number.

Sample Solution:

Java Code:

public class Example6 {
   public static void main(String[] args) {
	int num =1287;   
	int is_positive = 1;
        if (num < 0) {
            is_positive = -1;
            num = -1 * num;
        }
        int sum  = 0;
        while (num > 0) {
            int r = num % 10;
            
            int maxDiff = Integer.MAX_VALUE - sum * 10;
            if (sum > Integer.MAX_VALUE / 10 || r > maxDiff) 
				System.out.println("Wrong number");;
            
            sum = sum * 10 + r;
            num /= 10;
        }
        System.out.println(is_positive * sum);
   }
}

Sample Output:

7821

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to reverse an integer without converting it to a string, using arithmetic operations.
• Write a Java program to reverse an integer recursively and then verify if it is a palindrome.
• Write a Java program to reverse an integer by iteratively extracting its digits with modulus and division.
• Write a Java program to reverse an integer and compare the reversed value with the original to determine symmetry.

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