In this Java program, you’ll learn how to reverse a number. This post explains two ways to reverse a number: while
and for
loop
Here are the examples to reverse a number in Java.
Algorithm to reverse digits of a number
digit = num%10;
reversedNum = (reversedNum * 10) + digit;
num = num/10;
In this program, you will see how to reverse a number using a while
loop.
//Java Program to Reverse a Number using While Loop
import java.util.Scanner;
public class JavaPrograms {
public static void main(String[] args) {
int reversedNum = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Enter a number: ");
int num = sc.nextInt();
// closing scanner class(not compulsory, but good programming practice)
sc.close();
// run loop until num becomes 0
while (num != 0) {
// get last digit from num
int digit = num % 10;
reversedNum = reversedNum * 10 + digit;
// remove the last digit from num
num /= 10;
}
System.out.println("Reversed Number: " + reversedNum);
}
}
Enter a number:
5245
Reversed Number: 5425
In this program, you will see how to reverse a number using a for
loop.
//Java Program to Reverse a Number using For Loop
import java.util.Scanner;
public class JavaPrograms {
public static void main(String[] args) {
int reversedNum = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Enter a number: ");
int num = sc.nextInt();
// closing scanner class(not compulsory, but good programming practice)
sc.close();
for (; num != 0; num /= 10) {
int digit = num % 10;
reversedNum = reversedNum * 10 + digit;
}
System.out.println("Reversed Number: " + reversedNum);
}
}
Enter a number:
85658541
Reversed Number: 14585658
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