In this program we will reverse a number in java using for loop , while loop and recursion .Reversing a number means swap first element with last element and second element with second last element and so on till the middle element . In this article we will see various ways for java program to reverse a number as following .
1. Reverse a Number using while loop 2. Reverse a Number Using For loop 3. Reverse a Number Using Recursion
Reverse a Number Using while loop
Now we will write a program in java to reverse the digits of a number using while loop . In this program first we will add reminder of number num in reverse which is initialize by zero .In second step we will assign value of num/10 to number num and so on.
public class ReverseNumber {
public static void main(String[] args) {
int num = 251;
int reverse = 0;
while (num > 0) {
reverse = reverse * 10 + num % 10;
num = num / 10;
}
System.out.println("reverse number is =" + reverse);
}
}Output:
reverse number is =152Reverse a Number Using For loop
We will write a program to reverse a number in java using for loop. We will use same logic as above only replace while loop with for loop.
public class ReverseNumber {
public static void main(String[] args) {
int num = 251;
int reverse = 0;
for ( ; num != 0 ; num/=10) {
reverse = reverse * 10 + num % 10;
}
System.out.println("reverse number is =" + reverse);
}
}Output:
reverse number is =152We have written programs to reverse a number in java without using built in methods. We have used loop to reverse the number in java . In next way we see how to reverse a number in java without using loop .
Reverse a Number Using Recursion
Now we will reverse a number using recursion in java .
public class ReverseNumberByRec {
public static void main(String[] args) {
int num = 251;
System.out.println("reverse number is =" + reverseNumber(num));
}
static int reverse = 0;
private static int reverseNumber(int num) {
if (num > 0) {
reverse = reverse * 10 + num % 10;
reverseNumber(num /= 10);
}
return reverse;
}
}Output:
reverse number is =152In this article we have seen various program to reverse a number in java . You can see Top java coding programs with answer. You can learn also how to reverse string in java with good example.