Reverse number after inputting an integer and doubling it

the directions are the following: input an integer, then double integer value, then call your static void reverse( long i ) method. The method void reverse( long i) displays the 开发者_如何学编程integer in reverse terminated by a new line.

I need help in reversing the integer. I think I have the rest of the code correctly. But, correct me if I'm wrong.

    import java.util.Scanner;

public class Exercise5_3M {
    public static void reverse(String[] args) {
    Scanner input = new Scanner(System.in);

    //input an integer
    int num= input.nextInt();
    int result=0;

     //Double the intger
    while(num>0){
    result= num *2;

        }


System.out.print(result);
    }
}

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at first of all you need void reverse( long i) instead void reverse(String[] args) at second

while(num>0){
    result= num *2;
}

never end, because num never change

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Your method should be called "main" when you want to execute it on start. Second you created an infinity loop with your while when sb enters a positive number. A negative always returns 0. Third you have no method called reverse(long i). Fourth boundary check. Are only positive numbers allowed or negative also?

For a tip: You can reverse it in multiple ways. Convert your number to a string or char array and reverse it. Or you want to have a look at the mod operator "%".