Validating input using java.util.Scanner [duplicate]

Answer 1

If you are parsing string data from the console or similar, the best way is to use regular expressions. Read more on that here: http://java.sun.com/developer/technicalArticles/releases/1.4regex/

Otherwise, to parse an int from a string, try Integer.parseInt(string). If the string is not a number, you will get an exception. Otherise you can then perform your checks on that value to make sure it is not negative.

String input;
int number;
try
{
    number = Integer.parseInt(input);
    if(number > 0)
    {
        System.out.println("You positive number is " + number);
    }
} catch (NumberFormatException ex)
{
     System.out.println("That is not a positive number!");
}

To get a character-only string, you would probably be better of looping over each character checking for digits, using for instance Character.isLetter(char).

String input
for(int i = 0; i

Good luck!