Assignemnt #74 and Safe Square root

Code

    
   ///name: nick cerdan
    ///period: 6
    ///program name: Safe Square root
    ///file name: SSRoot.java
    ///date finished: 10/27/15
    
    import java.util.Scanner;
    
    public class SSRoot
    {
        public static void main(String[] args)
        {
            Scanner keyboard = new Scanner(System.in);
             
            double input, sroot;
            
            System.out.println("SQUARE ROOT!");
            System.out.print("Enter a number: ");
            input = keyboard.nextDouble();
            
            while (input < 0)
            {
                System.out.println("You can't take the square root of a negative number!");
                System.out.print("Try again: ");
                input  =keyboard.nextDouble();
            }
            
            sroot = Math.sqrt(input);
            
            System.out.println("the square root of " + input + " is " + sroot );
        }
    }