Assignemnt #74 and Safe Square Root

Code

   import java.util.Scanner;
    
    public class SafeSquareRoot
    {
        public static void main( String[] args) 
        {
        
            Scanner keyboard = new Scanner(System.in);
        
            double a, b;
        
            System.out.println( "Square Root! ");
            System.out.print( "Enter a number: " );
        
            do 
            {
                a = keyboard.nextDouble();
                if ( a >= 0 )
                {
                    b = Math.sqrt(a);
                    System.out.println( b );
                }
                else if ( a < 0 )
                {
                System.out.println(" You can't take the square root of a negative number");
                System.out.print( "Try again: " );
                }
            } 
            while ( a < 0 );
        
        }
    }
       
    

Picture of the output