Java Throwing Exceptions - Exercise Result

classSqRoot2 {
 public static void main(String[] args) {
  try {
   double d = getInput(args[0]);
   double root = Math.sqrt(d);
   System.out.println("The square root of " + d + " is " + root);
  }
  catch(NumberFormatException e) {
   System.out.println("Be sure to enter a number.");
  }
  catch(ArrayIndexOutOfBoundsException e) {
   System.out.println("Enter number as 1st parameter.");
  }
  catch(ImNumberException e) {
   System.out.println("Result will be imaginary number.");
  } 
 }
 static double getInput(String s) throws ImNumberException {
  double d = new Double(s).doubleValue();
  if (d < 0)
   throw new ImNumberException();
  return d;
 }
}
classImNumberException extendsException {}