title: Detecting empty input (JAVA)
body: <p>So my program has to count the amount of change a person enters in the scanner method, however, two errors must pop out if a) the input is not a number and b) if the input is lacking. I am having a lot of trouble with the latter. </p>
  
  <pre><code>import java.util.InputMismatchException;
  import java.util.Scanner;
  public class MakingChange 
  {
  public static void main(String[] args)
  {
  
      Scanner input = new Scanner(System.in);  // Reading from System.in
      System.out.print("How much money do you have: ");
  
      double amountInDollars = 0;
  
          try {
                  amountInDollars = input.nextDouble();
          } catch (InputMismatchException e) {
                  System.out.println("INVALID"); //print invalid
          return;
          }
  
          if (input.equals(" ")){
              System.out.println("INVALID");
              return;
          }
  
  
          int amountInPennies = (int) Math.round(amountInDollars * 100);
          amountInPennies = (int) (Math.round(amountInPennies / 5.0)  * 5);
  
          //toonies
          int numberofToonies = (int)(amountInPennies / 200.00);
          amountInPennies = amountInPennies % 200;
          //loonies   
          int numberofLoonies = (int) (amountInPennies / 100.00);
          amountInPennies = amountInPennies % 100;
          //quarters
          int numberofQuarters = (int)(amountInPennies / 25.00);
          amountInPennies = amountInPennies % 25;
          //dimes      
          int numberofDimes = (int)(amountInPennies / 10.00);
          amountInPennies = amountInPennies % 10;
          //nickels  
          int numberofNickels = (int)(amountInPennies / 5.00);
  
  System.out.println("toonies:" + numberofToonies + ";" + " loonies:" + numberofLoonies + ";" + " quarters:" + numberofQuarters + ";" + " dimes:" + numberofDimes + ";" + " nickels:" + numberofNickels); 
  
  }   
  }
  </code></pre>
  
  <p>So the expected should be "INVALID" but currently, all that returns is a blank space. 
  Thanks!</p>