Why am I all of a sudden getting a Input/Output error?

public class Example {

    public static void main(String[] args) {
        // Your amazing code goes here...
        System.out.println("We are making a new Pez Dispenser.");
        PezDispenser dispenser = new PezDispenser("Yoda");
        System.out.printf("The dispenser character is %s %n",
                          dispenser.getCharacterName());
        if (dispenser.isEmpty()) {
          System.out.println("It is currently empty");
        }
        System.out.println("Loading...");
        dispenser.load();
        if (!dispenser.isEmpty()) {
           System.out.println("It is no longer empty.");
        }
        while (dispenser.dispense()) {
          System.out.println("Chomp!");
        }
        if (dispenser.isEmpty()){
          System.out.println("Ate all the PEZ!");
        }
        dispenser.load(4);
        dispenser.load(2);
        while (dispenser.dispense()) {
          System.out.println("Chomp!");
        }
      dispenser.load(400);
      System.out.println("This will never happen");
    }
}

public class PezDispenser {

  public static final int MAX_PEZ = 12;

  private String mCharacterName;
  private int mPezCount;

  public PezDispenser(String characterName) {
    mCharacterName = characterName;
    mPezCount = 0;
  }

  public boolean dispense() {
    boolean wasDispensed = false;
    if (!isEmpty()) {
      mPezCount--;
      wasDispensed = true;
    }
    return wasDispensed;
  }

  public boolean isEmpty() {
    return mPezCount == 0;
  }

  public void load() {
    load(MAX_PEZ);
  }

  public void load(int pezAmount) {
    int newAmount = mPezCount + pezAmount;
    if (newAmount > MAX_PEZ) {
      throw new IllegalArgumentException("Too many PEZ!!!");
    }
    mPezCount = newAmount;
  }

  public String getCharacterName() {
     return mCharacterName;
  }
}