Fluent APIs to prevent NullPointerException

fluent1.Consumer.java

public class Consumer implements UserAPIConsumer {
  @Override
  public void doit(UserAPI userAPI) {
    userAPI.withCurrentOrNextPeriod(new BillingPeriodContext() {
      @Override
      public void executedIfPeriodExists(BillingPeriod period) {
        System.out.println("yes: " + period);
      }
      @Override
      public void executedOtherwise() {
        System.out.println("no: no period available");
      }
    });
  }
}

fluent1.UserAPI.java

public interface UserAPI {
  /**
   * Invokes the corresponding method on the supplied context.
   */
  void withCurrentOrNextPeriod(BillingPeriodContext context);
}

public interface BillingPeriodContext {
  void executedIfPeriodExists(BillingPeriod period);
  void executedOtherwise();
}

nullable.Consumer.java

public class Consumer implements UserAPIConsumer {
  @Override
  public void doit(UserAPI userAPI) {
    Nullable<BillingPeriod> periodRef = userAPI.getCurrentOrNextPeriod();
    if (periodRef.hasValue()) {
      System.out.println("Yay: " + periodRef.getValue());
    }
  }
}

public class BadConsumerStillPossible implements UserAPIConsumer {
  @Override
  public void doit(UserAPI userAPI) {
    Nullable<BillingPeriod> periodRef = userAPI.getCurrentOrNextPeriod();
    System.out.println("Hmm, still skipping null check: " + periodRef.getValue());
  }
}

nullable.Nullable.java

public interface Nullable<T> {
  /**
   * Returns true if it's safe to call {@link #getValue()}.
   */
  boolean hasValue();

  /**
   * Throws a runtime exception if called when 
   * {@link #hasValue()} would return false.
   */
  T getValue();
}

nullable.UserAPI.java

public interface UserAPI {
  /**
   * Returns the current or next billing period, 
   * if one's available.
   */
  Nullable<BillingPeriod> getCurrentOrNextPeriod();
}

nullable.UserAPIConsumer.java

// same as original/first version
/**
 * An API consumer may implement this to use the UserAPI.
 */
public interface UserAPIConsumer {
  void doit(UserAPI userAPI);
}

original.UserAPI.java

public interface UserAPI {
  /** 
   * Returns true if the user has a current or next 
   * billing period.
   */
  boolean userHasCurrentOrNextBillingPeriod();

  /**
   * Returns the current or next billing period, 
   * if one's available.
   */
  BillingPeriod getCurrentOrNextPeriod();
}

original.UserAPIConsumer.java

/**
 * An API consumer may implement this to use the UserAPI.
 */
public interface UserAPIConsumer {
  void doit(UserAPI userAPI);
}