example.java


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import java.util.Optional;

class Example {
  public static void main(String[] args) {
    /* should print Hi */
    Optional<String> a = Optional.of("Hi");
    System.out.println(StOptional.reduce(a));

    /* should print null */
    Optional<String> b = Optional.empty();
    System.out.println(StOptional.reduce(b));

    /* should print null */
    Optional<String> c = null;
    System.out.println(StOptional.reduce(c));
  }
}

/**
 * Stop Optionals from being used!
 * safely reducing optionals back to their original types.
 */
final class StOptional {
  /**
   * Reduce any optional down to it's original type
   *
   * @param o Optional<?> to reduce
   * @return <?> value of optional
   */
  public static final <T> T reduce(Optional<T> o) {
    return nullish(o) ? null : o.get();
  }

  /**
   * Checks if Optional<?> is null or empty
   *
   * @param o Optional<?>
   * @return boolean true if null or empty, false otherwise
   */
  public static final boolean nullish(Optional<?> o) {
    if (o == null || o.isEmpty())
      return true;
    return false;
  }
}