code: private void tryRegisterJava8Optionals() {
          try {
              loadType("java.util.OptionalInt");
              @SuppressWarnings("unchecked")
              Class<?> cls1 = (Class<TypedStringConverter<?>>) loadType("org.joda.convert.OptionalIntStringConverter");
              TypedStringConverter<?> conv1 = (TypedStringConverter<?>) cls1.getDeclaredConstructor().newInstance();
              registered.put(conv1.getEffectiveType(), conv1);
  
              @SuppressWarnings("unchecked")
              Class<?> cls2 = (Class<TypedStringConverter<?>>) loadType("org.joda.convert.OptionalLongStringConverter");
              TypedStringConverter<?> conv2 = (TypedStringConverter<?>) cls2.getDeclaredConstructor().newInstance();
              registered.put(conv2.getEffectiveType(), conv2);
  
              @SuppressWarnings("unchecked")
              Class<?> cls3 = (Class<TypedStringConverter<?>>) loadType("org.joda.convert.OptionalDoubleStringConverter");
              TypedStringConverter<?> conv3 = (TypedStringConverter<?>) cls3.getDeclaredConstructor().newInstance();
              registered.put(conv3.getEffectiveType(), conv3);
  
          } catch (Throwable ex) {
              if (LOG) {
                  System.err.println("tryRegisterOptionals: " + ex);
              }
          }
      }
docs: Tries to register the Java 8 optional classes.