Venting - Java's Optional

After reading Matt's tip for academic blogging, I decided to hop on tip 4, Vented steam as post, and focus my concerns around the design of Java's Optional type and the capacity for misuse from junior/inexperienced Java engineers. A quick Google search for Optional misuse will render countless results. What many of these articles miss is an illustration of the common bad practices, so as a visual learner myself, I wanted to show in code what happens when you give a baby a knife. These are all examples I've seen used in production and introduced in merge requests by fairly intelligent CS graduates:

1. Null-checking

if (Optional.ofNullable(arg).isPresent()) {
  // do the thing...

Somehow, we've made null-checking even worse. Stick to the original, it's safe, people know what you're talking about, and it's shorter code to type:

if (arg != null) {
  // do the thing

2. Arguments

private static String helpfulMethod(Optional<MyClass> arg) {
  // do the thing

Don't force users to wrap everything in an Optional! The Java language authors have been quite frank that Optional was intended for use strictly as a return type, to convey that a method may or may not return a value. Instead, perform proper validations against your input, like null-checking. If not, you're forcing users to write bad code like below:

MyClass.moreHelpfulMethod(Optional.of(val0), Optional.of(val1), Optional.of(val2));

or worse...

MyClass.moreHelpfulMethod(Optional.ofNullable(val0), Optional.ofNullable(val1), Optional.ofNullable(val2));

As the author of said function, using Optional arguments forces you to check against three cases: null, non-null-without-value, and non-null-with-value, instead of two: null or a valid value.

3. Method Chaining

Optional.ofNullable(val).orElse(() -> new Value()).ifPresent(myClassInstance::setValue);

Again, stick to the fundamentals:

if (val == null) {
  val = new Value(); // Or throw an exception/error

I'm not going to start posting memory graphs on here, but resources claim that wrapping references in Optional will incur a 4x memory and GC overhead.

4. Returning Null

public Optional<MyClass> extremelyHelpfulMethod(String arg) {
  // the thing

  return null;

Let's hope no one decides to chain to that method.

5. If Present. Get.

if (myOptional.isPresent()) {
  var myValue = myOptional.get();

This one is a little bit trickier, and I always see it in production and in merge requests, but I don't tend to get as tufted (or not as tufted as Brian Goetz). Logically, it makes sense; you're doing the due diligence to check if your value is present, and if so, you retrieve it. Instead, understand your domain, and decide when it is best to return a default value or throw an exception:

var val = extremelyHelpfulMethod(arg).orElseThrow(() -> new FieldNotFound());


Avoid these bad practices, and if you want a great talk on how to use Java's Optional properly, watch Stuart Mark's presentation.

© 2021, Johan Oakes